[Music] Okay, just let me know if the AB is fine and uh we can get started and all that. I have no idea. So we are all, we don't know what's going to happen. Uh, so let's prepare for the worst. Even if the exam is there, which even I, I, I, I believe that I also would advocate at least for the people who are living, for the people who are living close to the border. So I would say it should get postponed, but we should, we should be preparing for it. Yeah, admit card. People have traveled to the centers and still it got cancelled. So that is not a big deal.

Okay. Okay, guys, welcome all of you. So, uh, let's get started. As you know, these sessions are a little longer. So I think we should not be taking up any time further. Last time we started, I guess we just went with the first two slides and it got stuck. So I, I will start it again from the beginning itself. The sequence would be that I'll be starting with the embryology, followed by I'll be going to the limbs, and then head and neck, neuro, and, uh, abdomen part. And histology slides kept in between because, you know, it gets a little monotonous if you read histology at one go only. So like couple of slides in between, between head and neck and neuro, between neuro and abdomen, like that. So that's how we're going to approach it.

Needless to say, you people are attending this one-shot session from last one week. I'm sure it will be very exhaustive. But I'm very sure that it will be very productive also because in the shortest span of time, you can cover up almost all the important things. So, uh, it's a little unfair to ask this question that is one shot enough? Well, enough is not enough in itself. But yeah, I mean, you, you have to, the one shot will at least comprise of all the topics which you cannot leave and go to the exam. You, you have to go through this. And while formulating this PowerPoint for you, we, I obviously, I have kept in mind that what are the recent questions which are being asked and how they can kind of, you know, twist the language of the question. So I'll kind of discuss that about in between these, you know, um, what do you say, during these lectures. It's, it's quite, uh, uh, and during these lectures, this is, it's a little difficult to kind of keep a track of, of what live chat is going on because there are too many people message me in between. So I'm really sorry if I miss any message in between. But, um, I, I will tell you the way to communicate to me so that even after the one shot, you can, you can, we can still stay in touch and I can clarify your doubt.

So let's get started. So guys, in the embryology, let's first start with the this section of the embryonic, embryonic plate, which, which has been asked already in twice in the exam last year and even last to last year, they asked this question. So, um, you know, there are certain questions in anatomy which are very terminal questions. Once they ask that question, that's it, end of it. What is a nerve supply of the following muscle? Once they ask this question, this question is over. Or about any branch of any artery or something like that. But obviously, there are certain topics which are not going to end at that point. For example, when you look at this picture, there's so much to ask on this. They have already asked the questions on neural crest cells and paraxial mesoderm. But this image is at least holding like 20 more questions inside. So they can again put this image in front of you, but obviously the question is going to change.

So what you're looking at, you're looking at a cross-section through the neural tube. What you can see the three germ layers there: endoderm, ectoderm, and mesoderm. That light green colored structure that you see over there is a notochord. Notochord. If somebody asks you, notochord is made up of what? It is made up of mesoderm. But what mesoderm? It's an axial mesoderm. Please listen to me carefully. It's axial mesoderm, not paraxial. Axial midline mesoderm thickening is forming the notochord. What cord is going to do, guys? Notochord is going to stimulate the ectoderm and convert the ectoderm into neuroectoderm and then the neuroectoderm folds to form the neural tube. As you can see the neural tube there, and we do have the cells which is present at the junction of the neural tube and ectoderm. These are called as neural crest cells. Well, which is also called as a fourth germ layer, the neural crest cells. And in the electron microscopic image, you do not expect to see the neural crest cells better than this. Reason being, neural crest cells are derived from the same neuroectoderm only, from the crest of the neural fold itself. So there is no visible difference between them. So what I'm trying to say that if they ask you the derivative of the neural tube, they will make sure that the arrow is placed on the neural tube. But if the arrow is placed somewhere at the junction of the neural tube, upper part of the neural tube and the ectoderm, then obviously they're asking about the derivative of neural crest cell. I tell you this because when this question was asked couple of years back in the exam, many people thought they're asking the derivatives of neural tube. Well, why would they do that? Why? If, if they want to ask the neural crest cells, they will put the arrow at the junction. Otherwise, they put there's a big neural tube. You can put the arrow anywhere.

At the same time, when the neural tube is being formed, this mesoderm is going to divide into three parts. That is a paraxial mesoderm. We have an intermediate mesoderm which is in between, and we got a lateral plate mesoderm. And this lateral plate mesoderm is further going to divide into two parts, that is into the, uh, the somatopleuric lateral plate mesoderm and splanchnopleuric lateral plate mesoderm. That I'm going to tell you about here. Uh, just one quick thing in between, guys. How many questions from anatomy? Honestly, nobody can define that. This is, this is very unfair to say that how many questions from that particular topic because it's, it keeps on changing. It's very dynamic. I would say INIC that is more concentrating into anatomy, especially the embryology and neuroanatomy part compared to the NEET exam. But guys, I mean, who knows better than you people that you cannot just afford to miss out any on any of the subject here. So it is as important as any other subject and it goes the same for all the 18 subjects. So just don't worry about the number of questions. The point is how many percentage of questions I'm going to get it right. Thus question I, B question, I, your, your, you know, strike rate should be above 80% in the anatomy. I mean, and, and because there's no big science behind it. The very, you know, these topics are being asked over and over again. People don't realize them because it's the same thing. It's the same thing which they quote in the different, you know, in the wrapper and then gave it to you. Otherwise, what could be new in anatomy? It's the same subject which was like 50 years back, the same anatomy today. So nothing changes. It's just the language of the question is twisted so dramatically. It looks like a new question every time. It's never new. It's always the same thing which is being asked. You just have to be a little smart enough.

Okay. So guys, back to the topic. So what I was saying now, look at the intermediate mesoderm first. Now, that small part in between is intermediate mesoderm. You don't even realize that it's intermediate mesoderm, to be honest. So that, that's why I believe that if they're asking a question on intermediate mesoderm, I'm pretty sure that they're going to highlight it and show it to you because look at the other side here. Can you identify where is intermediate mesoderm? Well, very difficult, right? Paraxial mesoderm and lateral plate mesoderm, we already saw. It's very easy to identify them here. Now, as you can see that intermediate mesoderm, first of all, the intermediate mesoderm is going to give rise to the urogenital system. Now, I'm going to talk about this urogenital system in a while, but when I say urogenital system, what I'm talking about? I'm talking about gonads like testis and ovary, and mesonephric duct and paramesonephric duct. So all the urogenital system, it is heavily contributed by the intermediate mesoderm. So let's keep this intermediate mesoderm aside for now. As I said, it will give rise to genital ducts. It will give rise to the mesonephric, paramesonephric duct, the derivatives. We'll come to it. We'll come to it. Forget about it for now. We focus on paraxial and lateral plate mesoderm because if you know the paraxial mesoderm, you automatically know about the lateral plate mesoderm. The paraxial mesoderm, it will give rise to the ball-like condensation along the entire length. And those ball-like condensation are called as somites. I'm sure you have heard the word somites or somatic. The somites are the ball-like condensation. As you can see in the center, guys, that is, let me just put a laser pointer there. If you look at that, this is the neural tube here in the center. Can you see this? That's a neural tube. It's a cranial neuropore above. That's a caudal neuropore. Below. That's a neural tube. And on the side of the neural tube, that is a paraxial mesoderm. And these thickenings of the paraxial mesoderm are called as somites. Even if it's an image-based question, I'm sure you'll be able to identify it like this only. These are called as somites. What are the derivatives of somites? And when you think of derivatives of somites, you also need to keep an eye on what is not derived from somites because whatever is not derived from somites will be derived from lateral plate mesoderm. So it's very easy. You can compare the paraxial and lateral plate with each other.

Now guys, somites can be divided into three parts. We have a dermatome, sclerotome, myotome. Like dermatome part of the somite will give rise to dermis, but dermis of only back, only back dermis is derived from it. Here, axial skeleton. Axial skeleton, that is ribs and vertebrae. Ribs and vertebrae is derived from the, the, the somites only. And ribs was one of the question asked in the recent time, guys. Last year, question was ribs only. The ribs is derived from which of the following mesodermal structure? And that was paraxial mesoderm or somite is the answer to that. And it will also give rise to the skeletal muscle. But remember, guys, when I say skeletal muscle, we are talking about skeletal muscle elsewhere in the body. But majority of the skeletal muscle in head and neck are derived from pharyngeal arches. I'm sure you know this. What is the specialty of the head and neck? Developmentally, the head and neck specialty is that the skeletal muscles like mastication muscle, facial muscle, palate, pharynx, larynx, all these muscles are derived from pharyngeal arches. Only extraocular and tongue muscles, especially tongue muscles, they are derived from somites. But when you think of the rest of the body, upper limb muscle, intercostal muscle, abdominal muscle, pelvic muscle, lower limb, core muscle, all muscles are derived from somites only. So the thing is that if dermis of the back, axial skeleton, and skeletal muscles are derived from the somites. So whatever is left is derived from lateral plate mesoderm. Now, whatever is left. Now think about, first make a list in your head, what is left. What is left, guys? We still have to form the dermis of the front and dermis of the limbs. Number two, we have to form the, what muscles? Smooth muscles and cardiac muscles. Right? Smooth and cardiac muscle. And we also need to form what skeleton? Appendicular skeleton. Axial is done. Upper limb and lower limb bones are to be derived here. And that will be derived from where? Lateral plate mesoderm. But here's the catch. Even in lateral plate mesoderm, I hope can you appreciate if I, if I show that laser pointer there. Can you see that over there? Guys, please look at the screen here. There's a coelom over there that is called as an intraembryonic. And that intraembryonic coelom divides the lateral plate mesoderm into the somatopleuric layer and the splanchnopleuric layer. So the one above is somatopleuric lateral plate mesoderm, and the one below is splanchnopleuric lateral plate mesoderm. So we already know that what is derived from lateral plate mesoderm. The question is, which one is from somatopleuric and which one is from splanchnopleuric? Somatopleuric lateral plate mesoderm will give rise to the dermis. What was the dermis left, guys? Dermis of the front and limbs, and what skeleton? Appendicular skeleton. Upper limb and lower limb bones are derived from here. Whereas splanchnopleuric lateral plate mesoderm will give rise to what? It will give rise to the, what muscles? Smooth muscles and cardiac muscle. Although cardiac muscles are derived from the cranial end of the embryo, it's a specific site for that. But yeah, at least I can broadly I can say that the cardiac muscles and skeletal, the smooth muscles, they are derived from the splanchnopleuric lateral plate mesoderm.

Okay, see you asking me the highlight the topic for the INIC NEET. It's pretty simple. Embryology and head and neck. I would say even because neuroanatomy is equally important for both NEET and INIC. But but embryology and head and neck INIC love to ask questions from there. And nerve injuries, guys, peripheral nerve injuries here. And rest, whatever we're discussing in one shot, everything is important. Rest is like, it's more focused towards the, the NEET part here. But you know, I would sincerely suggest you that especially when the content is squeezed to 5 hours or 4 and a half hour thing, I don't think that you should be doing more selections in between that. Like, you, at least one, you cannot leave anything from this. If there is anything additional, I, I'll let you know.

Okay, moving on. So intermediate mesoderm, just keep it aside. And the paraxial and the lateral plate mesoderm that you need to compare. Now, guys, you might be having this PDF with you. Now, I requested this to you last time also, and I'm again sincerely requesting you, please close it. Disclose that folder or file or whatever that you have, or if you have taken the Xerox of that, just keep it aside because if you're looking at the slides already, you're not going to anticipate anything. I want you to please anticipate what is going to come next. And that's why it's very important to keep your mind blank, look at the picture, and that's how you can fall back to your notes that what we read and how can we correlate here. Then it will not be, you know, you will not be able to anticipate what is going to come next. Sir, moving on.

Now we talked about the mesoderm, the paraxial, intermediate, and lateral plate mesoderm. Now, as we said, notochord will give rise to neural tube. Notochord will, is going to stimulate the ectoderm to form neural tube and neural crest cells. Now, what are the derivatives of the neural tube and neural crest cells? And moreover, what about notochord? Cord's job is done. So once the notochord's job is done, some remnants of notochord are there, and those remnants are present in the midline of the body. When I say midline of the body, guys, there is one called as the apical ligament of dens. Dens is the second cervical vertebrae, or odontoid process. Second cervical vertebrae extension is called as dens. So there's apical ligament of dens. There is, uh, nucleus pulposus. I'm sure you know that intervertebral disc can be divided into two parts, is nucleus pulposus. So nucleus pulposus, and number three is membrana tectoria or tectorial membrane. Membrana tectoria or tectorial membrane. Look at the laminate here. So notochord's job was to stimulate the ectoderm to convert it to neuroectoderm. But whatever is left from that is nucleus pulposus, apical ligament, and membrana tectoria, tectorial membrane. I would say out of these three, especially nucleus pulposus is the most important. But which I feel personally that nucleus pulposus, that is the one that is usually given in most of the books. And rest two are also the remnant, but they are not usually, they don't talk about them. Nucleus pulposus is the most important remnant of the, of the notochord.

What about the neural tube and neural crest cells? Now, when you think of the neural tube derivatives, guys, in the neural tube derivatives, just think about the central nervous system, CNS. Central nervous system. If you're able to correlate that structure that you're looking at with central nervous system, then means you're thinking right. Now, look, brain and spinal cord, obviously, central nervous system. Oligodendrocytes, they will do myelination for central nervous system. Astrocytes, forming blood-brain barrier. Ependyma. What is ependyma, guys? Lining of the ventricles is ependyma. Retina. Retina is an extension of the optic stalk only. So if you look at that list over there, that is all about the central nervous system or the supporting cells of central nervous system. So they are all derived from the neural tube.

What about neural crest cells? When you think of neural crest cells, see the, the easy way to deal with the neural crest cells. Though not everything will be covered in that. But still, when you think of neural crest cells, majority of the derivatives of neural crest cells can be answered by thinking about two, two things. One, peripheral nervous system. If you can correlate that given option with a peripheral nervous system, it is definitely derived from neural crest cells. Peripheral nervous system means ganglion or nerves or the myelin sheath or whatever. Okay. And number two, the structures which are present in head and neck and they look mesodermal. Now, please understand, majority of the structures in head and neck which looks mesodermal to you, for example, bones, what do you say, the, the dermis and the dentine, anything, cartilages, which, but if they're present in head and neck, there are very good chances that they're derived from the neural crest cells. Now, while looking at the option, if you're able to convince your brain that the given option is either belonging to the peripheral nervous system, or this structure belongs to head and neck and looks mesodermal, that means you're looking at neuroectoderm derivative. That's a very good chance in that. Look at that. When you say all ganglia, ganglion, any ganglion, whether it's a sympathetic, parasympathetic ganglion, sympathetic chain, otic ganglion, dorsal root ganglion, whatever it is, if the name says ganglion, it is derived from neural crest cells. Probably the only misnomer here is the basal ganglia, because basal ganglia is not a ganglion, it's nuclei. Enteric plexus, myenteric plexus, submucosal plexus, or Auerbach's plexus, they're all from the neural crest cells. Cells. Myelination, Schwann cells will do the myelination for peripheral nerves. Adrenal medulla. I hope you know adrenal medulla is having the chromaffin cells, and these chromaffin cells are nothing but the modified sympathetic ganglion only, modified sympathetic ganglion. Look at the word, when I'm saying ganglion. Melanoblast. Look at the skull bone, guys. Most of them. Some exceptions are there, but most of the skull bone, except the occipital bone, is coming from the somite. Then dentine, pharyngeal arch cartilage, dermis of head and neck, cementum. If you look at these, this, this, these derivatives here, they look mesodermal, but they're in head and neck. So that mesenchyme of that head and neck is actually derived from neural crest cells only. So despite there's a, there's a very long list of neural crest derivatives, just go with the peripheral nervous system, or just go with the, what do you say, the head and neck structures which look neural to you.

Moving on. Okay, that was about this, that picture, guys, and the derivatives. I believe that's a very important juncture and from where the questions are still yet to be asked. Question, that section of the embryo and the derivatives from there can still be asked in the exam. Very good chances, and especially INIC, because they love to repeat the topics.

Okay, development of diaphragm. Diaphragm development. I'm pretty sure that you must have seen these questions multiple times at different places. Now, diaphragm is derived from four sources. It's important to identify those sources or those structures on the picture. What you're looking at right now, look at the posterior lateral, guys. It's a developing diaphragm. So don't try to relate this diaphragm with a, with an actual gross anatomy developed diaphragm. It's a developing diaphragm. So what you're looking at there is a body wall mesoderm. Now, body wall mesoderm, which is like right now in the picture, can be seen posterior laterally. What is body wall mesoderm? It's a cervical somites only. It's a mesoderm. It's, it's a paraxial mesoderm only. Cervical somites or body wall mesoderm, and that will give rise to the muscles of the diaphragm. Muscular part of the diaphragm will be derived from this body wall mesoderm, or you can say cervical somites. Second thing is a dorsal mesentery of esophagus. Now, esophagus is not having any mesentery. Mesentery, mesentery is with the stomach. Mesentery is with the intestine. Mesentery is with the colon, mesentery is with the sigmoid colon, appendix. But there is no mesentery of esophagus. There was, there was mesentery of esophagus also. And that dorsal mesentery of esophagus is absorbed to give rise to the crura of the diaphragm, or you can say crura of the diaphragm. The crura or the crura of diaphragm is by the dorsal mesentery of esophagus. Number three, septum transversum. The most important septum transversum is the most cranial structure in the embryonic plate before the folding of the embryo. And once the embryonic folding takes place, the septum transversum will come like more in the anterior area here. So in the developing diaphragm, the most anterior structure that you're looking at over there, that is septum transversum. Although it will give rise to the central tendon of the diaphragm, which eventually will go toward the central part here. That's a central tendon coming from septum transversum. And look at the dark pink color over there, guys. That is called as a pleuroperitoneal membrane. It's a thin membrane which is separating the pleura and peritoneum. We call it a pleuroperitoneal membrane. Now, this pleuroperitoneal membrane. Now, there are two fates to it. Number one, the pleuroperitoneal membrane is formed, but this pleuroperitoneal membrane is not incorporated by the muscle. The muscles are not going to invade this pleuroperitoneal membrane, and that failure of the migration of the muscle into this, into this pleuroperitoneal membrane, that will cause this membrane to stay very, very thin, and that is called as an eventration of the diaphragm. One condition is that pleuroperitoneal membrane is not present. If pleuroperitoneal membrane is not present, if it, it is absent completely, then it is going to give rise to the opening, and that is a Bochdalek opening or Bochdalek hernia, and that is congenital diaphragmatic hernia. Guys, I'm sure you all know about congenital diaphragmatic hernia, which is more common toward the left side, and that is basically because of the, uh, this absence, absence of the pleuroperitoneal membrane. We said there is a second condition. The pleuroperitoneal membrane, to this pleuroperitoneal membrane is not invaded by the muscles. It is not incorporated by the muscle. If the muscle fails to incorporate this, then a thin membrane will be there, which is separating the thoracic cavity and the abdominal cavity, and that still is not able to stop the intestine to coming into the thoracic cavity. That is the eventration of the diaphragm. The eventration of the diaphragm. They've asked this question about the pleuroperitoneal membrane absent multiple times. I very strongly feel they can ask you the question like this that pleuroperitoneal membrane is present, present to here, but it is not incorporated by the muscle, then what condition it can give rise to? That is eventration of the diaphragm. Eventration. We'll come to that. We'll let's reach there, you know, eventually.

Okay, pharyngeal arches. Now, pharyngeal arches. If in the entire embryology, guys, if I have to suggest that you just want to kind of revise, you know, you want to revise embryology and there is a choice given to you, want to revise only one topic in embryology, please go with this. Close your eyes and just go with the pharyngeal arches. Everything about pharyngeal arches. This is important. I can keep this topic as the, as, as a topmost priority in the anatomy, that is pharyngeal arches. But when I say pharyngeal arches, it's about everything. Ectoderm, endoderm, mesoderm, pharyngeal arch, arteries. Everything about pharyngeal arches is important. Okay.

Now, what you're looking at right now, you can see 1, 2, 3, 4, and 6 arch. Needless to say, fifth arch disappears. And I hope you are able to appreciate that there is a, the red color which is shown on the inside, that is the endoderm. And the green color on the outside is showing the ectoderm. And then obviously the orange color inside basically showing the mesoderm. You can see that that second pharyngeal, the ectoderm of the second pharyngeal arch is overgrowing. And that ectoderm of the second pharyngeal arch, it's, if I may, it overgrows like this and will go down and come below, and that's how it leaves an embryological space over there, which is called as a cervical sinus. The cervical sinus. All the clefts are closed, guys. All the spaces on the outside are closed. So second cleft, third cleft, fourth cleft, clefts. The clefts are not there, and the space is called a cervical sinus. The cervical sinus eventually disappears. But if the cervical sinus persists, I'm sure you all know that it can give rise to a branchial cyst. That can give rise to a branchial cyst. That usually it's a painless, harmless swelling that we have along the sternocleidomastoid. That is a, the branchial cyst. The only cleft which is left is the first one. First cleft is the only cleft we have. And that first cleft, I mean, look at the head and neck, guys. The only opening that we have on the side is the external auditory canal. So first cleft is the only cleft we got, and that is going to give rise to the external auditory canal and even the outer layer of tympanic membrane. Outer layer of tympanic membrane. Now, some new, you know, updates are also there in this that it's not just the first cleft, even the first pharyngeal arch, first arch also contributes to the external auditory canal. Right? So I'm just saying, let's say if they want, if, if first cleft is given in the option, please go with it. But if first cleft is not given and first arch is given in the option, you can also go with that as well. It is mentioned in the latest language as well that the first cleft and even some part of first arch also contributes to the external auditory canal and the outer layer of tympanic membrane.

The space on the inside, that is endodermal spaces. I'm sure you all know that those endodermal spaces are called as what? Pouches. As you can see, the first pouch, which lies between first and second arch. Well, what this will give rise to? It's quite easy. If the first cleft is giving rise to the outer layer of tympanic membrane and external auditory canal, the first pouch will give rise to the inner layer of tympanic membrane. And just go from there only. Like, inner layer of tympanic membrane is facing toward the middle ear cavity, and the two extensions of middle ear cavity are Eustachian tube and mastoid antrum, and they both are derived from the first pouch. So inner layer of tympanic membrane, tympanic cavity, auditory tube, and mastoid antrum. The second pouch, the second pouch will give rise to the palatine tonsil. Although it is believed that the lymphoid present in the palatine tonsil is derived from neural crest cells. If they want to ask this in more detail, palatine tonsil is derived from second pouch, that is correct. But the lymphoid present in palatine tonsil is actually derived from neural crest cells. Third pouch, guys. Third pouch is the one which is, which is quite important, I would say, based on the question asked in the recent time. Third pouch will give rise to the thymus and inferior parathyroid gland. Whereas a fourth pouch will give rise to the superior parathyroid gland. Here, that, that sounds a little opposite here. But superior is from fourth pouch, and inferior is from the third pouch here. Fifth pouch, we do not have fifth pouch because the fifth arch disappears. So we do not have fifth pouch. But we have some remnants of fifth pouch, which are called as ultimobranchial body. And that was you were talking about Abhishek, that ultimobranchial body is the one, uh, it is basically ultimobranchial body is invaded by the neural crest cells, and that is the one which is going to give rise to the, the parafollicular C cells. So if the question is asked to you that C cells are derived from where, definitely neural crest cell is a better answer than ultimobranchial body. I'm sure you also read about this in your pathology also that third pouch and fourth pouch anomaly, guys, the microdeletion syndrome, the DiGeorge syndrome. So if, and this was one of the image-based question asked that if there is an absent or if there is a maldevelopment of the third pouch and fourth pouch also, especially third pouch, then it can give rise to the DiGeorge syndrome, that is absent thymus and hypoparathyroidism. Guys, DiGeorge syndrome, the microdeletion syndrome, like 22q11 deletion syndrome, that is the DiGeorge syndrome, right? Okay, so that is about the clefts and pouches. Cleft, only first cleft is there. Pouch, all of them there. And then you're looking at the derivatives of all these pouches here.

Okay, moving on to the pharyngeal arch cartilages. Now, now it's, it's, it's a picture that you need to keep it in your mind. Obviously, it's not easy to remember everything in the exam. You just have to keep this picture in your mind, guys. First arch. Now, there is a cartilage that you see in the first arch. This hyaline cartilage model is called as a Meckel's cartilage. Meckel's cartilage. And this Meckel's cartilage is the one which is a cartilage of the first pharyngeal arch. But Meckel's cartilage gives rise to what? It gives rise to the malleus and incus. I'm sorry. Let me go back. The Meckel's cartilage is the one which will give rise to the malleus and incus. Meckel's cartilage is not giving rise to mandible. Mandible is derived from first arch. That is true. But that is not derived from Meckel's cartilage, guys. Meckel's cartilage to hyaline cartilage. Hyaline cartilage will ossify and give rise to the bone. And majority of the skull bones are not derived from the cartilages because they are from membranous ossification. The flat bones, flat bones will be from membranous ossification. So it is right to say that whatever derivatives we have from Meckel's cartilage is derived from first arch, but not necessarily every derivative of first arch is coming from Meckel's cartilage. So simple about first arch, that orange color over there, first arch will give rise to Meckel's cartilage, and the bones coming from there is malleus and incus, like from the Meckel's cartilage itself. Second arch will give rise to stapes. I'm pretty sure that you all know about this exception also that stapes, except the footplate of the stapes, the footplate of the stapes and annular ligament, they are derived from the otic capsule. They are derived from the otic capsule. So it's, it's the stapes that is correct, but not the footplate of the stapes. Remember that here. Rest everything is fine, guys. Styloid process, stylohyoid ligament, lesser cornua, small part of the upper body also, it is all coming from second arch. The blue color is for the second arch here. Third arch will give rise to what? The greater cornua of the hyoid bone and the lower body of the hyoid. This lower part of the body and the greater cornua of the hyoid bone, it is derived from the, the third arch. And fourth and sixth arch. Fourth and sixth arch collectively are giving rise to laryngeal cartilages. The reason I keep recommending that don't do them separately because every book is having a different opinion on that. So I would that whether it is thyroid, cricoid, whatever, all the laryngeal cartilages are derived from fourth and sixth arch collectively. Collectively from fourth and sixth arch, that is laryngeal cartilage. Yes, question recurs cartilage. I mean, second arch cartilage, first arch cartilage is Meckel's cartilage. Second arch cartilage is called as Reichert's cartilage, and that Reichert's cartilage is the one which will give rise to the stapes and styloid process, stylohyoid ligament. So you're right.

Okay, pharyngeal arch arteries. Now, talking about pharyngeal arches, how can we miss the pharyngeal arch arteries, guys? So I'm sure that many of you attended my class, so you probably remember it. It's a recap. So, but for the recap, I need to first tell you, take you to the basics of that here. Guys, to understand the pharyngeal arch artery, see, in the developing embryo, we have two dorsal aortae. Aortae. There are two dorsal aortae. So we have a right dorsal aorta and we have a left dorsal aorta. You are looking at the two dorsal aortae, right and left dorsal aortae, guys. Please look at the screen. Please don't look into your notes because you will see every step happening here, and that's why I want to please focus on the screen here. Then dorsal aorta is present on the dorsal side. More ventrally in the developing thoracic cavity, more ventrally, we have a heart tube, and the cranial part of the heart tube is called as a truncus arteriosus. I hope you all remember that word, guys. Truncus arteriosus. The truncus arteriosus is having an extension, and that extension is called as an aortic sac. And that aortic sac divides into the right horn and the left horn of the aortic sac. That's looking at the aortic sac there. And there is a right horn and the left horn of the aortic sac. Right and the left horn of the aortic sac. They need to connect to the dorsal aorta. And how do we connect them to the dorsal aorta? By pharyngeal arch arteries. How many pharyngeal arch arteries? How many pharyngeal arches we have? We have six pharyngeal arches initially. Fifth one disappears, but initially we have six pharyngeal arches, and that's why we have the six pharyngeal arch arteries, which are connecting these two horns of the aortic sac to the dorsal aorta. So that's the, that's the first, second, third, fourth, fifth, and the sixth pharyngeal arch arteries. One more important thing we need to know before we go to the arterial development. There are multiple branches coming out of the dorsal, guys. I mean, branches like we have here, here, here, here, like this. But there is one which I need to focus on, and that is the seventh cervical intersegmental artery. Whether it's on the right side or left side, there is something called as a seventh cervical intersegmental artery. Why the seventh one is so important? Because seventh cervical intersegmental artery will go into the upper limb. It will become subclavian, axillary, and then eventually brachial, radial, and everything. That's why the seventh one. So all I'm trying to say that seventh is not the only artery we have. We have other arteries also above that and below that. But the seventh one you need to focus on. Seventh cervical intersegmental artery. It has some role to play. We'll come to that. So I hope you understood this image here. Now let's take this picture. Uh, Sudhanshu, I, I, I'm not going to go English on this because, you know, many of our friends are attending this session from very southern part of the country, and probably they're not comfortable in Hindi. So let's go in English. But basically, English, it's very simple English I'm speaking, you right? So that is the aortic sac, and we have the right and left horn of the aortic sac. Right? Once again, now, first let's start with the arch of aorta. When I talk about the aorta, guys, aorta or arteries, it's aorta is toward the left side, and veins are toward the right side. So when I say left side, it's the right side fourth arch artery, which is the most important. Dorsal aorta is also there, but I know that in the exam, they will just ask you that which arch artery is going to give rise to the, to the, what do you say, to the arch of aorta. So simply, the left fourth arch artery. But please make sure that don't, do not, you know, miss out on the right and left. It's left side fourth arch artery. Overall, overall, the arch of aorta is derived from where? Aortic sac is there, left horn of aortic sac, left side fourth arch artery, and some part of dorsal aorta also, that's the left dorsal aorta as well. But still, you just stick to the fourth arch artery, the left side. I can assure that is more than enough. Left fourth arch artery, arch of aorta.

Okay, of the arch branches. What are the branches of arch of aorta? We have three branches, guys. One, we have the, what do you say, the subclavian artery with subclavian, that is the right subclavian artery. Then we have, uh, sorry, brachiocephalic artery. I'm sorry. Brachiocephalic artery. Then we have the left subclavian artery and the left common carotid artery. Subclavian artery, you can already see, guys. Look at that, if I may point it out, that already is there. This is the brachiocephalic artery. I keep saying subclavian, I'm sorry, that is brachiocephalic artery. That's the brachiocephalic artery, and that is derived from the right horn of the aortic sac. That's it. Right horn of the aortic sac is going to give rise to the brachiocephalic artery. Okay. What about common carotid? Common carotid artery is derived from the third arch artery. Now, first, look at that, guys. Can you see the third arch artery? And then there's a bud coming out from there. That is the external carotid artery. Now, this here is the common carotid artery. That bud is for external carotid, and the remaining is the internal carotid artery. So it's not wrong to say that whether it is common carotid, internal carotid, external carotid artery, which arch artery is forming? Third arch artery. Exam may say arch artery. Pushing, they will mainly ask you about the arch artery. So focus on that, which number, which arch artery is that here. So whether it is right side or left side, the common carotid artery is by the proximal part of the third arch artery, and internal carotid artery is by the distal part of the third arch artery.

Okay, then let me bring that seventh cervical intersegment. I hope you remember seventh cervical intersegmental artery. Now, guys, this left side seventh cervical intersegmental artery will give rise to the left subclavian artery. Left side seventh cervical intersegmental artery will give rise to the subclavian artery. And that completes the branches of arch of aorta. Let's focus on arch of aorta. So three branches of arch of aorta there. What three branches are we talking about, guys? One branch of arch of aorta is there, that is the brachiocephalic artery, coming from where? Right horn of aortic sac. Then another branch of arch of aorta is common carotid artery of the left side. Obviously, that is coming from the third arch artery. And then we have a subclavian artery of the left side, which is coming from the seventh cervical intersegmental artery. Right? That is sorted. But the main question here is, what about the right subclavian artery, guys? What about the right subclavian artery? The right subclavian artery is by the seventh cervical intersegmental artery. That is fine. But we also need the fourth arch artery there. Fourth arch artery on the left side is forming the arch of aorta. Right side, where there is no arch of aorta, but fourth arch artery is there. So I can use that fourth arch artery also along with the seventh cervical intersegmental artery. Now, they both together will give rise to the right subclavian artery. Now, just repeat this after me. I mean, to yourself only. Right subclavian artery is mainly derived from where? It is by the right side fourth arch artery and seventh cervical intersegmental artery. Dorsal aorta is also there in between. But that major part is by fourth arch artery and the right seventh cervical intersegmental artery. Right?

Okay, then there is a development of lung buds. You can say lung buds or respiratory buds. Guys, lung buds and respiratory buds are the ones which are invaded by the sixth arch artery. Look at that, sixth arch artery is invading the lung buds. And that tells you that the proximal part, proximal part of the sixth arch artery will give rise to what? Pulmonary artery. Proximal part of sixth arch artery will give rise to the pulmonary artery. Distal part of the left sixth arch artery, very important, and a question asked in the exam recently. Guys, look at this, distal part of the only left side, only left side, not on the right side. Distal part of the left sixth arch artery will give rise to the ductus arteriosus. So it's a very important structure, obviously in the fetal circulation. Ductus arteriosus is derived from from the distal part. It's very important to say the word distal. D, distal part of the left sixth arch artery will form the ductus arteriosus. Fifth arch artery disappears. Now, we all know, guys, that the fifth arch artery, this fifth arch artery disappears. So forget about it. What about this first and second arch artery? I'm sorry. The first arch artery remnant, guys. The remnant of the first arch artery is the maxillary artery, and the remnant of the second arch artery is the hyoid and the stapedial artery. Just this remnant only. First arch artery over there, you can see that is that is the maxillary. Second arch artery here is stapedial and hyoid. Third arch artery is forming common carotid and internal carotid, external also. Fourth arch artery is forming arch of aorta and right subclavian. Fifth arch artery, degenerate. Sixth arch artery is forming what? That is forming the pulmonary artery, and it is also forming the ductus arteriosus. So it's not difficult. It's easy peasy lemon squeezy. Push. I'm not, I, I guess I'm not, I'm not saying anything which is, uh, beyond which is not what is not written in the slide. So what are you saying? I, I hope that when you look at this summary, you can make out that what we just saw in the previous picture, it is all there on the slide now. So I, I'm, I'm not going to say anything extra beyond the slides. But, uh, you know, if you find anything that you're not able to understand, please let me know.

Okay, now about the two important anomalies, guys. Now, I just, just look at this picture. Look at the red color over there. The red color here, it is first showing the seventh cervical intersegmental artery of the left side, which forms subclavian artery. And here is a fourth arch artery. Fourth arch artery and seventh cervical intersegmental artery forming subclavian of the right side. The question is, if the fourth arch artery of the right side disappears or obliterates, if the, if developmentally fourth arch artery of the right side obliterates, then what will happen? Bloody, because fourth artery is obliterated. So now what will happen? This portion of dorsal aorta, the caudal part of the right dorsal aorta will persist. Look at that, the caudal part of the right dorsal aorta will persist, and that will give rise to the aberrant right subclavian artery. It's very important to say first that which arch artery obliterates? Fourth arch artery. If the fourth arch artery is obliterated, and then there is a persistence of caudal part. After that, if there is a persistence of caudal part of right dorsal aorta, that will give

Rise to the aberrant right subclavian artery, and this aberrant right subclavian artery is going behind the esophagus, causing dysphagia. Look at the artery over there, guys. That's the aberrant right subclavian artery coming from the aorta, behind the esophagus, compressing the esophagus and causing dysphagia. Okay.

What about if the question is now, it's very, very, very close to each other. If the question is about that fourth arch artery, is there it is not obliterated. Fourth arch artery is there, and despite having the fourth arch artery, you still have the persistence of the caudal part of the right dorsal aorta. Look at this picture now. So you have the fourth arch artery, and now you also have the caudal part of the right dorsal aorta. Now, what condition will this be? Now, this condition is a double aortic arch. So, without any obliteration, if there is a persistence of the caudal part of the right dorsal aorta, this will give rise to the double aortic arch. And the problem with the double aortic arch is this aortic arch is present. I'm sorry. This aortic arch is present around the trachea and esophagus. It compresses the trachea and esophagus from, like, surrounding it here. And that is not only causing dysphagia, it is causing dyspnea also. It's a vascular ring. There's a vascular ring present around the trachea and esophagus that is, yeah, that is causing the dysphagia as well as dyspnea as well. So it's very close. They've already asked the question about the aberrant right subclavian artery. I very strongly feel that double aortic arch could be asked in the exam. So it's a very, very small thing to remember that for the aberrant right subclavian artery, the fourth arch artery is obliterated. Double aortic arch and nothing is obliterated, but still there is a persistence of the caudal part of the right dorsal aorta, and that's why we have a double aortic arch. Okay. So this was about the arterial development.

Sorry, now let me tell you a little about the misogastrium. First, venous development. Now, when I say misogastrium, this is also a question asked in the recent time, guys. The key structure here is the stomach. Look at the stomach there. This green thing that you see in front of the stomach, that is the ventral misogastrium. Whatever you see in front of the stomach, that is the ventral misogastrium. Whatever you see behind the stomach or along the greater curvature, that is the dorsal misogastrium. Ventral misogastrium is derived from the septum transversum. And dorsal misogastrium is basically coming from the lateral plate mesoderm. So, just don't worry about that. Question: What are the derivatives of the ventral and dorsal misogastrium? And the easiest thing is to think about that the liver is developing inside the ventral misogastrium. That's the liver there. And the spleen is developing in the dorsal misogastrium. And you'll get all the hint because if the liver is developing in the ventral misogastrium, guys, what is the ligament which is connecting the liver? What is it? The ligament which connects the liver and the anterior abdominal wall, that is the falciform ligament. The ligament connecting the liver and the stomach is the lesser omentum. The ligaments which are surrounding the liver are called as the coronary ligaments and triangular ligaments. So, all of them are the derivatives of the ventral misogastrium. It's pretty simple. Think about the ligaments which are surrounding the liver. Think about the ligament which is connecting the liver to the anterior abdominal wall, the falciform ligament. And think about the ligament connecting the liver to the stomach, that is the lesser omentum. They're all derivatives of the ventral misogastrium. Similarly, for the dorsal misogastrium, just think about all the ligaments present along the greater curvature. Now, as you can see, the fundus of the stomach will be connected to the diaphragm via the gastrocolic ligament. Then we have a ligament present here connecting the stomach and the spleen, that is the gastrosplenic ligament. The spleen is connected to the posterior abdominal wall where the kidney is present. The left kidney is present. That is the lienorenal ligament. And then, obviously, it is the greater curvature of the stomach. So, we have what omentum here? The greater omentum. So, I can say gastrocolic, gastrosplenic, lienorenal, and greater omentum. They're all derivatives of the dorsal misogastrium. Falciform ligament is something which is already asked in the exam, guys. This is already, this is an image-based question asked in the exam. You can see how many options the examiner still has. They can give you an image-based question. Make sure you point out the structure correctly, especially where is the ventral and where is the dorsal misogastrium, and you can easily make out what are their derivatives. Perfect.

Okay, moving on. And one more thing here, there is something which is a content of the falciform ligament. Only the falciform ligament is like a double fold, only guys. Below, in the lower part of the falciform ligament, can you see that ligament, guys, over there? That is the ligamentum teres. Ligamentum teres is a content of the falciform ligament. It is a content. It is present in, in between, inside the falciform ligament only. And this ligamentum teres is nothing but the obliterated left umbilical vein. You all know that the left umbilical vein is functional before birth, but after obviously birth, the left umbilical vein, only the remnant will be there, and that is nothing but the ligamentum teres.

Ligamentum teres. Coming to the venous development from the arterial development, let's move on to the venous development now. Now, again, for the venous development, guys, let's first look at these, you know, the raw material that we have. The vein coming from the upper part of the body, carrying the blood in the embryo from the upper half of the body, is called the anterior cardinal. So, we have the right anterior cardinal vein, left anterior cardinal vein, right posterior cardinal vein, left posterior cardinal vein, which are carrying the blood from below. And then we have the common cardinal vein, into which they are draining. Like, look at this. Can you see the anterior cardinal vein coming from above, posterior cardinal vein, and they're taking the blood into the common cardinal vein? With the development of the kidney, now kidneys, they will start developing. And can you see the small veins that, that you can see coming out of the kidney? These are called the mesonephric veins, guys. These veins, these small veins over there, are called the mesonephric veins. From the posterior cardinal vein, a vein will come, will collect the blood from the kidney, and will go and join back the posterior cardinal vein only, and that will be called the subcardinal vein. You can see the right and the left subcardinal vein. Their job is to take the blood from the developing kidney. We call them subcardinal veins. Right subcardinal, left subcardinal. More veins will develop. Then we have another vein developing on the posterior abdominal wall, and that is called the supracardinal vein. This is subcardinal. Now we have a supracardinal vein. We also do have an anastomosis in this region, guys, that is called the intersubcardinal anastomosis. Look at this animation again. That anastomosis, or called as, called the intersubcardinal anastomosis. And look at that another vein developing now, there again, coming from below and joining to the posterior cardinal vein only. That is called the supracardinal vein, guys. This vein is called the supracardinal vein. Supracardinal vein. Now, this is what we have with us, guys. Anterior cardinal, common cardinal, posterior cardinal, subcardinal, supracardinal, intersubcardinal anastomosis. Just, just keep this picture in mind. And based on that, let's talk about the major venous development here.

Okay. What are you looking at, guys? Now, I've just kind of put those these veins in the background so that we can only highlight the veins which will give us something. Now, look at the vein which I just highlighted to you. It's a vein which is carrying the blood from the right side of the head and neck region. It's basically the right brachiocephalic vein. So, I can say that the brachiocephalic vein of the right side is derived from the right anterior cardinal vein. It's the right anterior cardinal vein. The right brachiocephalic vein will be formed by the left anterior cardinal vein. Need to take the blood toward the right side. You know, superior vena cava and inferior vena cava are present toward the right side. So, obviously, I need to shift this blood toward the right side, and for that, I will need an oblique anastomosis. So, I can say that the right brachiocephalic vein is just by the right anterior cardinal vein, but the left brachiocephalic vein is by the left anterior cardinal vein and this anastomosis, called as an oblique anastomosis, is called as an oblique anastomosis. Please keep reading simultaneously on the side. So, right brachiocephalic vein, guys, that is only by this right anterior cardinal. Left brachiocephalic vein is derived from this entire thing, left vein, and this oblique anastomosis is also needed here. Once the two brachiocephalic veins join each other, they together give rise to the superior vena cava. There you have it. The superior vena cava is derived from two sources. What are the two sources you're looking at right now on the screen, guys? One of the sources, a small part of the anterior cardinal vein of what side? Right side again, right anterior cardinal vein and the right common cardinal vein. So, right anterior and right common cardinal vein together will give rise to the superior vena cava. Important one. Right anterior cardinal, right common cardinal, superior vena cava. Brachiocephalic done. Superior vena cava is also done here.

Okay. Then inferior vena cava. Let's find out the inferior vena cava first, and then we can, we can basically go to the other tributaries of the inferior vena cava. Inferior vena cava is derived from, look at the highlighter, and I want, the moment this animation comes in front of you, just start saying those, what veins are those, guys? Look at that posterior cardinal vein, right posterior cardinal vein, supracardinal vein, anastomosis, subcardinal vein, and then this subcardinal vein is going to join with something called as a hepatocardiac channel. Also, you can kind of ignore it for now. Hepatocardiac channel, basically, this here is the posterior cardinal vein of the, obviously, of the right side. Then we have the supracardinal vein, this one is supracardinal. Then there is the formation of an anastomosis. Then this is the right subcardinal vein. And then the cranial most part or the terminal part of the inferior vena cava is by the hepatocardiac channel. You can ignore the hepatocardiac channel, whatever is seen in the picture. Just compare this with the written part here. So, right posterior cardinal vein, this much there is right posterior cardinal vein over there. This is the supracardinal vein. Then we have what? Anastomosis. And this is the subcardinal vein of the right. It's all right, right, right. Everything is right on this. That is the inferior vena cava. Inferior vena cava, you got, guys? Look at this highlighter again. What are those renal veins? Right renal vein is just by the right mesonephric vein. That's a right mesonephric vein forming the right renal vein. But look at the left renal vein. It's just the left mesonephric vein is not enough. This anastomosis is also required. That is called the intersubcardinal anastomosis. Is also needed here. What connects the superior and the inferior vena cava? And that is another neat image-based question. Imagine it was a NEET PG, image-based question, that is about the azygos vein, guys. Azygos vein is connecting the superior and the inferior vena cava. Now, I'll tell you one of the common mistakes which people do is that they understand that, uh, what do you say, you know, this azygos vein is this. Well, no, this is not the azygos vein. Azygos vein is partly by this, that is the posterior cardinal vein, but the main part of the vein is by the supracardinal vein. This is the right supracardinal vein, and that's the major part of the, of the, of the azygos vein. So, look at the highlight, the animation there, that red line over there is showing that azygos vein. So, azygos vein is by the supracardinal vein, right supracardinal vein, very small contribution by the posterior cardinal vein also. So, if you have to choose between the supracardinal and posterior cardinal vein, definitely go with the supracardinal vein as your best answer. What else? Look at the vein which I'm going to highlight in front of you, guys. Gonadal veins. Gonadal veins, you know that the right gonadal vein, it goes into the IVC, whereas the left gonadal vein goes into the renal vein. So, you can look at the highlighted area. It tells you that gonadal veins are derived from what vein? Subcardinal vein. But what part of the subcardinal vein? Caudal part of the subcardinal vein. It's the caudal part of the subcardinal vein forming the gonadal vein. Whereas the cranial part of the subcardinal vein is going to form the adrenal vein. Look at those veins, that's the adrenal vein. Once again, the same story. Right adrenal vein, it drains. Right adrenal vein drains into IVC. Left adrenal vein drains into the renal vein here. So, that is the gonadal vein, and the gonadal vein is by the caudal part of the subcardinal, and the adrenal vein is by the cranial part of the subcardinal vein. These are the major veins that you need to know here. So, in this picture, you can see brachiocephalic, both brachiocephalic, superior vena cava, inferior vena cava, azygos vein, right and left renal vein, adrenal, and the gonadal vein. And I, I very firmly believe that the examiner will not go beyond this in the venous development.

Okay. So, guys, this is about the arterial development and the venous development. Now, one more thing, and then we will conclude on this embryology part. That is something which we left in the beginning, guys. Genital system, about the paraxial mesoderm and lateral plate mesoderm, but we did not talk about the intermediate mesoderm. The intermediate mesoderm is going to give rise to. Now, this whole thing is intermediate mesoderm only that you're looking at over there. That is all intermediate mesoderm. Intermediate mesoderm. In the intermediate mesoderm, one, this rounded structure that you see is a genital ridge, and then the rest is called as the rest is called as a nephrogenic cord, where we have the mesonephric duct and the paramesonephric duct. If at all it is an image-based question, the simple thing is when you find out the genital ridge, the duct which is close to the genital ridge is the mesonephric duct because the mesonephric duct is going to give rise to the spermatic pathway. Obviously, the spermatic pathway should be close to the testes. So, the duct which is close or more inside is the mesonephric duct. The more the duct is more outside, the more peripheral position, that is the paramesonephric duct.

Now, guys, what about the mesonephric duct? See, mesonephric duct or Wolffian duct. Now, in male or in female, the derivatives of the mesonephric and paramesonephric duct, derivatives of mesonephric and paramesonephric duct, they, they have some common derivatives. Like the mesonephric duct, whether it's male or female, they will get absorbed and will give rise to the trigone of the bladder. Whether it's a, it's a right side or left side, the trigone of the bladder is by the mesonephric duct. They will give rise to the posterior wall of the urethra till the ejaculatory duct. Posterior wall of the urethra, very small part of the posterior wall of the urethra. Okay. They're going to give rise to the ureteric bud, and derivatives of the ureteric bud, guys. Ureteric bud derivatives means like the entire collecting portion of the kidney. Kidney's collecting part is, is, is basically derived from here. That is the, coming from the mesonephros. So, these are common derivatives. Mesonephric duct, whether it's male or female, these are the common derivatives in from the mesonephric duct here. Now, there's a point, the mesonephric duct is more important in males because it is going to give rise to the spermatic pathway. It is going to give rise to the spermatic pathway. So, when I say spermatic pathway, think about everything, guys. Ejaculatory duct, epididymis, appendix of epididymis, here, vas deferens, everything. The spermatic pathway is entirely derived from the mesonephros. In case of female, the mesonephric duct is just having a remnant, and that remnant is called the Gartner's duct. Gartner's duct, guys. Um, people confuse the Gartner's duct with the Gartner's cyst. Please don't do that. Gartner's duct is present in the broad ligament. Gartner's cyst is present in the upper part of the vaginal wall, but Gartner's duct, duct cyst, Gartner's duct is present inside the broad ligament here. So, that's a derivative of the mesonephric and paramesonephric duct. What about the, what about the paramesonephric duct? That's the mesonephric, paramesonephric duct, the one which is shown in the blue color there. The paramesonephric duct is more important for females because it is going to give rise to most of the female derivatives, like it will give rise to the fallopian tube, the uterus, and the upper part of the vaginal wall also. So, female derivatives. Male remnants in males, we have appendix of testis, and please be careful, guys. Appendix of epididymis is a derivative or remnant of the mesonephric duct. Appendix of testis is a remnant of the paramesonephric duct. And there's something called as a prostatic utricle. Just don't bother about it. Prostatic urethra. If you look at the prostatic urethra on the posterior wall of the prostatic urethra, there is a small blind diverticulum present. And that blind diverticulum present on the posterior wall of the prostatic urethra, it is just a, it is just a homologous organ to the vagina in females, is called as a prostatic utricle. That is a remnant of the paramesonephric duct. That is a remnant of the paramesonephric duct itself here. Right, guys? So, this is about the embryology part here. Right. So, I hope it is going good so far. Just very quickly, just let me know if, if my speed is fine, if I'm able to, you know, because we have to follow a certain speed in this, you know, especially in this one short thing. So, if I'm going with a better, but don't worry about the PDF thing, that's my responsibility. What even if I'm writing a dot over there, I'll give you the same PDF to you. So, just, just no, no worries. I'm taking the lecture from my home, actually. I have a 7-month-old daughter, with a 7-month-old fighter jet of my own. Right. So, if you may hear some background noises, so please just forgive me for that. Okay. Thank you, guys. I mean, okay. Wonderful.

So, histology, guys, in between histology, we'll like we'll use it like a salt and pepper in between here because I don't want to bore you with the histology thing. Histology. I'll tell you something interesting thing about histology is in the, in the recent time, what I've noted is that, in fact, it's my recommendation to you. They can ask you anything, but in the recent time, what I've noted is that histology questions which they're asking in the exam are very basic. They're just asking you identification only. Identify fibrous cartilage, identify kidney, identify pancreas. So, something like that here. So, most of the slides I'm going to cover in here. There was a time, 2015, 16, 17, that they used to ask very detailed histology questions. It's just basic, basic identification only they ask you. So, I would say that if you have read a little less histology or if you're planning to read histology in detail, looking, it's not that. Okay, these questions were asked in PYQs 2015, that means they were asking so much of detail. No, if they want to, if they really want to screw us on the histology part, they can still do it, no matter how much we read it. So, I would say this basic identification of the slide is important. This what you're looking at right now, guys, this is a slide of a cardiac muscle. Right? That's the cardiac muscle here. Cardiac muscle. How is cardiac muscle, guys? The muscle fibers are, first of all, profusely branched. The branching can be seen. Next, I'll show you skeletal muscle. Skeletal muscles are unbranched, they're parallel bundles, but they're not branched. But you can clearly see branching over there, and that's why it's a cardiac muscle. What about nuclei? The nuclei are oval and central in position. Can you see the nuclei? The nuclei are oval and central. They're centrally located. They're not on the periphery, and they're, they're oval. They're not like flat nuclei. They're oval nuclei there. The most important thing in the cardiac muscle is, like, if, if I just may look at these three circles which I've just shown you, guys. Look at over there. This one, this one, and this one. Can you see that line over there? That is nothing but the intercalated disc. And they've asked this question earlier also. Intercalated disc is basically a functional syncytium. Is present there. What type of junctional complexes are present in the intercalated disc? We do have zona adherens. We do have gap junctions, and we do have desmosomes. These are three main, you know, junctional complexes which are present over there. Out of which, out of which, gap junction is the one which allows the movement of action potential from one cell to another, and that's why it is, it is the reason that it becomes a functional syncytium, guys. Obviously, when you give a, when the stimulus goes into the cardiac muscle, it can travel from one, one muscle to another, one fiber to another, that is because of this gap junction. Desmosomes, desmosomes are the ones which are anchoring structures. These are anchoring filaments which are holding these muscle fibers to each other here. So, the question here is that what type of junctional complexes are present in between the, in the intercalated disc? So, we have this adherent junction, we can call it zona adherens, gap junction, and desmosome. And desmosome are present there, right? And gap junction is the one because of which this intercalated disc is called as a functional syncytium. It's a functional syncytium. Okay.

Moit, my dear, I cannot increase the audio because my mic audio is full already, and I think if I go beyond this point, it just will start making some noise. Maybe the audio issues are on your side because if other people were having this audio issue, they certainly would have told me. Okay. Now, look at this picture, guys. This is a slide of a skeletal muscle. First of all, why it is a skeletal muscle? Can you see the branching? These, these, these fibers are not branched. They're parallel bundles, unbranched. They're like individual bundles are there. Secondly, look at the nuclei. How are the nuclei? They're flat and they're peripheral. We have flat and peripheral nuclei present over there. Multiple nuclei, flat and peripheral nuclei present there, and there are striations present inside them. Now, these striations, the cross striations, is a, is a very important feature of that. In fact, they have asked this question on the cross striations of the skeletal muscle. It's more of a physiology question, actually, but they've asked this question on the cross striations, like, image like this here. I'm, I'm very sure that you read about this image in your, in your physiology class in much detail. Now, I, I hope you know that these lines over there are called as, these are the called as Z lines, and from one Z line to another Z line, that is one sarcomere. You're looking at here, the functional unit of the cell, that is sarcomere, that is between the two Z lines here. What is this band over there? This, this, this central line over there is the M line or M band. M line. And this area is the A band, the anisotropic band or A band. And what is the A band basically? A band is nothing but it's the length of the myosin filament. The myosin filament is the I band is the unoverlapped, unoverlapped part. The portion of the actin filament which is not overlapped by the myosin filament, that is called as the I band. An unoverlapped part of the myosin filament is called as what? It is called as the H zone. The question here is Z line, M line, A band, H zone. They are like the way they are, they will be like this only here. What will change in length during contraction? That is the I band and H zone. Obviously, when the muscle contraction will take place, this overlapping will be there more. So, A band will get shortened, and H zone will also get shortened because in the contraction, these bands will get shortened here. So, the, the length of which of these bands and lines will get altered? So, it is the I band and H zone which would get altered during the contraction. If I, if I remember correctly, physiology, this was the question asked. So, that's a fun picture of a skeletal muscle, right?

Okay. Okay. Moving on, guys. Let's now move on to our next topic after, after embryology. That was a major part of the embryology that we discussed here. And again, whatever you've read, everything is important in the class, in the, in the regular class lecture or anywhere you attended the class. These are the topics that you have to focus on. Like, right now, if you look at myself and, um, how many days I'm just, if, in case, supposed to happen on the date given, so this is something that you have to read. This is something you just cannot leave them. And in the four, five hours of an actual discussion, my recommendation goes with these topics here. So, look, guys, let's get started. Now, in the upper limb, first, I'm going to start with few muscles because these are the muscles which again are asked in the recent time. Look at the muscles which are stretching from the vertebral column to the scapula, and then we have muscles from the scapula to the humerus also. I hope you can appreciate the muscle coming from the upper part of the cervical vertebrae, from the transverse process to the medial border of the scapula, that is levator scapulae. And the two muscles which are also coming from the, from the, this upper thoracic vertebrae, that is the rhomboid minor and rhomboid major. Rhomboid major was one of the questions asked in the recent time. Levator scapulae, guys, the name says, levator scapulae is a muscle which is responsible for the elevation of the scapula. And rhomboid minor and major, they retract the scapula. They not only retract the scapula, they slightly elevate the scapula also because look at the muscle fibers are obliquely present. So, they retract and elevate, retract and elevate. Rhomboid minor and rhomboid major. First of all, these muscles are supplied by the dorsal scapular nerve. Now, dorsal scapular nerve will be running like this. It is running like this in this region. And this dorsal scapular nerve, which is coming from the roots of the brachial plexus, it is going to supply all the three muscles here. Rhomboid minor and rhomboid major muscles, guys, these two rhomboids, they retract the scapula, I told you, and they also elevate the scapula, and they rotate the glenoid cavity downward. And that was a question asked in the exam. That what is the effect of the rhomboid major muscle on the glenoid cavity? Imagine if this is a glenoid cavity, let's say this, if this my wallet here is a glenoid cavity, and here is the scapula, I'm sorry. And if this is the glenoid cavity here, facing toward the lateral, right? So, when the scapula is retracted above and medially, my scapula will rotate like this. That means that my glenoid fossa, the glenoid fossa, is going to turn downward. Every time you elevate the scapula, medial border, and retract it, your glenoid fossa will turn downward. Rotation of the glenoid fossa upward is done by the serratus anterior muscle. That is for the overhead abduction. Rotating the glenoid fossa downward is done by the rhomboid minor and rhomboid major muscles, which are retracting the scapula. That was one of the questions asked.

Okay. Okay. Now, humeral fractures and nerve injuries, guys. Now, this is again a question. I have to focus on the areas from where questions are being asked here because these topics, guys, I mean, the people who attended the class with me, they know that we discussed these topics for six long days from morning to evening. And now we are just doing it all in four, five hours of time. So, obviously, we have to kind of only focus on the important part here, guys. Humeral fractures and nerve injuries. Now, what are the major sites of humeral fractures and what nerve will get involved in this? If there is a fracture at the surgical neck of the humerus, surgical neck of the humerus involvement, what nerve will get affected? Axillary nerve will get affected here. We know axillary nerve winds behind the surgical neck of the humerus, and that's why it is affected in the, the, the surgical neck of the humerus fracture. Mid-shaft fracture, which nerve? Radial nerve, because the spiral groove is giving passage to the radial nerve. So, mid-shaft fracture, most commonly, nerve involved is the radial nerve. SN, mid-shaft fracture, radial is the only nerve getting involved. You can have involvement of median nerve also, musculocutaneous nerve also, but usually it's the radial nerve because it's closest to the bone in the spiral groove. Then, supracondylar fracture. The nerve which is most commonly affected in the supracondylar fracture is the nerve which is not even present over there. I mean, it is going to separate in the forearm only, and that is the anterior interosseous nerve. I'm sure this question is asked in the ortho as well earlier. So, it's median nerve, but more precisely, it's the anterior interosseous nerve which is involved in the supracondylar fracture. Medial epicondyle fracture, it's the, it's the ulnar nerve, guys. Ulnar nerve involvement in the medial epicondyle fracture. And even if it is a lateral epicondyle fracture, the most commonly involved nerve is still the ulnar nerve because of what? Tardy ulnar palsy. It's a, you know, the tardy ulnar palsy, guys. What is going to happen? There is a, there is a cubitus deformity. If there's a fracture of the lateral epicondyle, this angle will increase. And if the angle will increase, like, increase from the medial side, if this angle will increase between the humerus and the forearm bones, then there's a stretch on the medial side, and that again causes the ulnar palsy. So, tardy ulnar palsy, be it medial epicondylar or lateral epicondylar fracture, the most commonly affected nerve is the ulnar nerve in both cases.

Okay. Okay. Moving on. Now, in the muscles of the upper limb, you cannot ignore the hand, guys. I mean, with the, again, the people who attended the class with me, you know that how much detail of the hand we've discussed about the spaces and the muscles and, you know, different nerves and everything about the hand is important to you. Now, first thing, when you look at the picture here, a question, obviously, they can cut down few muscles and they can show it to you. Like, I, I again, very firmly believe that if they want to give you an image to identify the muscles in the hand, they most probably, if they're asking the thenar, hypothenar, lumbrical muscles, they will give you an image like this. If they want to ask you interossei, that's a different story. But if they want to ask you thenar, hypothenar, lumbricals, this will be the picture. This kind, this will be the kind of image that you'll get. So, first, understand, if you see a muscle present in the thenar region, more on the outer aspect here, that is abductor. And if the muscle is more on the inner aspect, that is flexor. Abductor pollicis brevis, flexor pollicis because we have the longus in the forearm also. So, it's abductor pollicis brevis and flexor pollicis brevis. Opponens pollicis. Pollicis is a muscle which is attached to the first metacarpal. It is placed very deeply inside, so we will not be able to see the opponens pollicis muscle. Opponens pollicis, it will be like present deep to these two muscles, somewhere in between the two. So, I cannot see opponens pollicis in this image. The another muscle, the, the main muscle that they will ask you on this, or they usually ask us, is the adductor pollicis. A big triangular muscle. And to see the entire adductor pollicis muscle, I need to remove these tendons. Once I remove these tendons, then I will be able to see the adductor pollicis muscle more. And you see this big muscle which is coming from the mainly from the shaft of the third metacarpal there. Look at this big triangular muscle, that is adductor pollicis. A muscle, a very important muscle for gripping, because the one which brings the thumb inside. And this adductor pollicis is the muscle which is supplied by. You can go with the color code, guys. Red is for the nerve, and blue is for the median nerve. So, this is one thenar muscle which is supplied by the ulnar nerve. And that's why, uh, the test which is done for it, Froment's test, guys. You ask someone to hold any object between the, between the, between the index finger and the thumb. So, obviously, you'll be holding it like this. Let's, for example, if I once again take this wallet here. If I, if a person is pulling this wallet from the other side, my adductor pollicis is strong enough not to allow this wallet to leave the hand. But if my adductor pollicis is not working, what will I do? I will do a trick movement. I will curl the thumb like this to hold this wallet in my hand. And that is done by the other muscle called as flexor pollicis longus muscle. And this sign, when you curl your thumb to hold the object, is called as Froment's sign. Yeah, that is the thumb, the bending of the thumb will be seen there, and the test is called as Froment's sign. Ulnar nerve, I'm sure you all know about this test called as Froment's sign. Yeah. Okay. On the other hand, same story, guys. If the muscle is more outside, that is abductor. If the muscle is more inside, it is flexor. Abductor, flexor, opponens again, because opponens is a deeply placed muscle, right? So, out of the thenar and hypothenar muscles, these are the five muscles you are like usually you can get as a question, but nothing can beat adductor pollicis. That's the most important muscle to be identified in the NEET PG image-based question.

Okay. Moving on. Now, what about the lumbricals? Same picture, guys. It's the same image that you saw last. Lumbricals. Now, sometimes people say we are confused between the lumbricals and interossei. I'm like, no, there is no confusion between lumbricals and interossei. If you're looking at lumbricals, you must be looking at tendons. Can you see tendons over there? Look at the tendons. Tendons. Tendons. Tendons. Tendons are visible. So, the muscles which are taking their origin from tendons are lumbricals. Interossei are taking origin from bone. So, how will you see tendons over there? The tendons of flexor digitorum profundus, FDP tendons, flexor digitorum profundus tendon is giving origin to the lumbrical muscles. And L for lumbrical, and L for lateral. Every lumbrical is going from the lateral side of the corresponding finger. Guys, look at this. First lumbrical, second lumbrical, third lumbrical, fourth lumbrical. They will reach the finger. They'll reach their corresponding finger from their lateral side. L for lumbrical, L for lateral side. Lateral sides, right? That's the four lumbricals we have. Out of which, first and second lumbricals, which are actually unipennate, also maybe in the NEET PG image, you will not be able to appreciate unipennate, but the first and second lumbricals are unipennate, and they are supplied by the median nerve. Third and fourth lumbricals are bipennate. As I said, you may not be able to appreciate the pennation in the NEET PG image, but third and fourth lumbricals are bipennate, and they are supplied by the ulnar nerve. So, two lumbricals are by the median nerve, of the lateral two, which for the index finger and the middle finger lumbricals, that is the median nerve. And for the ring finger and little finger, these lumbricals are supplied by the, by the nerve. That's the lumbricals there.

Okay. Okay. I don't think that it is stuck at all from, from my end, because, you know, my internet speed is almost 1,000 Mbps right now. So, there's no chance that it is stuck from my side. Okay. Coming to the interossei, guys. Palmar interossei and dorsal interossei. Now, what you see in the palmar and dorsal interossei, we all know this mnemonic of PAD and DAB. Now, palmar interossei, PAD, that is palmar interossei for adduction. And dorsal interossei is for abduction. First, take the principal digit, guys. Principal digit is the middle finger here. The middle finger coming close to the middle finger is adduction, and going away is abduction. So, palmar interossei are doing this adduction. So, that means all the fingers will be having palmar interossei except the middle finger. Middle finger moving in the adduction of the fingers, the other fingers need to come toward the middle. So, palmar interossei is absent on the middle finger. That is one point they ask you. Unipennate, they are all unipennate in nature, and the middle finger is devoid of, there is no palmar interossei on the middle finger. And the test which is done to check the integrity of palmar interossei, that is called as what test? That is called as the card test, guys. That is called as the card test. Right. Interossei. This pin in it may be present or may not be present. We already have a muscle called as adductor pollicis. We have such a, such a main adductor of the thumb is already present. We discussed that earlier. So, thumb palmar interossei, it may be absent, usually, but thumb palmar interossei, the first pushia, it could be absent as well. No surprises there. Dorsal interossei, again, for number. All dorsal interossei are bipennate, and the job of dorsal interossei is abduction. Now, the point is, guys, we already have strong abductors for the thumb and little finger. That's why there is no dorsal interossei for the thumb, and there is no dorsal interossei for the little finger. But the middle finger, which was not having the palmar interossei, look at that. Middle finger is not having palmar interossei, is having double dorsal interossei. So, middle finger movement, whether it is toward the lateral side or middle side, it is done by the dorsal interossei only. So, no palmar interossei on the middle finger, but dorsal interossei. We have second and third dorsal interossei present on the, the middle finger. And the test which is done to check the integrity of the dorsal interossei, it is called as the Egawa test, guys. The test is called as Egawa test. You can see how it is done. A patient is asked to place the hand on a plain surface and ask him to move the middle finger because the middle finger movement is not done by palmar interossei. There is no palmar interossei on the middle finger. So, if you're moving the middle finger, whether it is toward the lateral side or middle side, it is done by dorsal interossei only. That's why the Egawa test is specifically for the dorsal interossei here. Card test for the palmar interossei, and Egawa test is for the dorsal. Yeah, correct. Absolutely perfect.

Clavipectoral fascia, guys. Another question, another topic from where the question is asked in the previous exam. Clavipectoral fascia, a fascia which is extending from clavicle to the pectoral muscle. Now, the fascia which is going to enclose two muscles. One is the subclavius muscle. A very small muscle which is present somewhere here in that region, just below the clavicle. And the other muscle is here, that is the pectoralis minor. That is called as the clavipectoral fascia. This muscle, subclavius, there, look at the pointer, guys. And this muscle coming from the third, fourth, and fifth rib is the pectoralis minor muscle. In the recent time, last year, in fact, again, there was a question asked. They showed the nerve piercing the pectoralis minor muscle and coming out, and that nerve was the medial pectoral nerve. But tell you why people got it wrong. The people got it wrong because when they saw the nerve piercing the pectoralis minor muscle and coming out, they compared this nerve with the nerve above. The nerve that you see, guys, above here, this nerve here, this nerve, look medial, and that looks like more lateral. That's why they got it wrong. Medial pectoral nerve and lateral pectoral nerve is not about which one is lateral, which is medial. It is about which cord of the brachial plexus are coming from. Lateral pectoral nerve is coming from the lateral cord of the brachial plexus. Medial pectoral nerve is coming from the medial cord of the brachial plexus. So, keep it simple. If you see a nerve piercing the pectoralis minor muscle, minor piercing, piercing pectoralis minor, then it is what nerve? It's the medial pectoral nerve. It's the medial pectoral nerve. But if you see the nerve piercing the fascia present above the pectoralis minor, the clavipectoral fascia is pierced by four structures. Lateral pectoral nerve is one of them. So, we have one vein, one artery, one nerve, one lymphatic. Cephalic vein is the vein which is piercing the clavipectoral fascia. That is cephalic vein. Lateral pectoral nerve. You can see the nerve over the lateral pectoral. We have the thoracoacromial artery. This vein is cephalic vein, and we do also have some lymphatics as well, guys. There are some lymphatics which are draining into the apical lymph node. They're also going to pierce the clavipectoral fascia. That also is a question asked in the exam here. That what structures are pierced in the clavipectoral fascia? One vein, one artery, one nerve, one lymphatic. Cephalic vein, thoracoacromial artery, lateral pectoral nerve, lateral pectoral nerve. And then we have lymphatics which are also piercing it. Okay. What is the extension of the clavipectoral fascia? After covering the pectoralis minor muscle, the extension of the clavipectoral fascia below is called as the suspensory ligament of the axilla. Guys, look at that. That region over there. This area here is the suspensory ligament of the axilla. That is the one which is basically keeping this floor of the axilla slightly elevated, slightly dome-shaped. Your floor of the axilla is not flat. It is slightly dome-shaped, and that is because of the suspensory ligament of the axilla.

Okay. Now, transverse section of the axilla. Talking about this region only. Now, if you take a transverse section of the axilla, how this section is going to look like? The transverse, TS of the axilla is going to look like something like this. Here, this is again a question asked in the exam. When you take a TS, TS of the axilla, laterally, you will see the humerus bone. So, that's the humerus bone over there. You can see medially, I will see the rib cage. That is the rib cage that you're looking at here. Anteriorly, I have pectoral muscles. That is pectoralis major and minor is there. Look at the two muscles over there. That is pectoralis major and minor. That is anterior. Major and minor is the muscle which is going to cover the scapula. That is subscapularis. And the muscle which is going to cover the rib cage is serratus anterior. So, that muscle is subscapularis. It is in front of the scapula. And the muscle which is covering the rib cage is serratus anterior. And, guys, this is serratus anterior. Then the nerve which is supplying serratus anterior is the long thoracic nerve also. Long thoracic. What is there inside? Now, inside the axilla, I can see that is the axillary sheath. That white color, sleeve-like structure that you see, that is axillary sheath. Axillary sheath. Can you see the axillary artery there? Axillary vessels are there. And around the axillary artery, I have cords of the brachial plexus. Now, obviously, this is toward the lateral side. That's the lateral cord of the brachial plexus. That's the medial cord of the brachial plexus. That's the posterior cord of the brachial plexus. Posterior cord of the brachial plexus gives origin to many nerves. One of them is the subscapular nerve. Upper subscapular and lower subscapular nerve. And they are going to supply the subscapularis muscle, guys. There is subscapular nerve is there. Upper subscapular, lower subscapular. Upper and lower, but subscapular nerve here. And then we have the lateral cord and the medial cord of the brachial plexus to be seen. If I remember correctly, in the INICT, back when it was asked, they asked this question on the transverse section of the axilla, and they asked three structures in this. I'll tell you what three structures were there. They asked the medial cord of the brachial plexus, they asked the long thoracic nerve, and the subscapularis. These were three structures specifically marked in that picture, and they asked to identify them here. One was the medial cord of the brachial plexus, long thoracic nerve, and subscapularis muscle. I remember that correctly.

Okay. Coming to the brachial plexus. Now, again, whatever we read in brachial plexus about branches and everything, that is fine. But from the core, purely from the exam point of view, what is important from the image-based point of view, guys? Brachial plexus is formed by the ventral primary rami of C5 to T1. You know, C5, C6, C7, C8, and T1. Once the C5 and C6 roots will join, C7 is there. C8, T1 will join. They will form the roots will join to form what? Trunks. So, we have upper trunk, middle trunk, and lower trunk. After the trunks, these, you can see these trunks are giving contribution to each other. As you can see, the upper trunk is giving a contribution to the middle. Middle is giving a contribution to the lower. Lower is giving contribution to the middle, and middle is giving contribution back to the upper. This area of the brachial plexus is called as the divisions of the brachial plexus. And divisions are one part of the brachial plexus branches. There are no nerves coming out from there. And that also is one of the INICT question that which portion of the brachial plexus does not give any branches? Like, there are nerves coming out from the roots, from the trunks, from the cords, but not from the divisions. There are no branches from the division part here. And then finally, we have the cords of the brachial plexus. As we just discussed, the cords of the brachial plexus are named based on the relation to the axillary artery. Lateral to the axillary artery, we have the lateral cord. Posterior to the axillary artery, posterior cord. Medial to the axillary artery, medial cord. Now, I can assure you that in the exam, guys, they're not going to ask you every single branch from the cord of the brachial plexus. It's not an easy thing because every brachial plexus might look a little.

different. They may not ask you the branches coming from bra chords or brachial plexus. But they can ask you the continuation of the chord like lateral cord continuation.

Lateral cord continuation, guys, this is a continuation. Lateral cord. That's a continuation of posterior cord. That's a continuation of the medial cord. Here, the continuation of the lateral cord is in the form of musculocutaneous nerve. The continuation of the posterior cord is in the form of radial nerve. And the continuation of the medial cord is in the form of the ulnar nerve. The long nerves which are going into the upper limb. So musculocutaneous is lateral cord continuation. Radial nerve is a continuation of the posterior cord. And ulnar nerve is a continuation of medial cord or brachial plexus. And median nerve is something which is coming from both lateral as well as medial cord of brachial plexus. That's the median nerve. Median nerve is one major nerve of the upper limb. It is coming from lateral cord also and it is coming from medial cord of the brachial plexus. Okay. So at least make sure that you identify these, these continuations of the cords of the brachial plexus there.

Now, in the brachial plexus, the two major injuries, guys, I'm sure you read about these injuries in the ortho as well. That is the injury to the lower trunk of the brachial plexus, that is called as Klumpke's palsy. And the injury to the upper trunk of the brachial plexus, that is called as Erb's palsy.

Now, first let's talk about Klumpke's palsy. If the injury to the lower trunk is there, to the Klumpke's palsy, that means the root values which are affected are which one? That is C8 and T1. Lower trunk, C8 and T1. C8 and T1. C8 and T1 injury, it is going to affect those nerves which are supplying the intrinsic muscles of hand. If the C8 and T1 is injured, guys, that means your intrinsic muscles of hand will get affected and involvement of all the intrinsic muscles, lumbricals and interossei will get affected. The person will get a claw hand. There's a hyperextension at the MCP joint and flexion at the interphalangeal joint. There will be claw hand in case of the Klumpke's palsy and it's a complete claw hand. Claw hand, claw hand will be there. But because of the injury to the T1 also, it's a C8 and T1 injury. Injury to T1 can also cause Horner's syndrome also. So the patient with Klumpke's palsy, they may have Horner's syndrome also.

But Horner's syndrome be similarly, if the injury to the upper trunk of the brachial plexus, the injury to the upper trunk of the brachial plexus is called as Erb's palsy. In Erb's palsy, the root values which are affected is the C5 and C6. C5 and C6 is the root value. In many nerves, but if I talk about some particular muscles which are supplied by C5 and C6 via axillary nerve and musculocutaneous nerve, so it is deltoid and it's the biceps and brachialis muscle. Coracobrachialis, guys, coracobrachialis is supplied by C7. So coracobrachialis is spared. Mainly the deltoid muscle and biceps muscle is affected. Mainly or muscle. But just think about two muscles only. If deltoid is not working, you are not able to abduct. So shoulder is adducted. So we have an adducted shoulder. Biceps is not working, so elbow is extended and it is also pronated because biceps is a very strong supinator also. So we have an extended elbow and the pronated forearm as well. Adducted shoulder, extended elbow, pronated forearm. I'm sure we are talking about what? Policeman's tip hand or the policeman's tip deformity. And the policeman's tip deformity is a feature of the Erb's palsy here. So generally, in exam questions, they will ask you about Klumpke's palsy, which root values are affected, which trunk of brachial plexus is affected here. Similarly, Erb's palsy, which root value will be spared? Like which root value is spared? The C7 root value is spared. And C7 supplies which muscle? That is coracobrachialis muscle. That's why out of the three muscles present in the anterior compartment of the arm, biceps and brachialis are affected, but coracobrachialis is spared because C7 is supplying the coracobrachialis muscle. Okay.

Sir, moving on, going to the three major nerve end injuries, talking about the upper limb, how can we leave on the nerve injuries, guys? Nerve injuries is the most important thing in the upper limb here. Now, radial nerve, which we just saw, it is coming from the posterior cord of brachial plexus, coming from C5, C6, C7, C8, and T1. What's the course of radial nerve? Radial nerve starting from axilla, it goes behind the humerus into the spiral groove, as you can see, comes in front of the lateral epicondyle and divides in front of the lateral epicondyle into a superficial branch and the posterior interosseous nerve. Into the posterior interosseous nerve, that's the radial nerve course.

I take now, in the axilla, the radial nerve supplies the triceps muscle. That's one thing. It again supplies triceps muscle into the spiral groove or the radial groove. Then it supplies another important muscle called as ECRL, extensor carpi radialis longus. And what makes ECRL so important muscle? It is one of the wrist extensors. That's why it is important. It's one of the wrist extensors. It is supplied above the lateral epicondyle only, that is wrist extensor ECRL. And then we have posterior interosseous nerve, which is supplying remaining all extensors. Remaining extensors, they are all supplied by the posterior interosseous nerve. When I say extensor digitorum, extensor carpi ulnaris, extensor digiti minimi, extensor indices, extensors, all other extensors are supplied by posterior interosseous nerve. Just one ECRL, extensor carpi radialis longus, supplied by the radial nerve above the lateral epicondyle. Rest are by the posterior interosseous nerve. The superficial branch is a cutaneous nerve. It just supplies the skin on the dorsum of hand, lateral three and a half.

What about the radial injuries? Radial nerve can get injured in the axilla. I'm sure you all know that, that is called as a crutch palsy. Radial nerve get injured into the spiral groove, that is a Saturday night palsy. Radial nerve can get injured in front of the lateral epicondyle, and there could be direct injury to posterior interosseous nerve also, very close to the head of the radius. So that is posterior interosseous injury can also be there.

The fourth common feature, guys, if the radial nerve is injured in the axilla, here, right here, all the extensors are gone. Triceps is not working. Wrist extensors not working. So the position of the patient will be flexed elbow, wrist is dropped, fingers are also dropped, and sensory loss is there. So in the crutch palsy, elbow will be flexed, wrist will be flexed, fingers will be flexed, or sensory loss will be there. All the joints are flexed. So we have flexed elbow, wrist drop, finger drop, sensory loss.

If the injury is in the spiral groove, the second one, guys, in the spiral groove, that is a Saturday night palsy. It is Saturday night here. In Calgary today, uh, tonight, it's, I mean, Saturday night right now, after Sunday morning. So this is in the Saturday night palsy. In Saturday night palsy, guys, what happens is that triceps is partly spared. I mean, triceps is partly working. So patient is having difficulty in elbow extension. Difficulty, difficulty in elbow extension, and rest everything is same. Wrist drop, finger drop, everything is same. Only thing is, in this case, it was a flexed elbow. Here we have weakness in elbow extension.

If the injury is in front of lateral epicondyle, first of all, triceps is working perfectly all right. No problem. Another important thing, ECRL. If ECRL is spared, the patient will not have wrist drop because ECRL is a, what? Wrist extensor. That's why there is no wrist drop. Finger drop will be there. Finger drop will be there. Sensory loss will be there, but wrist drop will not be there because ECRL is spared at the lateral epicondyle case. ECRL is spared. And if the injury is to the posterior interosseous directly, again, we have what? We have a finger drop. But this time, there is no sensory loss because the superficial branch is also spared. Superficial branch is also spared. So patient is only having a finger drop in that case. So based on the symptoms of the patient, you can make out that possibly the location of the injury. Flexed elbow, wrist drop, finger drop, sensory loss, axillary injury. Saturday night palsy, weakness of elbow extension, wrist drop, finger drop, sensory loss. Lateral epicondylar injury, where is only finger drop and sensory loss. Posterior interosseous injury, there is only finger drop. There is no sensory loss in that case. Right? So that is about the radial nerve injury.

What about median nerve? Now, median nerve and ulnar nerve, one good thing is that these nerves are not supplying anything in the axilla or arm. The first muscle supplied by median nerve is after the elbow. So, guys, look at the median nerve over there. That's the median nerve which is going into the cubital fossa and from the cubital fossa, it runs between the forearm muscles and then passes deep to the flexor retinaculum. That green band over there is the flexor retinaculum. Let me start with the terminal part. Once the median nerve reaches the hand, it is going to supply the thenar muscles. Remember all thenar muscles except adductor pollicis. Adductor pollicis was supplied by the ulnar nerve. So all thenar muscles except adductor pollicis. And it also supplies the first two lumbricals. Unipennate lumbricals, L1 and L2. The unipennate lumbricals are also supplied by this. Just before, just before the median nerve goes deep to the flexor retinaculum, it gives off a branch which is passing superficial to flexor retinaculum, and that is called as a palmar cutaneous branch. Guys, palmar cutaneous branch is the one which is going to supply the skin of the palm of the palm, not the fingers. Palm skin supply. And why it is important? Because if the patient comes to you with a carpal tunnel syndrome, then thenars will be gone, lumbricals will be gone, but this nerve will be working because the nerve is above the flexor retinaculum. And that's why in carpal tunnel syndrome, the patients, they do not have sensory loss on the hand, on the palm. They only have sensory loss on the fingers. Palm any fingers? Sensory loss in carpal tunnel syndrome, we'll see that.

In the forearm, median nerve, it gives off a branch called as anterior interosseous nerve. It's a deep nerve, called as anterior interosseous nerve. Main median nerve supplies the superficial flexors like flexor digitorum superficialis, flexor carpi radialis. Other muscles. FDS is important. Remember that flexor digitorum superficialis. Anterior interosseous nerve, which is a deep nerve, it supplies the deeper muscles like flexor digitorum profundus, lateral half. Lateral half of flexor digitorum profundus and flexor pollicis longus. And what makes these two muscles important? Flexor digitorum profundus muscle, it reaches the distal phalanx. Flexor pollicis longus also reaches the distal phalanx. They are the only muscles on the flexor side, distal phalanx. That is flexor digitorum profundus and flexor pollicis longus. They're reaching the distal phalanx. Flex if you want to flex the distal phalanx, I need this nerve. I need this anterior interosseous nerve, otherwise you cannot flex the distal phalanx.

Median nerve injury, higher injury at the elbow or above the elbow. Lower injury at the wrist, wherever, like close to carpal tunnel syndrome, or there could be an isolated injury to the anterior interosseous nerve. Guys, anterior interosseous nerve injury also. Anterior interosseous nerve injury. If it is a higher injury or lower injury, let's go with these two, guys. If there's a higher injury or lower injury of the median nerve, they have ape thumb deformity because thenars will get affected. The patient definitely will have a thumb deformity. But if a patient is having a higher injury, that means his FDS and the lateral half of FDP is also not working. And that's why he's not able to flex the index finger, especially. But in most of the cases, middle finger flex. So when you ask the patient to make a fist, ape thumb deformity is there. When you ask the patient to make a fist, so he will have a pointing index finger or maybe hand of benediction, like this, that is while making a fist. So ape deformity is there for sure. But hand of benediction or pointing index finger will be there while making fist. That is important. Patient normal while making fist. Fist, you will see the pointing index finger or hand of benediction. That is because of higher injury because FDS is not working, lateral half of FDP is also not working. If it is a lower injury, then obviously FDS is working, FDP is working. So in this case, you will have a thumb deformity. No problem in making the fist. Patient can make a fist. But I told you, if the injury is at this point, which nerve will be spared? The palmar cutaneous branch will be spared. And if palmar cutaneous branch is spared, that means the sensory loss will be seen only on fingers, but not in the palm. Ape thumb deformity, but there is no sensory loss on the palm. That is the case of lower injury or the carpal tunnel syndrome.

If there is an injury to anterior interosseous nerve, just imagine the main median nerve is working. Median nerve is working fine. But the anterior interosseous nerve is affected. Guys, if anterior interosseous nerve is affected, that means you're not able to flex the distal phalanx of this index finger. You're not able to flex the distal phalanx of the thumb. And that's why you're not able to make an "okay" sign like this. You cannot make a circular "okay" sign like this. You'll make a flat "okay" like something like this. Look at this on this one side, you can make a circular "okay". That is a normal "okay" because the distal phalanx can flex. But in this case, the distal phalanx is not able to flex. That's why the patient will make an "okay" sign like a flat "okay" sign here, which is an indication of anterior interosseous nerve injury here. So it's a higher injury, lower injury. And then we have, if there is injury to only anterior interosseous nerve, then you see a patient who's having a positive "okay" sign.

Anterior interosseous nerve supplies FDP and FPL, sir? Yes, it does. It does FDP lateral half, FPL, even pronator quadratus also, not very important, so I did not mention here.

Coming to the ulnar nerve, guys, the last one. All nerve, as we know, the root value for the ulnar nerve is C7, C8, and T1. Heavily C8 and T1 because we need to supply the muscles of hand. Ulnar nerve, it passes behind the medial epicondyle, where it is very vulnerable to injury also. Ulnar nerve is basically passing through a canal which is present here, that is called as a cubital tunnel. It is made by flexor carpi ulnaris muscle. Close to the elbow, there is sorry, yeah, look at that. That's a flexor carpi ulnaris muscle and flexor carpi ulnaris muscle gives a passage to this nerve. That is called as a cubital tunnel. So ulnar nerve can also get injured in the cubital tunnel, called as a cubital tunnel syndrome. Then this nerve in the forearm, what you'll see, it is going to supply, it is also going through a canal which is like from called as a Guyon's canal, present deep to the pisohamate ligament. So if it is a higher injury of the ulnar nerve, generally it could be because of medial epicondyle fracture. It could be because of the cubital tunnel syndrome. Or if it is a lower injury of the ulnar nerve, that is Guyon's canal syndrome. Ulnar nerve can get compressed in the Guyon's canal. Ulnar nerve in the forearm, it is just supplying one and a half muscles. One and a half, guys, when I say one and a half, one is what? One is this only nerve. One is a flexor carpi ulnaris. And half of which one? Flexor digitorum profundus, medial half of flexor digitorum profundus. When the nerve passes through Guyon's canal, then the majority of the intrinsic muscles of hand are the ulnar nerve supplied. Like first of all, it supplies all hypothenar muscles. After that, it supplies all interossei. It supplies lumbricals also, bipennate lumbricals, which one, third and fourth lumbricals also. And it is finally going to supply the abductor pollicis muscle as well. The abductor pollicis muscle is also called as a graveyard of all nerves. This abductor pollicis muscle is also called as a graveyard of nerves.

Now, whether it is the ulnar nerve injury at the higher level or the lower level, claw hand, to obviously intrinsic muscles are involved, so there will be claw hand. The only thing is, if it is a lower injury, if the patient is having a lower injury, the claw hand will be more prominent. If it is a higher injury, the claw hand will be less prominent. And I'm sure you all know that is called as paradoxical ulnar paradox. Ult paradox is because of which muscle? That is because of flexor digitorum profundus. In the lower injury, if the patient is having an ulnar injury in the lower part, and imagine FDP is working, that FDP muscle will cause more flexion at this distal interphalangeal joint. And that's why it looks like a more severe claw hand here. So lower injury is not a severe claw hand. Higher injury may we have a less severe claw hand, and that is called as ulnar paradox. That is the paradoxical situation called as paradox. Yes. Perfect. Yes, guys, FDP is by two nerves here. Neil, FDP is a hybrid muscle. It is supplied by two nerves.

So, few more questions on histology, guys. When I talk about histology, well, nothing is more important histology than the slides of some lymphoid organs. So you're looking at some lymphoid slide. What you're looking at right now, guys, this is a slide of a lymph node. Lymph node slide. And if it is a lymph node, how we're going to separate the lymph node from palatine tonsil, from spleen, and from thymus? In the first of all, in the lymph node, you can see there is a capsule over there, like on the top. That is a capsule. There that's a capsule region. And you can, you can divide the slide of lymph node into the cortex and medullary part. The cortex and medulla can be seen separate. These lymphatic nodules. I'm sure you can clearly make out the lymphatic nodule with germinal center. These lymphatic nodules and lymph nodes are present only in the cortex. Medulla only in the cortex. We have lymphatic nodules. Number one. Number two, capsule and trabeculae. You have a capsule and trabeculae. There is capsule over there and these the trabeculae. There is these extensions are called as trabeculae. And we have a space present deep to them. That space is called a sinus. Either you call it subcapsular sinus or that is called a trabecular sinus. Lymph, lymph node. The lymph basically goes into this region here. That sinus is called as a subcapsular or trabecular sinus, which is a very unique feature of the lymph node. You will not see the sinus like this in the spleen or in palatine tonsil. So subcapsular or trabecular sinus will be there. Trabeculae present there. As I said, lymphatic nodules are present only in the cortex. Medulla, we have the cords. Medullary cords are there and sinuses. And at the junction of the cortex and medulla, this is an area which is called as a paracortex. And paracortex is called as a thymus-dependent zone. Lymphatic nodule, guys, in the lymphatic nodule, we have mainly what? B lymphocytes. And this is the paracortex region where we have T lymphocytes here. That's a question asked. Pure question. But the question was asked that which part of the lymph node is thymus-dependent portion of the lymph node? Thymus-dependent portion, T lymphocytes. And T lymphocytes are present where? At the junction of the cortex and medulla, that is the paracortex. That is where we have the T lymphocytes. So that is a slide of a lymph node. Okay.

Okay. Now, if you look at this slide again, I can see lymphatic nodule. Again, I can see lymphatic nodule. Uh, I can, I can actually talk about these injuries and all that, but I, I'm trying to respect that whatever is done in ortho, if these things are done, why we want to do that the same thing from two different sources, right? That's why I have to refrain myself from discussing everything. Limited time, we have to discuss most of the topics. So obviously, we have to, I have to kind of cut down on the information which are not very important or either covered in other subjects here. So, so guys, once again, look at the lymphatic nodules. You can see lymphatic nodules. This time, apart from lymphatic nodule, you can see a big space over there, present over that. That's a palatine tonsil. That's a lymphatic nodule. That space over there is a tonsillar crypt. Tonsillar crypt and tonsillar cleft. You know that when you look at the oral surface of palatine tonsil, the spaces that we have in between them, that is called as a tonsillar crypt over there, right? The most important thing about the palatine tonsil would be that the oral surface of the palatine tonsil, especially crypts present, that is covered with the stratified squamous epithelium. Lymphatic nodule. And you are looking at the stratified squamous epithelium and some crypts are visible to you. It is going to be palatine tonsil. Simple.

Look at the next one. In this slide, what slide is this? See, again, I can see lymphatic nodule. Half lymphatic nodule, half lymphatic nodule. There is lymphatic nodule present everywhere. Right? Lymphatic nodule is there. I cannot see any crypt over there. I cannot see any stratified squamous epithelium. And because lymphatic nodules are dispersed everywhere, this is a slide of a spleen. Spleen specialty, guys, there is no differential cortex. There is no cortex medulla. You can see lymphatic nodule, and each of these lymphatic nodules are spreading everywhere. That's why there is no differential cortex and medulla. It is a slide of a spleen. If I zoom in on one, like more into this lymphatic nodule area where lymphatic nodules are present. The important feature of the spleen is that first of all, this lymphatic nodule area, this is called as the, in the spleen, that is called as the white pulp. White pulp, WBCs, white blood cells over there, that's why we have white pulp is there. We have lymphocytes present in that region, that is white pulp. Then we have a blood spread into the parenchyma. That's why it gives a red tinge color over there. That is that is called as a red pulp over there because RBCs are present. Important thing, spleen slide. In the slide of a spleen, you're going to identify that the lymphatic nodules are having blood vessels. Can you see arteries over there? Look at these arteries. Look at these arteries. Look at these arteries. Blood vessels, blood vessels inside the lymphatic nodule. Guys, blood vessels present inside, eccentrically placed blood vessels inside the lymphatic nodule is the feature of the spleen. Simple as that. If you're looking at a lymphatic nodule covered with a capsule, there is a subcapsular and trabecular sinus, and the lymphatic nodules are present only in the cortex, lymph node. If you look at the lymphatic nodules which are lined by the stratified squamous epithelium and there is a crypt also visible to you, crypt and now stratified epithelium is there. It is a slide of a spleen. It is a slide of a palatine tonsil. If you're looking at a slide where the lymphatic nodules are dispersed everywhere because there is no differentiated cortex and medulla, and there's an artery to be seen inside the lymphatic nodule, it is a slide of a spleen. Just work for the basics to identify the structures. So that is a spleen over there. Yeah. Non-keratinized. Yes, of course. Orality non-keratinized.

Now, again, you're looking at the lymphatic, lymphatic, lymphocytes are seen, but there is no lymphatic nodule here. It's a slide of a thymus. Now, in the slide of a thymus, what you're going to see that the entire thymus is divided into by by the septum. Can you see all the septa over there? Look at the septum. Look at the septum. Look at the septum. They're dividing the entire thymus into small, small lobules. And every lobule is having its cortex and medulla. The cortex, beha, but like there is no lymphatic nodule there. We do have lymphocytes. Now you can see cortex over there and you can see medulla also. But one thing is to be noted. These trabeculae are sending extensions inside. Can look at this. I'm just making a red color over there. Look at these extensions. And because of these extensions, your cortex is also divided inside. One lymphatic, inside one lobule, the trabeculae are going inside. And these trabeculae are dividing the cortex, but they're not reaching the medulla. So it's like all these cortex is sharing one common medulla inside. Generally, you can identify thymus like this also. If they let's say they give you a very good picture of an old thymus and let that be too little zoomed in, maybe at 40x or beyond 40x into the medullary part, you may also be able to appreciate something that is called as a Hassall's corpuscles or thymic corpuscles. What is Hassall's corpuscles? We have a hyaline mass in the center, and we do have some reticular epithelial cells which are surrounding them. Dying epithelial reticular cells are present around it. And that is called as Hassall's corpuscle, which is also the identifying feature of thymus. But again, if you ask me personally, I feel thymus is not that important from the histology point of view. It is most likely to be lymph node, palatine tonsil, and the spleen. But you know, you never know about the exam. But I'm just saying it's my, my brain says that thymus is probably not going to be asked because thymus can be confused with many other slides. Okay. Yes. Perfect. So guys, that is about the lymphatic, that is Hassall's corpuscle or thymic corpuscle present in the medulla.

So that was about the embryology part and the upper limb and some histology we have done. Um, let's continue. Break. Laying in beach, but not now. We will take a break after around like 45 minutes or so. Okay. Just, just give me one second, guys. Let me just open the window here. One second. If you hear some sound of cars going from here to there, just please excuse me. I have to open the window because to keep this room a little ventilated. Okay, let's go to the to the lower limb. Break. I will give you a break. I will give you a good 20 minutes break. Not this 5-minute break. I will give you a 20 minutes break in between. But not now. Let's continue, guys.

So in lower limb, first, guys, look at this picture. When you're looking at the posterior abdominal wall, there's a muscle that you're looking at that is called the psoas major muscle, coming from the lumbar vertebrae. Look at the arrow over there. Psoas major muscle. And there's a muscle coming from the iliac fossa called as iliacus. Now, psoas major and iliacus muscle, the two main muscles which are present on the abdominal wall. They're going to help you identify the nerves coming from the lumbar plexus. The poor lumbar plexus. Major feature present. Lumbar plexus is formed by the L1, L2, L3, L4, L5 nerves. And this entire lumbar plexus lies behind the psoas major muscle. So to identify the nerves of the lumbar plexus, you just have to see how the nerve is coming out. Is it piercing psoas major? Is it coming out lateral side to the psoas major? Medial to the psoas major? How exactly it is coming out? That's how we have to identify it. Okay.

Look again, the same picture. I mean, that kind of picture. I hope you can appreciate the two muscles, psoas major and iliacus. Now, first, look at the nerve which is piercing. If a nerve is piercing the psoas major muscle and running on it, that muscle is that nerve is genitofemoral. I'll talk more about these nerves individually also. Right now, just try to identify them. Genitofemoral nerve is piercing the psoas major. Psoas major and coming out. Look at the nerve which is coming out between psoas major and iliacus. That's how we define the course of this nerve also, femoral nerve. It emerges between the psoas and iliac muscle. Psoas iliacus. And look at the nerve which is present medial to psoas major, that is obturator nerve. So the nerve piercing psoas major muscle, genitofemoral. Lateral to psoas major is femoral. And medial to psoas major is obturator nerve here. Okay. Then you can also see another nerve which is also running within the iliac fossa, within iliacus muscle, within iliacus and then passing deep to the inguinal ligament, that is lateral cutaneous nerve of the thigh. Look at that lateral cutaneous nerve of the thigh. The compression of the nerve which causes meralgia paresthetica. That lateral cutaneous nerve of the thigh is running within the iliac muscle. That's how you got to identify them here. And then look at the nerve starting from above. We are looking at the nerve called as subcostal nerve. Not the part of lumbar plexus. That is T12 nerve. Subcostal nerve. And then we have the two nerves coming from L1 called as iliohypogastric and ilioinguinal nerve. In that sequence, first iliohypogastric and then we have ilioinguinal nerve. Iliohypogastric and ilioinguinal nerve. Okay, guys. Subcostal nerve, iliohypogastric nerve, ilioinguinal nerve, all these nerves that looking at. Oh, there are questions on the genitofemoral nerve and other nerves also. But what you can use this picture as well for is to understand or to remember couple of relations also. Be look at subcostal nerve, iliohypogastric and ilioinguinal on the other side. I want to look at the other side. These three nerves are forming the posterior relation of kidney. Nerve, kidney, posterior relation. And that's why these nerves are vulnerable to any surgical approach to the kidney. Obviously, you're going to approach the kidney surgically from the posterior side. So the three nerves in the posterior relation of kidney are T12, L1, L1. So subcostal, iliohypogastric, ilioinguinal nerve. The three nerves forming posterior relation of kidney.

Now look at the two nerves here, genitofemoral nerve, lateral cutaneous nerve, and femoral nerve. These three nerves, obviously on the right side, the left side may be on the right side, they are also forming the posterior relation of cecum or you can say cecal bed. They lie in relation to the cecum. They are posterior to cecum. Three nerves: genitofemoral, lateral cutaneous nerve of thigh, and femoral. Cecum. So they're vulnerable to injury in the cecal surgeries or when you approach the cecal or let's say the patient is having a retrocecal appendix. Then obviously you got to be careful with these nerves here. And then we got an obturator nerve. Obturator nerve is in close relation to ovary. It is forming the relation to the ovarian bed. The nerve forms the relation to the ovarian bed. It is in relation to the ovarian bed, very close to the ovary. And that's why in ovarian carcinoma, the obturator nerve can also be involved, and that can cause the weakness of adductor muscles. That can cause the sensory loss on the medial side of thigh. Pain can also be seen radiating on the medial side of thigh because of obturator. So when you're looking at the, I hope you can see that sound here. Some Saturday evenings, you know, some people do get their sports car out and just test their speed on the road. So you may hear all these sounds in between. So I'm sorry for that.

So guys, the what do you see? Subcostal, iliohypogastric, ilioinguinal, while another three nerves forming the posterior relation of kidney. Then we have genitofemoral nerve, lateral femoral nerve, forming the posterior relation of the cecum, obviously on the right side. And then obturator nerve is in close relation to ovary. Relations questions. Remember the lumbar plexus. If you see a nerve present like if if you think about the kidney, it is more logical for the examiner to ask you the posterior relation of kidney because surgical approach to the kidney is from posterior side. So posterior relation of kidney, retrocecal appendix is the most common position of appendix. So that's why knowing the cecal relation is important. Okay.

So guys, this is about the of the structures which are forming some posterior relation. Now, from this lumbar plexus, some of the, you know, nerves need to be discussed slightly more detail because the questions are being asked. And first question, I'm sure you must have discussed this question with Dr. Rajat in pathology or somewhere else also, that is a psoas abscess. Here, I just have to show you this picture because psoas major muscle is the one which originates from the transverse process of the upper four lumbar vertebrae. Look at on this side, you can see the abscess present along the muscle, that is a psoas abscess. And this question was asked in the recent time. It was a radiological question. The thing about the psoas abscess is it trickles along with the psoas major muscle and psoas fascia to the lesser trochanter. And because the psoas abscess can reach to the lesser trochanter, so it may give an appearance of an inguinal hernia also, right? It just may look like an inguinal hernia if you look at the psoas abscess when it kind of trickles down and reaches the lesser trochanter area. So that's just a picture to show that where the normal psoas major muscle and how the psoas abscess is going to look like on the posterior abdominal wall. Yeah, I know guys, I'm not that expert to tell you whether it's a Bugatti or it's a Ferrari, but whatever, like, okay.

Now look at this nerve, guys. The nerve which is piercing the psoas major muscle, uh, which is which is coming out, but look at the nerve when the when the genitofemoral, sorry, piercing the psoas major muscle, when you look at the nerve piercing the psoas major muscle, coming out, it is dividing into two branches. One of the branch is called as a femoral branch and one is a genital branch. The one which is more toward the lateral side, it's the femoral branch of genitofemoral. And the one which is more inside is a genital branch of genitofemoral nerve. Now, femoral branch of genitofemoral nerve, it pierces the skin and comes out, and it supplies the skin exactly over the femoral triangle. Look at that area, guys. The skin over the femoral triangle is supplied by the femoral branch of genitofemoral nerve. So that's why when we're testing the cremasteric reflex, when you scratch along the medial aspect of thigh, you stimulate this nerve only, that is the femoral branch of genitofemoral nerve. Whereas the genital branch of genitofemoral nerve, it is going to supply the muscle that is the cremasteric muscle, and that is forming the efferent of the cremasteric reflex. Question: If the genitofemoral nerve is the main nerve which is forming the afferent and efferent of what reflex? Cremasteric reflex. And secondly, because the femoral branch of genitofemoral nerve supplies the skin over the femoral triangle, to femoral vein cannulation, if you're like, you're putting a cannula on the femoral vein, you need to anesthetize surface anesthesia to which nerve? Femoral branch of genitofemoral nerve. So afferent and efferent of cremasteric reflex by the genitofemoral nerve. That's one question. And another question is that femoral branch of genitofemoral nerve is the one which is anesthetized in femoral vein cannulation. In femoral vein cannulation.

Look at this another nerve, guys. What nerve is that here? I, I'm just, I'm just like waiting for one second. I want you to tell me, guys, what nerve is this here? Just based on how it is coming out and running into the lower limb. Tell me what nerve is this. Come on, quickly. Yes. Perfect. Yeah, you all are well prepared already. That's the lateral cutaneous nerve of thigh, guys. Good answer, guys. That's the lateral cutaneous nerve of thigh. How do we identify the nerve? You can see the nerve obviously coming from posterior side of psoas major, running within the iliacus muscle, and then it is passing deep to the inguinal ligament. And while it is passing deep to the inguinal ligament, sometimes it is compressed deep to the inguinal ligament, and that causes the pain and the like sensory pain and burning sensation on the lateral side of the thigh. That is called as meralgia paresthetica. That is called as meralgia paresthetica. Right? That is also a question asked about it.

Now, genitofemoral question, surgery question, it was about trocar placement. I don't remember the language of the question correctly, but it was something about the trocar placement. Trocar and mesh was placed on in some of the surgery of the abdomen, and after that, while doing that, a nerve is compressed somewhere in the posterior abdominal wall, and the pain is radiating into the lower limb. Question: What is the catch here? If the question says the pain is radiating into the thigh, that means while putting the trocar, maybe the nerve compressed is a lateral cutaneous nerve of thigh. But if the pain is radiating into the leg, thigh, if the pain is radiating into the leg, that means femoral nerve is compressed, because femoral nerve will continue to form the saphenous nerve, which is supplying the medial side of the leg. So thigh, leg, question important. Just don't think about lower limb. Which the nerve which is carrying the pain sensation into the thigh is lateral cutaneous nerve of thigh. The nerve which is basically responsible for pain sensation into the leg, that will be the saphenous nerve coming from femoral nerve. So it depends upon that which nerve is most likely involved in that case, what case is given to you. Okay, sir.

Moving on. Now, when you look at the hip bone, guys, the two major bony prominences that you can appreciate right now from from this here, that is anterior superior spine and anterior inferior spine. Now, anterior superior spine, as is the origin of the sartorius muscle, and it also provides attachment to the inguinal ligament here. Sartorius muscle origin, and inguinal ligament is also attached to this point here. Whereas AIS, anterior inferior spine, AIS, anterior inferior spine is the origin for rectus femoris. But rectus femoris head, the straight head of rectus femoris will come from here. Reflected head will come from like from above the acetabulum. But straight head of rectus femoris will originate from here. So that is ASIS and AIIS. Not very important, but I feel that bony prominences, especially in the shoulder region and into the hip region are important. Then we have this greater trochanter and lesser trochanter. Now, when you look at the greater trochanter from the front, when you see the greater trochanter from the front, you may appreciate the attachment of gluteus minimus muscle. Gluteus minimus muscle is inserted there. And gluteus minimus muscle, along with gluteus medius, medius, I'll show you the medius from the back side, along with gluteus minimus and medius, both these muscles are responsible for abduction and internal rotation of the hip, guys. Abduction and internal rotation of the hip.

Now, if you look at the same thing from the back side, up pitch is there. Now, if you look at the hip bone and femur from posterior side, greater trochanter is also showing you the attachment of the gluteus medius muscle also. On the lateral side of greater trochanter, we have gluteus medius. On the front of the greater trochanter, we have gluteus minimus. Minimus and medius muscle attached to greater trochanter. Not gluteus maximus, because gluteus maximus muscle is basically attached to the tuberosity present here, which is called as a gluteal tuberosity. It's on the shaft, basically. Gluteal tuberosity. I told you gluteus minimus. So your gluteus medius. So the action of both gluteus minimus and medius muscle is is abduction and internal rotation. It's abduction and internal rotation. Thank you, Tushar. Keep on, keep pushing in between. Yeah. So greater trochanter, if the question is about the greater trochanter fracture, if there's fracture of the greater trochanter, the obviously there's a loss of the gluteus medius muscle and gluteus minimus muscle, and the patient will lose the inability to abduct the hip and internal rotate the hip. Abduction, internal rotation will be affected.

Look at that, guys. That is the gluteal tuberosity. The gluteal tuberosity on the posterior surface of femur is giving insertion to the gluteus maximus muscle. Gluteus maximus is a major extensor of the thigh. Major extension of the thigh. It is not inserted on the trochanter. Gluteus maximus muscle is not on any trochanter. Then we have lesser trochanter, which is giving insertion to the iliopsoas. The muscle that we saw earlier, iliacus and psoas major, guys. Iliacus and psoas major muscle together are called as iliopsoas. And both iliopsoas muscle are inserted on the lesser trochanter. And both iliopsoas muscle are the major flexors of the hip. Main flexor of the hip joint, main flexion, that is by the iliopsoas muscle only, that is iliopsoas. Right? So this is about some of the attachments that you need to know here. If you ask questions about the fracture of the greater trochanter, fracture of the lesser trochanter, so it's not just they will ask you the muscle which is involved in this. They might ask you which movement will get affected. That's why movement will get affected by that muscle involvement. Okay. I'm going to enjoy all these messages, all the the the things that you're typing in between. But after the session, right now.

Look at that spine over there, guys. Ischial spine. One of the recent question on the ischial spine was, what is the level of the ischial spine? The ischial spine lies at the level of the coccygeal vertebrae. But sacrum, coccyx, if the sacrum coccyx is present over there. So ischial spine is present at the level of the coccygeal vertebrae. That was one of the question asked in the recent time. What makes ischial spine so important? The ischial spine lies at the junction of greater sciatic notch and lesser sciatic notch. There are structures, some structures will come out of the greater sciatic notch and enters the lesser sciatic notch. Or because the structures which basically need to leave the pelvis and enter into the perineum, they are pudendal structures. Pudendal nerve, internal pudendal vessels, and nerve to obturator internus. These three structures basically are going to come from the greater sciatic notch, enter the lesser sciatic notch. Or both pudendal structures, P, I, N, pudendal nerve, internal pudendal vessels, and nerve to obturator internus. Especially pudendal nerve is very important there, because if the pudendal nerve is injured on the ischial spine, the muscles of the perineum will get affected. Muscles of perineum, muscles of perineum, bulbospongiosus, ischiocavernosus, transverse perineal, external anal sphincter, perineal muscles, they will get affected. If the pudendal nerve is affected, especially where? At the spine. I hope you read this in OBG also, that is ischial spine, when you have to block the pudendal nerve, block is done against the spine also. Okay. Thank you, guys. Thank you so much. I'm deeply humbled by your messages. Thank you.

Now, iliotibial band or iliotibial tract. What is iliotibial band? The name says a lot. Iliotibial band. That is called as iliotibial band. Now, guys, in the iliotibial band, this white color band that you see on the lateral side is IT band. That is that that is the iliotibial band over there. This iliotibial band is a thickening or the modification of fascia lata. Fascia lata is the deep fascia of thigh. So it's a modification of fascia lata. The deep fascia of thigh. This iliotibial band. There are two major muscles which are inserted on the iliotibial band. One of them is gluteus maximus, and one is tensor fasciae latae. That's a question also that which two muscles are inserted on the IT band. So one is TFL, that is tensor fasciae latae, and gluteus maximus muscle. Both of them are inserted to the gluteus maximus, guys. It was inserted to the gluteal tuberosity also. That was a bony insertion. It is insertion on the band as well. So gluteus maximus and tensor fasciae latae are the two muscles inserted on the IT band. That is one question. Another question that if there is a contracture of iliotibial band, let's say the patient like post guys, in case of poliomyelitis, when there is a contraction of the iliotibial band, what will be the position of the hip joint and what is the position of the knee joint? Your hip joint will come into the FABER position. FABER: flexion, abduction, and external rotation. Look at that. Look at that, guys. So in the hip joint, there is what? FABER. Flexion, abduction, and external rotation. And at the knee joint also, there is a flexion. External rotation of tibia is also there. Tibia will also externally rotate. But I'll tell you the important thing is this flexion. Both the knee joint and hip joint will come into flexion. Hip joint flexion or knee joint flexion. That is because of this in this, in the post-polio contraction of the IT band here. Okay. One more thing. This abnormal positioning, abnormal positioning of this, of the thigh, flexion, abduction, external rotation, it is a normal function of the sartorius muscle. FABER at the hip joint is a normal function of the sartorius muscle. Sartorius muscle is responsible for the flexion at the hip joint, abduction at the hip joint, and even external rotation at, external rotation of the hip joint also. So IT band contraction, that is a normal function of the sartorius muscle at the hip joint. That's why if I take you to this picture where you're looking at the muscles of the anterior compartment of thigh, this is Atlas picture, and that's a cadaveric image here. Now, let's compare both the pictures, guys. First, whenever look at the anterior compartment of thigh, first look at the sartorius being the key muscle over there. When you look at the sartorius muscle, you can divide the entire anterior compartment of thigh into two parts. Everything that

You see, medial to sartorius, that is all muscles of the femoral triangle. If you look at the muscle starting from, like what I told you guys, for the sartorius muscle, it is causing what? Flexion, abduction, external rotation at the thigh, at the hip, and even flexion at the knee joint here. So, contraction of the IT band and the normal function of the sartorius muscle is the same, is more or less the same. Look at medial to sartorius, another muscle. Let me go with that first. Another muscle that, apart from sartorius, is a big muscle that you need to know, that is rectus femoris muscle. Rectus femoris muscle is crossing the hip joint from the front. Remember, rectus femoris muscle was originating from the AIIS, anterior inferior spine. So, rectus femoris muscle will cause flexion at the hip joint and extension at the knee joint. Hip for flexion, guys. This muscle will cause flexion at the hip joint and extension at the knee joint, the rectus femoris muscle, which is exactly the antagonist or opposite of hamstring muscles. The hamstring muscles, like semitendinosus, semimembranosus muscle, they will do the extension at the hip joint and flexion at the knee joint here. So, remember that rectus femoris muscle, which is causing flexion at the hip and extension at the knee, is exactly antagonist to the hamstrings. Semitendinosus, semitendinosus, semimembranosus, all these muscles will cause flexion at the knee and extension at the hip here.

If you look at medial to sartorius now, medial to sartorius, guys, you are able to see the muscle that is coming from the iliacus. You already saw that. Next muscle to that is what? Obviously, psoas major. You also saw that. Next to that is, we're going toward the medial side now, pectineus. And finally, we have a muscle called as adductor longus. And iliacus, psoas major, pectineus, and adductor longus. These four muscles, in that sequence from lateral to medial, are all forming the floor of the femoral triangle. These four muscles are forming the floor of the femoral triangle. Triangle. These muscles are the floor of the femoral triangle, right? That is the floor of the femoral triangle, that is the four muscles over there. Okay.

So, from this, like in INIC, they gave the muscle sartorius, and the question was about the action of this muscle, guys, in the categorical image-based question. I know that people generally are very scared of the categorical picture. So, categorical image, this categorical image, that. But, you know, if you pick up, if you just look at the actual categorical picture asked in the exam in the recent four or five years, you will notice one thing, that the question could be difficult. They might ask you detailed action of the muscle or something, but the image and the muscle asked is usually very simple. Examiner is not that cruel. They will give you muscle, articular genome muscle to identify, nothing like that. It's a big muscle, like muscle like biceps or triceps or any, you know, brachioradialis muscle. Muscle question on the pronator teres was asked in the exam. The question on the sartorius muscle is asked in the exam. Two basic muscles. This muscle, you have to identify. I'm pretty sure that people, out of any muscle that you see in the picture, the one muscle which I'm sure everyone is able to identify is sartorius. And that's even the examiner knows. Key, I have to give a picture where the muscle is identifiable. Now, what I can do is, I can ask the question with a little twist. I can ask you detailed action of the muscle or something about the nerve supply, something. So, please don't be scared of the image-based question, because in the image-based question, the easiest part is the image. The question might trouble you a little, but when you look at the image, you will not have a difficulty in identifying what nerve, what artery, what muscle, what joint, what ligament is shown to you. That I can promise you. That's the history of this exam shows you. Although in the grand test, in the, in the, in the, in the different tests which are available at different platforms, the question bank, when we have to formulate the question, different faculty have to formulate the questions, they actually end up giving difficult questions, difficult images here, difficult images. And trust me on this.

Now, this is a femoral triangle, guys. That's a femoral triangle. And we already saw the floor of the femoral triangle. Now, you look at the contents of the femoral triangle. The only thing I want to notice in the femoral triangle, very basic, in this, in the femoral triangle, that's the femoral nerve, which is the lateral most. The major content, lateral most content, is femoral nerve. And then we have femoral artery and the femoral vein. But the thing is, femoral artery and femoral vein are inside the femoral sheath. That's the important thing. Femoral nerve is a content of femoral triangle, but femoral nerve is not the content of femoral sheath. Femoral sheath content may we have femoral artery, we have femoral vein, and we do have some lymph node also, called as a lymph node of Cloquet. But femoral nerve is not the content of femoral sheath here. Right. Yeah. The femoral nerve. So, the, the relation is like, for lateral to medial, we have nerve, then we have artery, then we have vein. So, it's NAV from lateral to medial. But remember, artery and vein are the ones which are inside the femoral sheath. Nerve is just outside or just lateral to the femoral sheath in the femoral triangle. That's what you have to remember in this.

Okay. Now, in the gluteal region, the questions in the gluteal region, it's not the gluteal region. Questions are challenging because the question is generally about one muscle, that is gluteus medius muscle. I mean, that's the most commonly asked question. Let me tell you one thing, guys. They obviously will not give you the gluteal region picture like this, because the muscle that you're looking at right now on the screen is gluteus maximus. Gluteus maximus intact. So, obviously, the examiner has to cut the gluteus maximus muscle and then show it to you. So, look at this picture now. Now, when you look at the gluteus maximus muscle is cut on the other side here. You just have to identify this muscle, but that muscle is piriformis. You identify the piriformis muscle, and it is sorted. Why I'm saying it is sorted? Because if you see the nerves and vessels coming out above the piriformis, those are superior gluteal nerves and vessels. If you see the nerves and vessels coming out below the piriformis, they are inferior gluteal nerves and vessels. And the muscle that you're looking at over there, guys, these muscles, that muscle that makes all the difference. This muscle, say gluteus. They ask you the question, that muscle is gluteus medius or maybe minimus also. The reason gluteus medius muscle is so important, because as you already know, gluteus medius muscle is responsible for abduction and internal rotation of the hip. Abduction and internal rotation, especially abduction, remember that. So, if gluteus medius muscle is not working, then, guys, gluteus medius muscle of the right side is not working. So, every time I'll take the left foot off the ground, my left pelvis will drop. My right gluteus medius is not working. So, my left pelvis will drop here. So, look in the normal condition, this gluteus medius muscle is working, and that is maintaining the pelvis of the other side. Look at the right gluteus medius is working, and left pelvis is leveled. But if the superior gluteal nerve, which is supplying it, if the superior gluteal nerve is injured, and the gluteus medius or minimus muscles are not working, then the right gluteus medius injury will cause the left pelvic drop. You can see that's a pelvic drop over there. Can you, can you see that arrow over there? That's a pelvic drop, and that is the Trendelenburg sign. Simple fun in Trendelenburg sign or Trendelenburg test. Everything is ipsilateral except pelvic. This is a, this is the right side gluteus medius muscle. It's a right side nerve injury. It's a right side Trendelenburg sign. This patient will do the right side lurching also, because the pelvic drop is on what side? Left side. So, simple pelvic drop is on the contralateral side in Trendelenburg sign. Right side Trendelenburg sign means right side injury, right side muscle gone, right side patient will do the right side lurching, but the pelvic drop will be seen on the opposite side, on the contralateral side. Okay.

Okay. Coming to the nerve, the one major nerve of the lower limb without which this topic is never complete, that is the sciatic nerve, guys. The sciatic nerve, which is coming from this L4, L5, S1, S2, S3 lumbosacral trunk and S1, S2, S3, the first three sacral root values. Now, the nerve runs into the gluteal region, then comes into the hamstring region, and then this sciatic nerve in the fossa, that dimple fossa, in the popliteal fossa. First, the nerve, in the fossa, the nerve will divide into the common peroneal and tibial. First, the sciatic nerve in the gluteal region passes deep to piriformis, guys. It is not supplying piriformis. It is passing deep to piriformis muscle. It reaches the hamstring compartment. It supplies all hamstrings. All hamstring muscles supplied by the sciatic nerve: semitendinosus, semimembranosus, biceps femoris. And then the nerve reaches the popliteal fossa. And in the upper part of the popliteal fossa, only the nerve divides into the tibial nerve, which runs straight, and the common peroneal nerve, which is going to wind around the neck of the fibula. Look at that. The nerve which goes around the neck of the fibula, that's a CPN, common peroneal nerve. And after winding around the neck of the fibula, the nerve is going to divide into a superficial and a deep peroneal nerve. Look at that. That is a superficial peroneal nerve and the deep peroneal nerve. So, now we have three nerves for the lower leg. Tibial nerve will supply the posterior compartment, that is plantar flexors. Superficial peroneal nerve will supply the lateral compartment, that is everters. And deep peroneal nerve will supply the anterior compartment, which are dorsiflexors. Now, tibial nerve is supplying the plantar flexors, which you and I have to write this. Tibial is posterior because tibial is posterior is the inverter also. It is one of the inverter. So, tibial is supplying, guys, leg. So, the posterior, the calf muscles are supplied by tibial nerve, plantar flexors, which are doing the plantar flexion, and even some of the inverter also, some of the inverter also. Superficial peroneal nerve supplies peroneus longus and peroneus brevis. And peroneus longus and peroneus brevis are everters. Okay. And deep peroneal nerve is going to supply the, the dorsiflexors, the muscles of the anterior compartment. Tibial nerve, after supplying the plantar flexors, after supplying the tibialis posterior, what they're going to do in the foot? They are going to divide into the medial plantar nerve and lateral plantar nerve. Medial plantar nerve and lateral plantar nerve, which is going to supply all the muscles in the sole of the foot. So, tibial nerve is a big nerve, guys, because it is first supplying all the calf muscles and then supplying every single muscle in the sole of the foot. Key superficial and deep peroneal nerve. As you can see, the superficial peroneal nerve supplies everters. Peroneus longus and peroneus brevis. Deep peroneal nerve supplies the dorsiflexors, the dorsiflexors, and supplying tibialis anterior, which is an inverter. The point is, some inverters are supplied by the tibial nerve, and some inverters are supplied by the deep peroneal nerve. Now, what is the fate of superficial and deep peroneal nerve? Superficial and deep peroneal, what they will do? They will reach the foot. The superficial peroneal nerve, the name says, guys, superficial, that is the main nerve supplying the skin on the dorsum of the foot. But the deep peroneal nerve, it just supplies the skin in the first web space. The skin between the great toe and the second digit, that space is supplied by the deep peroneal nerve. Now, listen to this once again here. Tibial nerve supplies what compartment? Posterior. Deep peroneal supplies what compartment? Anterior. And superficial peroneal supplies what compartment? Lateral. Now, look at this. If the tibial nerve is injured, now, just focus on that, guys. If the tibial nerve is injured, then which muscles are? Plantar flexors are gone. Tibial is posterior. Inverters are gone. If common peroneal nerve is injured at the neck of fibula, which is the most common injury, by the way, if you look at here, then we have dorsiflexors, everters will be gone, mainly. Look at the consequences. If the tibial nerve is injured, then we said which muscle, mainly the dorsiflexors are mainly affected. So, I'm sorry, plantar flexors are mainly affected, and the inverters are also affected. So, patient's foot will come into what position? Dorsiflexed and inverted position. Dorsiflexed and inverted. And this dorsiflexed and inverted foot is a calcaneal valgus. And this patient, as you can see, is walking on heels only. Heel walk, which is called as a calcaneal gait. The patient will have a gait called as a calcaneal, walking on heel, that is a calcaneal gait. But if there is a common peroneal nerve injury, now, in common peroneal nerve injury, there is dorsiflexors and inverters are gone. If dorsiflexors and inverters are gone, then patient will have what? Foot drop and inverted foot. Drop and inverted foot is called as an equinovarus position of foot. Here, foot drop and inverted, that is equinovarus position. When foot is equinovarus in position, this patient will take a very high step to clear the foot off the ground, which is called as a high-stepping gait. So, tibial injury, there will be calcaneal gait. But in case of the, in case of the common peroneal nerve injury, which is a more commonly asked question, there is a high-stepping gait will be there. The high-stepping gait will be seen.

Two relations of the vein that you should know in the lower limb: the great saphenous vein and the short saphenous vein. The great saphenous vein, I'm sure you all know, guys. Great saphenous vein, when it starts from the dorsum of the foot here, it runs onto the medial side. And the short saphenous vein, it is running on the lateral side and it drains into the vein, guys. Great saphenous vein, it drains into the femoral vein. Whereas a short saphenous vein, it drains into the popliteal vein. The important thing is, great saphenous vein, because the nerve that you see running along with that is a branch of femoral nerve, and that is a saphenous nerve. It's a saphenous nerve which is running with the great saphenous vein. So, if you're taking a graft of the great saphenous vein in CABG, then saphenous nerve is likely to get injured, and the patient will have a sensory loss on the medial side of the leg and foot till grade two. But if you take a graft of the short saphenous vein, then the vein nerve running along with that on the lateral side, that sural nerve might get injured, and this patient might have a sensory loss on the lateral side of the leg and the foot. Right to the great saphenous vein, saphenous nerve. And short saphenous, sural nerve. Present. Saphenous nerve present on the medial side. It's the longest cutaneous nerve in the body. And sural nerve is present on the lateral side, running with the short saphenous.

Ligaments of foot and ankle, guys. What about the ligaments? Just a couple of ligaments of foot and ankle to conclude this lower limb part. Mainly, some of the important ligaments which I want to mention here. Maybe some of the ligaments are discussed with you in the ortho class. But if I may take your attention to some of the important ligaments like this one, guys. Look at this ligament which is called as a spring ligament. The reason we call it a spring ligament because it is supporting the head of the talus bone. That bone over there is a talus bone, and this ligament which is supporting it is a spring ligament. Spring ligament is stretching between the calcaneum and navicular. This bone here is calcaneum, and this bone here is navicular, and that's why this ligament is also called as a plantar calcaneonavicular ligament. Spring ligament is also called as a plantar calcaneonavicular ligament. And I told you, it's a main ligament of the medial longitudinal arch. This question is asked in the exam, that which ligament supports the head of the talus, and that is the, that is, that is this, what do you say, spring ligament is there. Then we have the ligament called as a long and short plantar calcaneocuboid ligament. Honestly, not very important because these ligaments are supporting the lateral arch. So, important ligament because lateral arch is not that concave, like compared to the medial arch. So, out of these, I would recommend you remember at least spring ligament, that is plantar calcaneonavicular ligament, supporting the head of the talus, okay? That is supporting the lateral arch, not very important, okay?

Now, again, the same picture, but this time, this is a spring ligament. If a patient, this is a spring ligament, but I'm not focusing on spring ligament. Look at the ligament called as deltoid ligament, which is having three fibers. Look at the three bands of the deltoid ligament. The question asked on the deltoid ligament is, key, which bone it is attached to? Deltoid ligament is attached to the tibia, that's the tibial malleolus. It is attached to the navicular bone, that is navicular there. It is attached to the calcaneum, and the posterior fiber are attached to the talus also. So, tibia, talus, navicular, calcaneum, be the deltoid. This, this delta-shaped ligament, it's a very, very strong ligament. And this deltoid ligament is giving attachment, I'm sorry, this deltoid ligament is giving attachment, is attached to the medial malleolus, to the navicular, to the calcaneum, and to the talus bone here. This is one of the old questions asked by the Puchawa question exam, that deltoid ligament is not attached to which bone, and medial cuneiform was given in the question in the option. Very strong ligament. The injury is, it's not an easy to have an injury to the deltoid ligament, because foot injuries are usually on the inside. Inversion injuries are more common, not the injury. But if there is an eversion injury at all, like in Pote's fracture, then you may have a deltoid ligament injured, which is a rare thing to see. It's such a strong ligament. Ligament to bone to, that's how, how strong this deltoid ligament is.

But the ligament which is very vulnerable to injury, guys, is a ligament present on the medial side. Now, look at this ligament present on the medial side, which is having one band on the posterior side, one band middle, and one is anterior, and that is called as a lateral ligament of the ankle. Out of which, the anterior talofibular ligament is the most important. We have posterior talofibular also. We have this is a posterior talofibular. This is calcaneofibular. And there is anterior talofibular. But anterior talofibular ligament is more important to remember, because inversion of the foot is, inversion injury of the foot is more common. And if there is an inversion injury of the foot, the anterior talofibular ligament is most likely to get affected. That's a question asked, that which ligament injury is most commonly seen in the inversion, in the inversion of the foot, and that is anterior talofibular ligament. That, that's an important question from this part here. Okay.

Now, when you look at the ligament of the foot, one more ligament which I want to take your attention to, guys, and that ligament is called as a bifurcate ligament. Look at that circle over there. That ligament, can you see the bifurcation there? One band of this ligament is, the stem of this ligament is attached to the calcaneum. That's a calcaneum bone. That over there is navicular, and this over there is a cuboid. So, one band is going toward the navicular bone. One band is going toward the cuboid bone. So, this ligament is called as a bifurcate ligament. And when you say bifurcate ligament, you have a calcaneonavicular ligament part of it, from calcaneum to navicular, and we have a calcaneocuboid part of it. In the inversion, if the foot is in the plantarflexed position, plantarflexed foot, if it is getting inverted, anterior talofibular ligament is most commonly injured. But yellow ligament injured. This ligament is also likely to get injured in the inversion injury of the foot, called as a bifurcate ligament. There are two bands of this ligament, called as a calcaneonavicular and calcaneocuboid, as you can see in the picture. And that's a cadaveric view of this bifurcate ligament here. Look at that, the calcaneonavicular, calcaneocuboid part, and the calcaneonavicular part of this bifurcate ligament here. Okay.

Slides. And then I'm going to give you a break after this, guys. Now, look, this is a picture of the serous acinus. Please understand that what I'm trying to show you in this picture. When you look at the serous acinus, one thing is to be noted that I'm just enlarging this picture as much as I could. If you look at the serous acinus, that's the maximum. Yeah, that's maximum. Actually, if you look at the serous acinus, guys, one thing, if you, if you note that, look at this basal part here, and look at this apical part, which is granular, and all the nuclei are present toward the basal side. Can you see all the nuclei present toward the basal side? If you look at any acinus, the nuclei present toward the basal side. Yeah, they're all present toward the basal side. In the serous acinus, that is a thing to be remembered. The cells are pyramidal. Now, you may not be able to notice the shape of the cell. It is a very good picture. That's why you're able to see rough endoplasmic reticulum are present at their base. That's why they're basic. If you look at clearly, it looks like there's a blue line toward the basal side. The basophilic cytoplasm is there because of rough ER. And we have apical region is having the secretion granules are there, the zymogen granules are there. Then look at the mucous acinus. In the mucous acinus, we have a foamy cytoplasm because when you treat the mucus, mucous acinus with the alcohol, the mucus is washed off. And the nuclei are flat and basal. Look at all the nuclei which are flat and basal nuclei are present here. So, in the nucleus and the cells are columnar. Again, you may not be able to notice the shape of the cell, but you can see the flat nuclei, basal nuclei, and the foamy appearance of the cytoplasm. Carrier. So, that's how the serous and mucous acinus generally they look like. It's a very good image of the serous and mucous. Honestly, I'm not expecting you to give you such a high-quality images, but we have to, like, when you. Okay. So, and and that's a serous and the mucous there. Just one second. Lisfranc ligament is nothing. It is just connecting the medial cuneiform to the base of the second metatarsal. Medial cuneiform to the base of the second metatarsal. That is Lisfranc ligament. That is a Lisfranc ligament complex. Okay.

So, once you know that how the mucous and serous is going to look like. Now, look at this gland. That's a mixed gland. Which mixed gland can have foamy cytoplasm? So, you can see the, the, the mucus also and serous also. It's basically the mucous acinus is capped by the serous cells, and it is called as a serous demilune. It's an artifact, guys. It's an artifact while, while we prepare the slide, this artifact is formed. That is called as a mixed salivary gland, where we have the serous demilunes. They are there. Mucous acinus, they're capped by the serous cells. Now, serous, serous. There is. And I'm saying so much of serous acinus again. It is mainly because of this slide. If you look at this picture, this slide looks like a serous acinus. Rounded cell toward the basal side. That's a serous acinus. So, looking at this. Okay, it's a serous acinus. This could be parotid gland? No, sir. It's not parotid gland. When you look at this slide, it is not a parotid, though it looks like a parotid gland because these are serous acini, and parotid is a serous gland. But this is not a parotid gland. It is a slide of a pancreas. When they give you the slide of the pancreas, there are very good chances that they will give you a lightly stained zone separately, which is basically showing you the islet of Langerhans, something like this. This is like an islet. You can see in this picture, that's the islet of Langerhans. So, maybe by looking at the islet of Langerhans, you can identify it is pancreas. But let's say if the examiner is very cruel and is not giving you this region and giving you only the picture that you see in the corner above, and you still have to identify pancreas. Yeah, it is a parotid gland. Then the thing is, if you look at the cell, guys, if, if you look at this cell, can you see some nuclei present in the center also? Can you see some nuclei present in the center also? Can you see some nuclei present in the center also? In the acinus, we have some nuclei present in the center, and these cells are called as centroacinar cells. Now, that's the feature, guys. Forget about this island of Langerhans problem, but if it is not given, look at the acinus and look at those cells present in the center. These are called as centroacinar cells. The duct. If this is an acinus, and this is a duct, it should be like acinus is there, and then we have duct starting like this. But imagine if the duct is starting inside the acinus only. So, you will see that the, the, the cells of the duct can be seen within the serous acinus only, and these cells are called as duct cells of the, of the acinus. Centroacinar cells. That is a feature of the pancreas. Parotid gland slide, you will not see any cells in the center. You will only see cells on the side only. That's why these two are the most confused slides to each other. If the eye of Langerhans is not given, pancreas or parotid, identify both. See this acinus only. But if you see some nuclei present inside the acinus, mark it pancreas. These are cells are called as centroacinar cells or central cells. What is this again? It's a previous picture. Cytoplasm looks like it's mucus. It's not a mucous acinus. Yeah. Acinus. First of all, look at the cluster of these cells. There is no lumen present over there, and they are present close to the root of the hair follicles. These are the sebaceous glands, guys. Sebaceous glands. I'm sure you read about sebaceous glands. They are the ones which are holocrine glands. Question, as much as they have given this picture, that what kind of secretion is seen in this, in the sebaceous gland which you're looking at over there? The kind of secretion is what? Holocrine secretion. The cell itself will disintegrate into the secretion. Here, that is called as epithelioid. Epithelioid. Epithelioid in pathology are the macrophages cells. Those the, the big macrophages cells which is called as epithelioid. You, in general histology, epithelioid is a name given to the cells which do not have a free surface. The cells which do not have a free surface. Look at all these cells are clustered together. They don't have any free surface. They're all facing each other. Like in islet of Langerhans, it's epithelioid. Sebaceous gland, epithelioid. Uh, the, the cells of corona radiata around the ovum, the epithelioid. Leydig cells, epithelioid. These are some of the examples of epithelioid. The cells which do not have a free surface. In cells, free surface. They're all facing each other only, and that's why there is no free surface of these cells. These are called as epithelioid. So, there are two different epithelioid. One is the epithelioid, the macrophage cells that you said read in pathology, those are different epithelioid. In pathology, also, in general histology also, there is a term called as epithelioid. Epithelium, achypheric epithelioid. Epithelium is a lining epithelium with a free surface. Epithelioid are the cells which are without free surface. These are called as epithelioid. Even sebaceous gland is an example of epithelioid. Without surface, without free surface. Exactly.

So, now let's start with the head, neck, and face. Um, in head, neck, and face, I'm going to start. I'm going to go in the, in the series of how I go in my lecture. So, I'll start with the cranial nuclei and cranial columns and some parasympathetic ganglia first. So, guys, like, look in the cranial nuclei column. Now, the first thing, I mean, because it's a, it's a one-shot program, so we don't have to go into the details of how these efferent columns, columns are formed. So, in a simple way, if you know the first three efferent columns: the first three efferent, general somatic efferent, special visceral efferent, and general visceral efferent. If you know the first three here, then you know the next three also, because they are like mirror images only. Like for this GVE, for this, if this is GVE here, one second, there is GVE. So, we have a corresponding GVA. For SVE, this is corresponding SVA. And for this GSE, there is corresponding GSA. So, three efferent and three afferent columns. There is one more. They look, you're looking at right now. Okay. Uh, so, GSE, SVE, GVE. And then we have the three columns, the afferent columns: the GSA, GSE, general somatic efferent, guys. The general somatic, the word somatic is for the extraocular and tongue muscles, the extraocular muscles and tongue muscles, the somatic muscles. So, third nerve nucleus, fourth nerve nucleus, sixth, and 12th. Third, fourth, and sixth nerve will supply extraocular muscles, and 12th nerve will supply the tongue muscle. They'll supply the tongue muscle, right? So, they are the ones which are present in the first column. But the first column, the nuclei which are present in the first column are the ones which are basically supplying extraocular and tongue muscles. SVE, special visceral efferent. Now, special visceral efferent is about pharyngeal arches. Pharyngeal arches are supplied by what nerve? We have mandibular nerve for the first arch. We got a facial nerve for the second arch. And we have a nucleus ambiguus. It is a combined nucleus of 9th, 10th, 11th nerve, cranial accessory. That nucleus is called as nucleus ambiguus. That is for the ninth, tenth nerve. So, first column, we have, we have nuclei supplying extraocular and tongue muscles. Second column, we have those nuclei which are supplying the pharyngeal arch muscles. Then, the first two columns, the, the similar thing about the first two columns is the donor columns are to supply the, what muscles? Skeletal muscles. They're supplying skeletal muscles. And that's why we have a third column, that is general visceral efferent. General visceral efferent is to supply the smooth muscles and glands. Now, when I say smooth muscles and glands, they are supplying Edinger-Westphal, superior salivary, inferior salivary, dorsal nucleus of vagus. We'll talk more about this column here, but this is the column which is basically, this is the column which is going to supply the extra, going to supply the smooth muscles and glands. And that's why this column is also called as a parasympathetic column. I'm, column detail discuss, we'll talk more about this column separately in detail. Edinger-Westphal, the two salivary nuclei, superior, inferior salivatory, and dorsal nucleus of vagus. That's efferent. Now, coming to afferent columns. The GVA, SVA, general visceral afferent, and special visceral afferent. General sensation, visceral, yeah, taste sensation, visceral. They will all come into one nucleus only, and that is called as a nucleus of tractus solitarius. It is the only nucleus present combined in two columns. Just imagine how important this nucleus is. For two columns, we have one nucleus called as the nucleus of tractus solitarius. Nucleus of tractus solitarius, NTS. Okay. Okay. Then we have a column called as the GSA column. Go, just break it down. General somatic afferent. General because general sensation. Somatic, that means from body wall, from the skin, from the dermis, from the muscle, body wall sensation, afferent. So, any nuclei which is going to take the general sensation from body wall will come into this GSA, general somatic afferent. So, there is a trigeminal nuclei here. This big nucleus here. Again, I'm going to discuss this nuclei more in detail. It is called as a trigeminal nuclei, having three parts, that is present in GSA column. Right? General somatic afferent. Despite of having these six columns, we have one more column after that, guys, and that is called as SSA column. Special somatic afferent column. SA, special somatic afferent column is a column for the vestibular and cochlear nuclei. Special sensation, be, but they're coming from somatic structures. So, we have a separate column for vestibular and cochlear nuclei. Vestibular or vestibular and cochlear nuclei. Right? These are the columns we have. Now, I know that in the exams, they're not going to ask you all these columns in that kind of detail. One important column will be GV, one is GSA column. Discuss. See, the nerves which are parasympathetic in nature, they are more important nerves to be asked in the exam. Parasympathetic nerve concept: 3, 7, 9, and 10. 3, 7, 9, and 10 are parasympathetic. I'm sure everyone knows that. Now, third nerve, you can see, third nerve comes into the GSC column. And third nerve belongs to Edinger-Westphal also. So, there are two columns for third nerve: that is GSE and GV. Third nerve, two columns, guys, that is GSE and GV. GSE and GV is the column for third. Seventh nerve, ninth nerve, and 10th nerve. Now, that is easy. Seventh nerve, ninth, and 10th nerve are related to all columns except first and last. Look at that. All these columns, first, leave the GSE, and leave the last column, that is SSA. Leaving first and last column. All other columns are related to the, to the seventh nerve, to the ninth nerve, and 10th nerve. Nobody in the exam is going to ask you the reason for that. You just need to know the answer, which columns are related to the seventh nerve, ninth, and 10th nerve. All you have to think about here is, sorry, column except GSE, that is first one. Except the last one, that is SSA. All are there. And I already told you that for third nerve, we have two columns, that is GSE and GV. GSE is there, and GV is there. That is for third nerve. So, out of all the cranial nerves, at least, at least remember these nerves, that is 3, 7, 9, and 10. But let's not stop here, guys. Let's talk about every cranial nerve. Now, look at this picture here. First, GSA column, general somatic afferent. We said, what is, what is there in the general somatic afferent column? In a general somatic afferent column, we have this big nuclei called as a trigeminal nuclei. And this trigeminal nuclei, we said it is having three parts. One is called as a mesencephalic nucleus, guys. Mesencephalic nucleus, which is present in midbrain. Then we have principal sensory nucleus, which is present in pons. And then we have spinal nucleus, which is present in the medulla, and it even goes till the C2 level of the spinal cord. It even goes to the C2 level of spinal cord. That is mesencephalic, the spinal nucleus here. Mesencephalic nucleus is responsible for receiving proprioception. Principal sensory nucleus receives touch and pressure. And spinal nucleus is the one which receives pain and temperature. Pain and temperature. Mesencephalic nucleus is an important nucleus. This is something which is repeatedly asked in the exam because mesencephalic nucleus. It is not just the nucleus for proprioception. It is a nucleus for the jaw reflex or masticatory reflex, and it is the only site, a site in the central nervous system where we have pseudo-unipolar neurons are there, guys. It is a center for jaw reflex. Number one. It is a center for the jaw reflex, mesencephalic nucleus. And it is the only site for what neuron? Pseudo-unipolar neuron in CNS. Outside CNS, example. Inside CNS, it is the only example where we have pseudo-unipolar neurons. That is mesencephalic nucleus. It's an important question, and they've asked this question more than once. So, that is something about the GSA column. The big trigeminal nuclei is there, and that's the function of these individual nuclei, especially mesencephalic nucleus is important.

Now, coming to the GVE column, guys. Third column, column GV. This, we have got Edinger-Westphal, superior salivary, inferior salivary, and dorsal nucleus of vagus. Now, Edinger-Westphal is there. Superior salivatory nucleus, inferior salivatory nucleus, that is in the pons. And we have a dorsal nucleus of vagus. What these nuclei are doing? Which nerve they are connected to? What ganglion they are going to relay in? Which gland they are going to supply? Let's discuss that. Edinger-Westphal, as I'm sure you all know, Edinger-Westphal. The nerve for the Edinger-Westphal is a third nerve. So, it's a third nerve which is basically carrying this, you know, information from the Edinger-Westphal nucleus. It is going to relay into the ganglion. Which ganglion, guys? Ciliary ganglion. That's a ciliary ganglion. And then from the ciliary ganglion, the multiple short ciliary nerves will come out, and these short ciliary nerves will go out and supply the sphincter pupillae and ciliaris muscle. So, that's the function of Edinger-Westphal. The general visceral efferent, the parasympathetic column, that is Edinger-Westphal nucleus, which is having a nerve, third nerve, relays into the ciliary ganglion, and that supplies sphincter pupillae and ciliaris muscle. Superior salivatory nucleus. The nerve for superior salivatory nucleus is facial nerve. And this facial nerve divides into two branches. I mean, I'm talking about two branches of facial nerve. One of the branch of facial nerve that I'm talking about is a greater petrosal nerve, GPN. This greater petrosal nerve, it relays into the new ganglion, which is called as a pterygopalatine ganglion, subganglion. It's the largest parasympathetic ganglion. That is pterygopalatine ganglion. And once the greater petrosal nerve relays into pterygopalatine ganglion, the postganglionic fibers will go and supply lacrimal gland and some supplies the nasal gland also. But lacrimal gland is important to remember. But it's lacrimal gland and even nasal glands are also supplied by this nerve. Nasal gland. Another branch of facial nerve, guys. Another branch of facial nerve is chorda tympani. Now, chorda tympani nerve also goes and relays into the new, into, I'm sorry, relays into the ganglion. And this time, the ganglion is the submandibular ganglion. It's a ganglion which is present somewhere here, submandibular ganglion. And once it relays into the submandibular ganglion, the postganglionic fibers are going to supply the submandibular and the sublingual gland. Supply submandibular, sublingual gland. This also helps remember that the facial nerve, guys, facial nerve response. Facial nerve is one nerve connected to two parasympathetic ganglia, and it is responsible for supplying lacrimal gland, nasal gland, submandibular, sublingual gland. Majority of the glands are supplied by the facial nerve only, using two ganglia, that is pterygopalatine and submandibular ganglion. Then comes inferior salivatory nucleus. The nerve for the inferior salivatory nucleus is facial nerve. The ninth nerve, sorry, glossopharyngeal nerve, to be more precise. Jacobson's nerve and lesser petrosal branch. Then ninth nerve, this ninth nerve via lesser petrosal nerve relays into the otic ganglion. This time, the ganglion is otic ganglion. And the postganglionic fibers from otic ganglion are going to supply the parotid gland, guys. It is for the parotid gland here. So, in a way, I can say facial nerve takes the responsibility of the lacrimal gland, nasal gland, submandibular gland, sublingual gland. But parotid gland is a responsibility of what nerve? Ninth nerve. So, facial nerve supplies most of the glands in head and neck, but ninth nerve will take care of the parotid gland. Dorsal nucleus of vagus, guys. Dorsal nucleus of vagus. Name says it's a vagus nerve coming out from there. And the responsibility of the vagus nerve is to supply the smooth muscles and glands in the thorax and abdomen. So, no, it is not there is no ganglion for vagus nerve in head and neck. The ganglion for vagus nerve are lying in the thorax and abdomen, because the responsibility is to supply the smooth muscles of thorax and the abdomen. So, this is something about the. Yeah. This is about the, the GVE column. It's an important column. This column, question, they can ask you that which, first of all, it's a parasympathetic column, guys. Number one, it is related to parasympathetic. Look at the third nerve, seventh nerve, ninth, and 10th. These are all parasympathetic cranial nerves. They can ask you which nucleus is connected to what nerve, which ganglion they will relate to, what gland is supplied by them. So, I, I, I feel there are a lot of questions which are present on this slide here. So, please make sure that you, when you revise it, just revise it carefully.

Moving on, we already said parasympathetic nerves: 3, 7, 9, and 10. Now, if I talk about all cranial nerves from 1 to 12. Now, which column they will lie to? First and second nerve. So, there is no nucleus for first and second. So, forget about it. Third nerve, we already said third nerve belongs to the GSC column and GVE column. That was easy. Okay. If you think of fourth nerve, guys, fourth nerve supplies only extraocular muscles and nothing else. And extraocular muscles come into the GSC column. So, fourth nerve is only having one column, that is the first one. GSC column is there. Fifth nerve. Fifth nerve, if you remember, fifth nerve comes into the second column, that is SV, because it is supplying the muscles of mastication. And fifth nerve also, trigeminal nuclei. Trigeminal nuclei lies into what column? GSA column, guys. GSA column is also. So, there are two columns for fifth nerve. One is SV to supply the muscles of mastication, and to take the sensation from the face, the trigeminal nuclei. The GSA column is there. Sixth nerve. Again, I told you, sixth nerve, guys, we only have one column. It is supplying lateral rectus, and that's it. So, only again, first column, GSC column is there. Sixth nerve, nothing else. Seventh, ninth, and 10th nerve. What I told you, guys? 7th, 9th, and 10th nerve, they have all columns except first and last. Look at that. Look at the check over there. The ticks. All 7th, 9th, and 10th. All the columns except first and last. First name, last name column. Eighth nerve. Remember when we drew that table, what was the last column? The last column was SSA column. Special somatic afferent. So, eighth nerve, vestibular cochlear nerve belongs to this SSA column. Special somatic afferent column. 11th nerve. Now, that's interesting, because this is, I believe, that they can kind of trick you on. 11th nerve also comes into two columns. Column. Say, because 11th nerve is having two parts: one is cranial accessory, and one is spinal accessory. Now, guys, cranial accessory nerve comes into this part, that is cranial accessory here. But spinal accessory, because it supplies the skeletal muscle, the somatic muscles outside. So, it actually comes into GSC. Although we are not able to see it on that, on that table, because the table belongs to only brain stem. This is beyond brain stem. The spinal accessory nucleus is present in the spinal cord. But remember that the spinal accessory nerve, that is cranial accessory. But the spinal accessory nerve, they belong to the GSC column. So, the first, they are for the 11th nerve. 11th nerve, that, that's a tricky part here. 11th nerve is having two columns: first two columns, GSC and SV. And 12th nerve, hypoglossal nerve. Again, hypoglossal nerve just supplies what? Tongue muscles. And tongue muscles, that is the first column only, that is GSC column. That's it. Although you're looking at all the nerves and their columns here. But I still tell you, guys, only focus on third, 7th, 9th, and 10th. 3, 7, 9, and 10. The parasympathetic cranial nerves are the ones for which you have to remember the columns. Say, column that is still okay. That will do. Yeah. Mayang is focusing on Bugatti only outside. Bugatti is not a very famous bike here. You know, Bugatti is a, or bikes are other superbikes are better.

So, guys, rule of 17 in the cranial injuries. The rule of 17 is something which is, which is very important to, to, to know about, because a lot of image-based questions can be answered from this rule of 17. Now, when I say rule of 17, guys, it means 10 + 7 is 17. 12 + 5 is 17. You all know about the rule of 17. I be, 10 + 7, we have written together because 10th nerve and seventh nerve, if there is an injury to 10th nerve and seventh nerve, the deviation will be seen toward the contralateral side. If the right side nerve is injured, the structure will deviate toward the left side. Similarly, in case of 12th and fifth nerve, when 12th and fifth nerve are injured, the deviation of the structure will be seen toward the ipsilateral side. 10th, when you look at the 10th nerve, can you see this picture? The uvula is deviating toward what side? The uvula is deviating toward the left side in this picture. That means it's a right vagus nerve injury. If you look at this picture, facial nerve, look at the angle of mouth, guys. Corner of mouth, it is deviating toward what side? Left side. It's a left deviation of the corner of mouth. So, it is a right side facial injury, because strong muscles are pulling. So, it makes sense. 10th nerve and seventh nerve injury, may the deviation is seen. Sorry for that sound. Away from the, away from the nerve side. Right. Then we have 12th and fifth nerve. 12th and fifth nerve. In case of 12th and fifth nerve, the deviation will be seen on the ipsilateral side. Now, the tongue deviates, guys.

If you ask the patient to protrude the tongue, and if you see the tongue deviating toward one side, whichever side the tongue is deviating, there is a case when the tongue is deviating toward the left side. So, left side hypoglossal injury is there. And similarly, like in this case, if the jaw is deviating toward the left side, it's a left side. I'm sorry, it's a left side trigeminal injury. So, it's very, but remember in both these cases where the ipsilateral deviation is seen, you have to ask the patient to do something. Like in the first case, you need to ask the patient to protrude the tongue, then only you can see the deviation. In this case, you need to ask the patient to open the mouth. When you ask him to open the mouth, then you see the jaw is deviating toward one side. But if the tongue deviates to whatever side or the jaw is deviating to whichever side, the same side nerve injury will be there. So, it's a very good picture from an area from where image-based questions can be asked. They might give you a picture and they will ask you that which nerve is injured and which side nerve is injured here. So, you have to say ipsilateral or contralateral deviation based on the rule of 17. Yeah. The tongue licks the wound. Yeah. No, to exactly the tongue licks the wound. Push effect. Yeah. Christian, right? Okay.

Now, the transverse section of the neck, guys. One of the, again, one of the famous questions asked. Now, in the transverse section of the neck, the knowledge of the deep cervical fascia is important to identify the spaces, number one, and number two, to identify the nerves inside. Now, first, look at the spaces, guys. If you look at the picture, this here is the pharynx, and the fascia that you see which is present just behind the pharynx, that fascia is the buccopharyngeal fascia. You all know the pharynx is covered with the buccopharyngeal fascia. Then, look at this fascia, guys, which is present in front of the vertebral column. In fact, it's not just in front of the vertebral column. It is covering all these prevertebral muscles. That's the prevertebral fascia. This fascia is prevertebral fascia, or in between the buccopharyngeal and prevertebral fascia, that's another fascia present over there called as the alar fascia. So, between the pharynx and the vertebral column, I hope you can appreciate the three fascias there. So, we have buccopharyngeal, we've got the alar fascia, and we've got the prevertebral fascia. Now, the space which is present between the buccopharyngeal fascia and the alar fascia, guys, that is called as the retropharyngeal space. This space is closed below. So, it's not dangerous. But the space present between the alar fascia and the prevertebral fascia is the dangerous space of the neck, one of the PYQs, guys. The reason we call it the dangerous space of the neck because this space is not obliterated below. So, this space of the neck continues into the posterior mediastinum, or a space diaphragmata. It goes to the diaphragm, guys. So, it opens below the diaphragm, and that's why the infection of the dangerous space of the neck can reach the posterior mediastinum. It can compress the esophagus, it can compress the trachea, can cause dysphagia and dyspnea also. So, that would say infection, abscess descends down into the posterior, and they can cause dysphagia and dyspnea. That's why it is called as a dangerous space of the neck. Okay. Okay.

That was the same picture again, but this time in this transverse section, we are not focusing on the fascia. We are focusing on the nerves inside here. Now, nerves, very important, guys. See, now, just I want you to focus, look at the image, and look at some circles which will come in here. Look at the first circle there, guys. Can you see a circle there? Now, that circle, that end circle over there, that's what I'm talking about. This circle here is basically present in the tracheoesophageal groove, between the trachea and esophagus. Look at the another circle which is present inside the carotid sheath. Look at another circle which is behind the carotid sheath, behind the carotid sheath, but in front of the prevertebral fascia, or between the carotid sheath and the prevertebral fascia. Between the carotid sheath and the prevertebral fascia. Another circle there which is behind the prevertebral fascia this time, but in front of the muscle, that is the scalenus anterior. Scalenus anterior muscle. And then finally, between the scalenus anterior and scalenus medius, there's another circle there here. So, look at these five circles that we have here, and let me start with the first. The first circle that you're looking at, guys, which is between the trachea and esophagus in the tracheoesophageal groove, the recurrent laryngeal nerve will be seen here. Tracheoesophageal groove may, whether it's an image-based question or they ask you like theoretically, the tracheoesophageal nerve to, you know, it's the recurrent laryngeal nerve. Then, look at the nerve which is inside the carotid sheath. The main nerve is the vagus nerve that is inside the carotid sheath. Then you have the nerve which is sandwiched between the carotid sheath and the prevertebral fascia. That is the sympathetic chain, between the carotid sheath and the prevertebral fascia. Then you see something which is behind the prevertebral fascia but in front of the scalenus anterior. Look at that. That is what? The phrenic nerve. Very important, guys, the phrenic nerve. It runs anterior to the scalenus anterior but posterior to the prevertebral fascia, or you can say between the prevertebral fascia and the scalenus anterior, which are present, that is the phrenic nerve. And finally, you will see the cervical nerves, C5, C6, C7, C8, all the cervical nerves which are going to form the roots of the brachial plexus, emerging between the scalenus anterior and scalenus medius. So, these are cervical nerves which are forming the roots of the brachial plexus, and they are the ones which emerge between the scalenus anterior and scalenus medius muscle. Muscle that is scalenus anterior, and this one is scalenus medius muscle. In between them, we have these cervical nerves which are going to form the brachial plexus. Yes, good answer, guys. Yeah, it's, it's good that you are answering simultaneously as well. So, in the transverse section of the neck, this is some, this is minimum that is expected from you to identify the retropharyngeal and the dangerous space of the neck, and make sure you identify every single nerve, especially nerves, guys, because what they will do, they will formulate a clinical question out of it. Question: there is a difficulty in breathing, that is because of which nerve? Of the phrenic nerve. To identify the phrenic nerve in that. There's a patient who's having, uh, the gut mobility is reduced because of vagus nerve involved. Vagus nerve that is inside the carotid sheath. The person is having difficulty in phonation because of recurrent laryngeal nerve. Recurrent in tracheoesophageal groove. So, the question might be clinical, but you might have to identify the nerve in the transverse section.

In this transverse section, one topic which needs special attention because that is asked separately in the exam and not like more than once is the carotid sheath. If I take the carotid sheath out of this picture, guys, and you'll notice one thing that when you look at the carotid sheath, the contents of the carotid sheath, we have common carotid artery, we've got internal jugular vein, we've got vagus nerve. That's the main, main structure present inside here. But is it the only thing present inside? Common carotid artery, internal carotid artery, internal jugular, and vagus nerve. Look at that. Even the ninth nerve, 11th nerve, and 12th nerve are partly present inside. These nerves are just crossing the carotid sheath. If this is my carotid sheath here, if a nerve is going to cross through it, it is a content only. Now, so even the ninth nerve, 11th nerve, and 12th nerve are also traversing the carotid in the upper part. So, they're also counted as content. The anterior relation of the carotid. What is the anterior relation, guys? Exactly adherent to the anterior wall of the carotid sheath is the ansa cervicalis. Look at the two dots over there. There is the ansa cervicalis which supplies the trapezius muscle. That ansa cervicalis is adherent to the anterior wall of the carotid sheath. Whereas, a posterior relation of the carotid sheath, we just saw what was the posterior relation, guys? Sympathetic chain. Sympathetic chain is forming the posterior relation of the carotid sheath here. So, the carotid sheath is something which is, which is asked, guys. First of all, the carotid sheath is an extension of different fascias. Investing layer, investing layer, pre-tracheal layer, prevertebral layer. All the major fascias together will give rise to the carotid sheath. So, carotid sheath is an extension of investing layer, pre-tracheal layer, prevertebral layer. Carotid sheath is enclosing common carotid artery, internal carotid, not external carotid, common carotid, internal carotid, jugular vein, internal jugular vein, and ninth and 11th, 12th. No, let me say ninth and 11th, 12th, no. So, 10th is the main nerve here. Anterior relation, posterior. Some authors even say ansa cervicalis as a content of the carotid sheath because ansa cervicalis is not just the anterior relation, it is adherent. It is submerged in the anterior wall of the carotid sheath. That is ansa cervicalis, which is supplying the strap muscles.

Another important point from this, from this deep cervical fascia that you should know about is a rule for the investing layer. Investing layer of deep cervical fascia follows a rule called as the rule of two. Now, when I say the rule of two, guys, rule of two that means the investing layer is enclosing two muscles, that is the sternocleidomastoid and the trapezius. It encloses two glands, that is the parotid gland and the submandibular gland. Remember, not thyroid gland. People do commit this mistake, guys. Thyroid gland is present in the pre-tracheal fascia. Please don't forget this. Thyroid gland is in the pre-tracheal fascia. It's the parotid gland and submandibular gland which are in the investing layer. Easy way: salivary glands. Salivary glands are inside the investing layer. Parotid gland and submandibular gland. The salivary glands are present inside the investing layer. Two glands. Two spaces. Investing layer is forming one space here that is called the suprasternal space, and it is forming one space above the clavicle here that is called the supraclavicular space here. So, we have two spaces also which are made up of this investing layer. Two ligaments: stylohyoid and sphenomandibular. The two ligaments which are all modifications of, of this investing layer. These are the two ligaments of the TMJ, temporomandibular joint. Stylohyoid, from styloid to mandible, and sphenomandibular, spine of sphenoid to the mandible, sphenomandibular ligament. And finally, the two pulleys. The two pulleys, guys, which muscle will need a pulley? The muscle which is having double belly, digastric muscle, omohyoid muscle are the muscles having two bellies. So, those two pulleys are also the pulley are also made up of the investing layer. So, rule of two: two muscles, two glands, two ligaments, two spaces, and two pulleys. They're all made up of investing layer of deep cervical fascia. They're all made up of deep cervical fascia. Exactly. Yeah. So, that was all the deep cervical fascia.

Now, into the dural venous sinuses, guys. I'm sure you read about the dural venous sinuses, but obviously, nothing is more important than the cavernous sinus. Now, it's the coronal section of the cavernous sinus you're looking at on the screen right now. Now, in the coronal section, you'll notice that there are nerves which are in the lateral wall of the cavernous sinus. And that nerve, in the sequence, we have a third nerve, we've got a fourth nerve, we've got the ophthalmic nerve, and we've got the maxillary nerve. So, these are the four nerves in the lateral wall of the cavernous sinus. Third, fourth, V1, and V2 in the lateral wall. In the lateral wall, the one nerve which is present inside the cavernous sinus along with the internal carotid artery is the sixth nerve, guys. Sixth nerve and internal carotid artery is inside the cavernous sinus. If the question is asked to you that which nerve is most commonly affected in the cavernous sinus thrombosis, to obviously the sixth nerve. The nerve which is, the nerve which is inside the carotid sheath is the, inside the cavernous sinus, that is the, that is the abducent nerve. Sixth nerve is the one which is basically most commonly affected in this cavernous sinus thrombosis here. Even the internal carotid artery present inside the cavernous sinus is an issue. I mean, it's an advantage also because it dampens the pulsation, but it's a problem also because if there is an aneurysm of the internal carotid artery and that is ruptured, so there is a formation of fistula called as a carotid-cavernous fistula. Because of this carotid-cavernous fistula, what will happen? The blood of the internal carotid artery is filled inside the cavernous sinus, and every time the internal carotid artery will pulsate, the entire cavernous sinus will also pulsate, and that is going to push the contents of the orbit also, causing pulsatile proptosis also, guys. You can see that picture over there. You can see that, that, that's the, that's the blood of the internal carotid artery filling inside the cavernous sinus. You can see over there, right? That's the one, right? And that is a carotid-cavernous fistula. And carotid-cavernous fistula gives origin to this. Can you see this pulsating eyeball? That's a pulsating proptosis or pulsatile proptosis. That is an indication. If you see it's not pulsating, it's not exophthalmos. The eyeball looks normal. It's a pulsatile proptosis. So, if you see the eyeball is pulsating, that's an indication that this person's internal carotid artery might have ruptured inside the cavernous sinus, which is pushing the contents of the orbit as well. Exactly.

Moving on. Now, coming to muscles of mastication in head, neck, and face. Again, if, if, if you have to again, you know, kind of categorize the topic, there are many topics which look very important, but muscles of mastication definitely wins the race, guys. Muscles of mastication, to whether it's in NEET or AIIMS exam, out of all the muscles in the human body, from the anatomy point of view, the most commonly asked muscles are the muscles of mastication. So, obviously, you've got to do them carefully. Now, the muscles of mastication, you always have to orient the muscle how it is running toward the mandible. Like the muscle that you're looking at right now on the screen, that is the temporalis muscle. Muscle temporalis muscle, coming from the temporal fossa, and you can see this muscle is converging toward the coronoid process, guys. That process where it is inserting is the coronoid process. So, when the temporalis muscle will contract, it is going to elevate the mandible, one. It is going to lift the mandible up. So, it is one function is elevation, and it is going to pull the mandible back also, that is retraction. And that's the two functions of temporalis muscle: elevation and retraction. Elevation is a strong function of this temporalis muscle, but the unique function of the muscle is what? Retraction. There is no other muscle of mastication which can cause retraction. A temporalis which can pull the mandible back. Retraction is a unique action of the temporalis muscle. The next muscle over there is the masseter. Now, if you look at the masseter muscle, present on the outside, again, the insertion is always on the mandible, guys. It is inserted on the mandible. So, when, when, when you touch this mandible on the side, you clench your teeth, when you touch on the side, this muscle on the side is masseter only. So, this masseter muscle, the strongest muscle of mastication, when it contracts, its main job is to elevate the mandible. It slightly protrudes the mandible as well, but the major action of the masseter muscle is elevation. It's the strongest muscle of mastication. You can again see the direction is upwards. The muscle is going to pull the mandible in the upward direction. It's the main muscle for elevation. If I remove this muscle, I will see mandible. If I remove the mandible, I will see one muscle inside which is oriented in the same way only, just like this masseter muscle, and the name also starts with M. That is the medial pterygoid muscle. Look at the guys, muscle medial pterygoid. This muscle inside, that's the medial pterygoid muscle here, right? That's another one, the lateral pterygoid. So, medial pterygoid muscle is oriented the way the masseter muscle is, and that's why the action of medial pterygoid muscle is also like masseter, that is also mainly for the elevation. Both masseter and medial pterygoid muscle, they can help in protrusion as well, but the main action is the elevation. And then we have the finally, the most important muscle out of all the muscles of mastication, this wins the race, guys. The maximum time the question asked is on the lateral pterygoid. The lateral pterygoid muscle is running backwards. If you look at the, the, the biomechanics of this muscle, when it contracts, it, it pulls the mandible forward. So, it's a muscle for protraction, and it's the only muscle which is going to pull the mandible downward. It is going for depression. The unique action: protraction and depression. Protraction and depression is the action of lateral pterygoid muscle. It's the major protractor, main protractor. Okay. And the depressor, that there's no other muscle which can cause depression. Protraction can be done by the masseter also and medial pterygoid also partly, but depression muscle. So, unique thing about this muscle is depression here, right? Depression is the main action and the unique action of this muscle here. So, if they ask you these muscles individually, that is, have to you have to deal with it. If you try to mug up these muscles, you'll forget them. Try to look at the direction of the muscle fibers and based on that, you can answer it here. So, look at the, like, make a picture in your head how temporalis muscle is oriented. Masseter and medial pterygoid muscle are both in the same direction. One is outside, one is inside the mandible. And lateral pterygoid is going backward. So, it is going to protrude the mandible and open the jaw. It is going to open the jaw. The most common dislocation of the mandible, I hope you know, that's an anterior dislocation. And anterior dislocation can be because of excessive opening of mouth, like yawning. Yawning may you can, it can lead to the anterior dislocation.

Now, another one more topic that I need to tell you from the head and neck, which is from the exam point of view, is important in the triangles of the neck. It's the posterior triangle, and something very specific in the posterior triangle I want to tell you, guys, here. The, in the posterior triangle, the muscle in the posterior triangle, I hope you know that that muscle over there is the sternocleidomastoid muscle, right? This muscle is the trapezius muscle, and the muscle which is dividing the posterior triangle, that, that muscle over there is the inferior belly of the omohyoid. Now, there is one nerve that you see which is emerging from the posterior border of the sternocleidomastoid, and this nerve is going to run along over the sternocleidomastoid, going above. And this important nerve is the great auricular nerve. Very, very important question, great auricular nerve. Why is the great auricular nerve important, guys? Great auricular nerve is the root value C2 and C3. There are a couple of branches for this great auricular nerve. There are multiple questions asked in the recent past, and they all belong to the great auricular nerve. Now, look, first of all, the nerve, great auricular nerve, it goes above, and I told you the root is C2, C3. This great auricular nerve runs along with the external jugular vein. That's a neat question, guys. Which nerve runs on the side of the neck along with the external jugular vein? So, if you're doing any intervention on the external jugular vein, you've got to be careful for what nerve. Great auricular nerve can get injured. Number two, this nerve supplies the lobule of the ear. This nerve supplies the angle of the mandible, and it also supplies the, the skin, this parotid area skin, which is also called as the shaving area. It is a recent surgery question also that the patient had a sensory loss which he felt while doing the shaving. So, which nerve was injured in the parotid surgery? Great auricular nerve, because it supplies the lobule of the ear. It supplies the skin at the angle of the mandible and this parotid region, which is basically the shaving area here. Like in the shaving area also, the great auricular nerve is important because, guys, in parotid surgery, I'm sure you all know, in parotid surgery, the auriculotemporal nerve commonly injured. If the auriculotemporal nerve is injured, that regenerating auriculotemporal nerve is likely to fuse. Regenerating auriculotemporal nerve is likely to fuse with the great auricular nerve. It is very likely to fuse with the great auricular nerve. That is, the auriculotemporal nerve can fuse with other nerves also, like the buccal nerve, lesser occipital nerve, but most commonly, the auriculotemporal nerve fuses with the great auricular nerve. That's why the patient can be seen sweating in this area, on the parotid area, in Frey's syndrome here, right? And this is something I told you that injury to the parotid surgery, sensory loss in the shaving area. Parotid is shaving. That, that's how the question was asked here. So, all the points that is written in front of you, they're all asked as separate questions: runs with external jugular vein, supplies the lobule of the ear, supplies the angle of the mandible, parotid region, Frey's syndrome, sensory loss in the shaving area. Question: exam already, or sub-answer that is great auricular. You can see how commonly this question is asked here. So, that's a nerve which is basically present in the roof here.

The another important structure that I need to tell you in the posterior triangle is the spinal accessory nerve, and I wanted to look at the screen that how the nerve is running, guys. Nerve actually comes from anterior to posterior. Look at that. If you look at the nerve running from anterior to posterior, that's the spinal accessory nerve. So, spinal accessory nerve basically supplies the sternocleidomastoid. First, first, it supplies sternocleidomastoid, then it supplies trapezius muscle. And that's the catch, because spinal accessory nerve is running in the neck quite superficially in the posterior triangle. So, it is, it is kind of like, it, it gets injured in this way. If the spinal accessory nerve, it runs between the investing layer and prevertebral layer. It is running between the investing and prevertebral. That's why it's very superficially placed. If the spinal accessory nerve is injured in the posterior triangle, the problem is the trapezius muscle will get affected, but not sternocleidomastoid. Sternocleidomastoid muscle will be spared. Sternocleidomastoid supply muscle is already supplied by the nerve, and then it enters into this triangle. So, if the nerve is injured in the posterior triangle, always remember that the patient will not have any loss to the sternocleidomastoid. We'll only have the function of trapezius muscle affected. And what are the functions of trapezius muscle which are affected? The patient will have difficulty in shrugging of the shoulder, difficulty in retraction of the scapula, difficulty in overhead abduction, and to some level, it will be winging of the scapula also, but mainly the trapezius is affected, and that will cause all these, guys. It will cause difficulty in shrugging, difficulty in retraction of the scapula, difficulty in overhead abduction. So, only trapezius functions are affected, but not sternocleidomastoid muscle will be spared. So, that is in the posterior. There is, there's, there are too many things in the posterior triangle, guys. We have, we have trunks of brachial plexus, subclavian vessels, but again, as I said, my job is to kind of filter the information, give it to you from the exam point of view. When the question is asked on the posterior triangle, I can vouch for it, their favorite, favorite question to ask is either great auricular nerve, mainly great auricular nerve, in fact, I would say, or the question on the spinal accessory nerve. And this has been repeated like from the last 10, 15 years, they've been asking questions on these two nerves repeatedly over and over. Okay. Yeah. Okay.

Again, cranial fossae, guys. I, I believe that you people have read about the cranial fossae. You read about the different foramina here. But again, I have to, I need to focus on the most important foramina in this picture, and the two foramina which are again asked in the recent time as well. One of them is the foramen lacerum. Now, if you look carefully, this foramen lacerum is not a foramen in any bone. It is a space left between the bones. Yellow colored bone there is the sphenoid bone. The green colored is the petrous temporal. The blue one is the occipital bone. So, different bones are surrounding this here. So, this foramen here is called as the foramen lacerum. And this foramen lacerum is surrounded by, look at the multiple bones. We have sphenoid bone, greater wing of sphenoid, body of sphenoid. We have petrous temporal, apex of petrous temporal, and we have an occipital bone, basal part of occipital. So, simply name the name, name of the bone only: sphenoid, temporal, petrous temporal, in fact, and occipital bone, that is the one which is surrounding this. The foramen lacerum is an interesting foramen because there are some structures which are just traversing the foramen lacerum, they are just traversing it, like, like passing through and through, and some structures are coming from somewhere else and just running through it here. So, they are not the true content. So, in the foramen lacerum, guys, there are two types of content. Now, when I say traversing foramen lacerum, the major content of foramen lacerum, so we have some, you know, meningeal branches of ascending pharyngeal artery, an artery which is supplying the dura mater, and some emissary vein is there. The structures which sound not very important are the actual main content of the foramen lacerum. Apart from that, we have greater petrosal nerve, internal carotid artery, lesser petrosal nerve, sympathetic plexus. All these structures are present inside the foramen lacerum, but they're just filling it up. They fill up, they are not the actual. If this is foramen lacerum, something passing through foramen lacerum is something which is traversing it, but structures like this and then goes into foramen lacerum, that's just filling it up. It's not the main content. Overall, these are the contents of foramen lacerum, but if they ask you the question like what structures are traversing foramen lacerum, then you only have to go with this artery and the emissary vein, and not all these.

The another important foramen is the jugular foramen, guys. Now, this jugular foramen again is present between two bones. Look at the green and blue over there. We have petrous temporal and occipital bone. So, jugular foramen is also present between the two bones, that is, occipital bone and petrous temporal. Jugular foramen, the most anterior, if, if I just take it out, the most anterior and the posterior part of the jugular foramen is having the two sinuses which together will give rise to the internal jugular vein. So, we have a sinus called as the inferior petrosal sinus, and then we have a sigmoid sinus. That is inferior petrosal and sigmoid sinus, and both these sinuses come out of the jugular foramen, and immediately below the jugular foramen, they join to each other to form the internal jugular vein. So, a question can be that these are the two formative tributaries of the internal jugular vein. When these two sinuses unite together, they give rise to the internal jugular vein. The nerves which are present between, in the foramen lacerum, in the sequence from anterior to posterior, we have the ninth nerve, 10th nerve, and 11th nerve. We have the ninth nerve, 10th nerve, and 11th nerve. And in the ninth, 10th, and 11th nerve, one and, and some arteries, some meningeal branches of ascending pharyngeal arteries are also there. They're not very important. So, the important thing is, guys, 10th and 11th nerve. Can you see a dotted line present around them? And ninth is having a separate dotted line over there. Look at that circle, moving circle over there. That's a, that was a question asked here. Ninth nerve. Ninth nerve is the one which is having a separate passage. Passes through jugular foramen. There is a separate passage for the ninth nerve to pass through it because there is a separate dural sheath for it. 11th nerve and 10th nerve, they have a common dural sheath because 10th and 11th nerve, they obviously both going to join together and they will form the vagus-accessory complex. So, that's why 10th and 11th nerve, they have the same, same, what do you say, uh, dural sheath, and ninth nerve is the one which is having a separate dural sheath. Is there? Ninth nerve is having a separate dural sheath here. That, that's why the ninth question was asked. The question was something like this, that which content present in jugular foramen is having a separate passage? Jugular foramen, maybe, but still separate passage, and that is the ninth nerve over there, right? So, these are the two most important foramina that, that I, you should know about, that is the, that is the ninth nerve is the structure which is passing separately through it.

Now, this picture, guys, if you're looking at a picture like this where you are looking at the cranial fossae, and in this cranial fossa, if you, if you look at that box over there, it is showing you some cranial nerves inside. I would, I, I believe that this question probably will not be asked in the NEET exam. It's more of an AIIMS type of question when they can give you a picture of the cranial fossa, but with the dura mater intact. If the dura mater is intact, it's a little difficult to identify the nerves. So, we've got to go with certain hints over there. Like, if you look at this in the anterior cranial fossa, you can see there's a projection coming from the anterior cranial fossa toward the posterior side, toward the middle cranial fossa. That is called as the anterior clinoid process. If you see a nerve, is this picture? Cavernous sinus will be somewhere here. This is where the cavernous sinus will, like, it's, it's just roughly, that is, that is the place of the cavernous sinus there. Now, this nerve over there, it's the optic nerve. That is, nerve that is, the optic nerve is there. Optic canal is present just medial to the anterior, anterior clinoid process. Immediately, that is the optic canal. So, optic nerve is there. The nerves which we already discussed, present in the lateral wall of cavernous sinus, is the third nerve, fourth nerve. Look at the thin nerve over there, fourth nerve, and we have the fifth nerve. Now, I cannot see the parts of the fifth nerve. I can just see the trunk of the fifth nerve over there. So, look at the fourth nerve, especially. Let me enlarge this for you, guys. Look at the third nerve there, and this thin thread-like nerve, the thinnest cranial nerve, the fourth nerve, and the fifth nerve. These, these nerves are present more toward the lateral side, in the lateral wall of cavernous sinus. The only nerve which entered the cavernous sinus was the sixth nerve, abducent nerve, and the reason it entered the cavernous sinus because it is coming from the posterior side, and that is one of the nerves asked in the exam. This is the abducent nerve. Don't look for the abducent nerve on the lateral side. Look at behind the cavernous sinus region. That's the sixth nerve, guys. That abducent nerve or sixth nerve is there, right? That's the only nerve that you see on this clivus. Clivus is the slope. That is the sixth nerve, abducent, in the posterior cranial fossa. This is where we have the internal acoustic meatus. This is where we have the jugular foramen, and further below, we have this hypoglossal canal. And that's how you can make out the content. If it is an internal acoustic meatus region there, that means it is going to give passage to the seventh and seventh and eighth nerve. If this is a jugular foramen, we just saw it is going to give rise to the ninth and 11th nerve. And further below, you can see some rootlets of the hypoglossal nerve are present there. So, in the sequence, you'll find them in the posterior cranial fossa. You may see a tough nerve above, then further below, then further below. That is, we have the sixth and seventh nerve, uh, seventh and eighth nerve, I'm sorry, that is from internal acoustic meatus. Ninth and 11th nerve from the jugular foramen, and hypoglossal nerve rootlets can also be seen that is present over there. So, that's how you're going to identify the nerve if the dura mater is intact. Look for the anterior clinoid process, this clinoid process. The nerve medial to the clinoid process is the optic nerve. The nerves in the lateral wall of cavernous sinus are three, four, and five nerve. The nerve which is present behind the cavernous sinus, through the clivus, is the sixth nerve. And then in the posterior cranial fossa, look for internal acoustic meatus, jugular foramen, and the hypoglossal canal. I mean, in the sequence, you can find out the nerves are running in there if the dura mater is intact. Okay, guys.

Moving on. Now, I'm sure that the moment you look at this picture, we all know that this, how many times this question is being asked, and they are still not stopping. Pterion. Pterion is this point, obviously, which is on the, this H-shaped suture is on the pterion on the side of the skull. When I say pterion, guys, the four bones which are contributing to the pterion are, we have this, that is the frontal bone, of course, that's the frontal bone contributing to the pterion. We've got this parietal bone, that's an easy one. And the next two bones, you need to be very specific here. This is, we have the squamous part of the temporal bone. First of all, it's not the petrous part, the squamous part of the temporal bone, and the greater wing of the sphenoid here. So, please make sure that for the temporal bone and the sphenoid bone, remember what part is that? That's the squamous temporal, and we have the greater wing of the sphenoid. Okay. Pterion is important. And here, the thinnest part of the skull bone, actually, easily fractured also. Any blow to the skull on the side, the pterion can get fractured, and there are many structures present inside which can get involved. So, what are the structures which are lying deep to the pterion? Well, we all know, guys, if this is the skull, and you can see the brain is shown like deep to it here now, and that is somewhere the pterion is present, like, just roughly. Middle meningeal artery. We all know that the middle meningeal artery is having two divisions. It's the anterior division of the middle meningeal artery which will be seen over there. So, look, relation may, can we add? See superficial temporal vessels. This is a very recent question. Generally, we think about the deeper relation. There's one relation outside also. Superficial temporal vessels are there. Now, if I go inside the pterion, you will see the anterior division of the middle meningeal artery. This sulcus here is the Sylvian sulcus or Sylvian fissure. Middle cerebral artery passes through it. If I go further more deep, then I'll see middle cerebral artery or middle cerebral vessels are there. This fissure, where the middle cerebral artery is present, is called as the Sylvian fissure. Insula, you know that the Sylvian fissure, if, if you open the Sylvian sulcus or lateral sulcus, hidden lobe of the brain can be seen. So, insula. And if a person on the left, left side, I mean, this, this is the right side here, on the left side, the deep to the pterion, because the inferior frontal gyrus is also having Broca's area. So, even Broca's area is in relation. Main relation is the anterior division of the middle meningeal artery. No doubt about that. Middle meningeal artery is the main relation to the pterion. But question, we should know all the relations for the pterion here. So, superficial temporal vessels are outside. Middle meningeal artery. You go further inside, you'll see middle cerebral artery. Further inside is Sylvian fissure. More inside is insula, and even the Broca's area on the left side is also in relation to the pterion. So, all these structures, all these areas can be, can be approached taking this, the pterion route. Yeah.

Well, this, I'm sure that you must have discussed this with Dr. Rohjat in detail about the extradural hemorrhage. Any rupture, any fracture of the pterion can lead to the rupture of the anterior division of the middle meningeal artery, causing the extradural hemorrhage. So, followed by this, some, some of the topics of head and neck, again, we come back to some of the, some of the topics from the histology. And this is something which I have taken from my own will because in the entire GI slide, I'm not expecting you to sit down and read every slide of GI. I feel this is important because a slide of a duodenum. What makes a duodenum slide important, guys? Duodenum is one slide in which you will see these glands. You will see in duodenum villi, which are having these goblet cells and columnar epithelium, and microvilli will be there. That you will see in the jejunum also. Also, to I say, though I don't think that you will be able to differentiate between duodenum, jejunum, and that's not easy. What makes the duodenum very important and very specific is the presence of these Brunner's glands. Now, look at this Brunner's gland. This mucosa, they are present in submucosa. Generally, glands, mucosa, submucosal intestinal glands, submucosal, submucosal glands. The two slides which are having the glands in submucosa, one is esophagus. Esophageal glands are also in submucosa, mucosal glands are there, and even Brunner's gland in the duodenum are also in the submucosa. So, that's the main reason I want to just show you this picture here. You're looking at the villi. The moment you look at the villi, obviously GI slide, GI slide, is it, is it jejunum? Is it duodenum? Duodenum is easy to identify. Duodenum, you're looking at the glands which are present in the submucosa, guys. Can you see the muscularis mucosa over there? That is the muscularis mucosa there. And if this is the muscularis mucosa, deep to that is what? Submucosa. And you have the Brunner's gland in submucosa. Had it been the slide of the stomach or the slide of the jejunum or slide of the other part of the intestine, then you will see the intestinal glands present only in the mucosa, not in the submucosa.

Thyroid follicle. Very simple slide, but because it is asked on the exam, so I, I have to give it to you, guys. That, that is the thyroid follicles. You're looking at. When you look at the thyroid follicle, you can clearly see these cuboidal cells or columnar cells could be there. Cuboidal to columnar cells can be seen. Cuboidal is a better answer. Choose what is simple. Cuboidal is a better answer. That the thyroid follicles are lined with. Then inside, you can see the colloid, and these colloid is having a serrated border are there, guys. That it's an active thyroid gland. Looking at. And we have a serrated border of this, of this colloid. And what is also to be noted that between these, these thyroid follicles, we have these cells. Look at these cells, guys, in between here. These are the parafollicular cells. The same parafollicular cells which are derived from the neural crest cells, which are migrating into the pharyngeal arches into ultimobranchial bodies. So, these parafollicular cells, the large cells, and they are poorly staining. So, basically, it's pretty easy to identify if you're looking at thyroid follicles and thyroid. So, these are larger cells, the big nucleus is there, and they are basically poorly stained compared to the follicular cells. They are the, the parafollicular cells will be there, right? So, the thyroid follicle slide is there.

Now, one slide which is not asked in the recent time, but you know, sometime we have to kind of anticipate certain things, and and this is what I anticipate, guys. This is not the slide to which is asked in the recent, recent time. It's, it's a never in the image-based question yet, but I feel that adenohypophysis, anterior pituitary slide are important. Anterior pituitary slide is important because the staining are very, very clear, and you can see the three types of stain over there. You can see acidophils, you can see basophils, and you can even see chromophobes, the cells which are poorly stained, right? Okay. So, if I say in the anti, adenohypophysis, if I talk about the acidophils, you know acidophils, I mean, you read this all in physiology and pathology and and medicine very well. So, I don't have to go into that. See this about the acidophils, they stain red in color. Somatotropes and lactotropes. The question could be, they might give you a slide like this and they will ask you about the, the, the hormone which is being secreted by those cells here. The acidophils are the somatotropes and lactotropes. If it is a blue stained cell, you can see the stained blue basophil cells. We have thyrotropes, gonadotropes, and corticotropes are there. That is from the basophils. And then look at this, especially I'm just putting this arrow over there. It is neither acidophil nor basophil. It's a chromophobe. Pale cells are there. Maybe inactive or in transition. We don't know much about the chromophobe cells here, but the chromophobes are also to be seen over there. Now, again, this is a slide which I have given to you because looking at their, in the recent time, they have given some gland slides, and this is the gland they have never given, and this could be a good question to formulate also, you know, self-mark maybe acidophil, and they will ask, okay, which hormone is secreted from this? So, they will give TSH, GH, or any other. You have to go with the GH over there. It's a somato, which is coming, uh, somatotropes cells are there, which are acidophils, right? So, identify the acidophils, basophils, and chromophobes, and I hope that you already read about this in endocrine, in, in more detail. I, I'll share this PDF. Don't worry about the PDF. It's all yours. Just, just immediately after the slide, the first thing I'm going to do is I'm going to send this slide, uh, to the, to the moderator, and he will, he will share the slides with you, with you all. Don't worry about that.

Ch sir, let's move on to the next major unit that is neuroanatomy. Now, neuro, guys, in the neuroanatomy, uh, I mean, again, as I said, we have to just filter out the information and look at the major part from where usually the questions are being asked. Although I believe that neuro is something that if you would have read, I mean, INI is too close, but for the NEET exam, I would say that if you have not read neuroanatomy, investing one day for the neuroanatomy is not bad. I mean, and you're just relying on the one shot or like just only what is important in this. I would say neuro, if you read this in more detail, that will be beneficial, not only in the NT part, from the other, other, other medicine part, and physiology part as well. So, neuro, if you, whatever time you'll invest looking at that, one exam is very close, and then then we have a NEET exam, we have some, some, some more time in between. So, you know, I would say that it's a time, it's, it's a topic which is worth investing time. And though we'll be talking about some important topics in there, like, first of all, like the squeeze of the entire spinal cord, and that is Brown-Séquard syndrome. If you know the Brown-Séquard syndrome, that means you know the tracts, say, guys. In the spinal cord, we know that we have dorsal column tract. If I just, just very quickly clarify to you, let's say this patient is having a Brown-Séquard syndrome. Whichever level the Brown-Séquard syndrome is present, whatever level there is ipsilateral loss of all sensory modality at the level of lesion, just below the level of injury. Let's say there is an injury at the level of T6. So, at the level of T6, every single modality is gone: pain, temperature, touch, pressure, crude touch, or fine touch, or vibration, or stereognosis. Everything will be gone at the level of lesion. So, ipsilateral loss of all sensation only at the, at the level, at the level of lesion. There will be just, just hold on for this one. There will be ipsilateral loss of vibratory sensation and position sense because dorsal column tract runs on the same side only, guys. Dorsal column tract runs on the same side. If the dorsal column tract is running on the same side, so injury will have an ipsilateral effect, and dorsal column tract is responsible for this vibration and the position proprioception. Contralateral loss of pain and temperature below the level of lesion. Why? Because spinothalamic tracts, they cross over, and because spinothalamic tract will cross over and will go above. So, any injury to the spinothalamic tract, left side spinothalamic tract injured, to right side pain and temperature. So, contralateral loss of pain and temperature below the level of lesion. So, exactly, just at the level, exactly at the level of lesion, everything is gone. But if I talk about the bigger picture below the level of lesion, first of all, you will see ipsilateral loss of vibration, ipsilateral loss of position sense, because of dorsal column tract. Contralateral loss of pain and temperature because of what tract? Spinothalamic tract, especially mainly because of lateral spinothalamic tract involvement. And something which is very important to understand, paralysis, guys. Let's say this is a spinal cord here, the rough section of spinal cord. We all know that the lateral corticospinal tract will decussate. That's how the lateral corticospinal tract will decussate in the medulla oblongata. It will decussate in the medulla oblongata, and these fibers will now come into the spinal cord. That is the upper motor neuron. And from the spinal cord, the lower motor neurons will come out like that's a lower motor neurons, all coming out there. These are all lower motor neurons. Let's say this patient is having a Brown-Séquard syndrome at this particular level. Look at this flashing.

Light over there. This is where the Brown-Séquard syndrome is. No, just level pain at whatever level the Brown-Séquard syndrome has occurred at that particular level. Lower motor neurons are injured, and that's why this patient will have an ipsilateral flaccid paralysis at the level of the lesion. Ipsilateral flaccid paralysis at the level of the lesion because lower motor neurons are injured, but the rest of the lower motor neurons are fine; they're working, no problem. But their upper motor neuron is affected here. Or, upper motor neuron injury to there will be paralysis below the level of the lesion. Ipsilateral paralysis below the level of the lesion that confines the entire Brown-Séquard syndrome.

A patient with Brown-Séquard syndrome will have an ipsilateral loss of position sense, ipsilateral loss of vibratory sense, and contralateral loss of pain and temperature. Ipsilateral flaccid paralysis at the lesion and ipsilateral we have the paralysis below the level of the lesion. Yeah, below the level of the lesion. So, the question about Brown-Séquard syndrome is all about ipsilateral and contralateral. If you people have read about the spinothalamic tract, dorsal column tract, spinocerebellar tract, it's not a problem. But presuming that if you haven't read them or if you forgot about these tracts, at least remember these features: which one is ipsilateral, which one is contralateral. The simple one, simple way is pain and temperature contralateral. Just keep that pain and temperature is contralateral. Everything else is ipsilateral, ipsilateral, ipsilateral, ipsilateral, ipsilateral, and you still will be able to mark the right answer.

Okay, there's a picture showing the ventral aspect of the brainstem. Now, in the ventral aspect of the brainstem, guys, uh, you're looking at this, this, this area is the midbrain area. Look at this. This is the midbrain area, that is the pons here, and that is the medulla oblongata. Now, if you look at the midbrain area, this space between the two peduncles of the midbrain, that is, that is the crus cerebri. It is also called the cerebral peduncle. We have an interpeduncular fossa in between, and the nerve coming out from the interpeduncular fossa is the third nerve. Look at the third nerve from the interpeduncular fossa. The fourth is the only cranial nerve which is coming from the dorsal aspect here, the nerve which is coming from the posterior side, the dorsal aspect of the brainstem, that is the fourth nerve, the trochlear nerve.

The pons is huge, guys. The pons is huge. But the only nerve that you see emerging from the ventral surface of the pons is the thickest cranial nerve, and that is the trigeminal nerve. The trigeminal is the only cranial nerve emerging from the ventral surface of the pons because the nerves sixth, seventh, and eighth are coming from the pontomedullary junction. Okay. The sixth nerve, then we have the seventh nerve, both, both are seventh. It's a mixed nerve. So, part of, and then we wait. Now, sixth, seventh, and eighth nerves coming from the pontomedullary junction. So, not from the pons, pontomedullary junction, they leave the brainstem from the pontomedullary junction from medial to lateral: sixth, seventh, eighth. In the medulla oblongata, there are two major elevations that you have. One elevation here, this is the pyramid, guys, that's the pyramid, and that is the olive. Pyramid and olive. If you look at the nerve which is lateral to the olive, lateral to the olive, present posterolateral to the olive, we have the ninth, tenth, eleventh nerve. Ninth, tenth, eleventh nerve that emerges lateral to the olive. And the twelfth is the only nerve which is coming out between the pyramid and the olive. The emergence of the cranial nerves is very, very important when you're looking at the ventral aspect of the brainstem to know how cranial nerves are coming out. Third nerve from the interpeduncular fossa. Fourth nerve is the only nerve coming from the dorsal aspect of the brainstem. Then we have the fifth nerve, the only nerve emerging from the ventral surface of the pons. Sixth, seventh, and eighth nerves from what junction? Pontomedullary junction. Ninth, tenth, and eleventh nerves, they are coming from lateral or posterolateral to the olive. And the twelfth nerve, hypoglossal nerve, is emerging between the pyramid and the olive. Pyramid, that is the tenth.

Okay. Then the dorsal aspect of the brainstem, guys. We're looking at the brainstem from the front. Let's turn it around, guys. When you look at the dorsal aspect of the brainstem, the first thing you'll notice above is the superior colliculus, inferior colliculus. So, we have two superior colliculi and two inferior colliculi. And all the colliculi together are called the corpora quadrigemina. The four gem-like structures, we call them corpora quadrigemina. Just below the inferior colliculus, you can see the only cranial nerve which is coming from the dorsal aspect of the brainstem. What nerve was that, guys? That's the fourth nerve. Look at the fourth nerve over there. So, when you're looking at the dorsal surface of the brainstem, and there is a fourth nerve emerging from there.

Now, in the floor of the fourth ventricle, there are many structures present over there. But I'll tell you, if it is a cadaveric image-based question, they are going to ask you this: that is the facial colliculus. What is facial colliculus? Facial colliculus is the sixth nucleus present deep to it. That is the facial colliculus, and the facial nerve is winding around it. Internal genu of the facial nerve. When the sixth nucleus is present in the pons, and you will see the facial nerve winding around the sixth nucleus and emerging out, and that is called the facial colliculus, guys. Facial colliculus is there. Just below the facial colliculus, we have the hypoglossal triangle, vagal triangle. But I tell you honestly, in the image-based cadaveric picture, I'm very sure that they will not ask you where is the hypoglossal triangle, vagal triangle. It's not that easy to identify them. Facial colliculus is very easily appreciated here. We do have the vestibular triangle also.

Now, one question here is that which cranial nerves are seen in the floor of the fourth ventricle? Facial colliculus, deep consonant nucleus, sixth nucleus, deep to the facial colliculus, vestibular is eighth, hypoglossal is twelfth, and trigeminal sense. So, the nerves which are present deep to the floor of the fourth ventricle, we have sixth, eighth, tenth, and twelfth. Sixth, eighth, tenth, and twelfth. But what makes the facial colliculus so important? In the facial colliculus, we have this abducens nucleus, which is surrounded by the seventh nerve. So, any injury to the facial colliculus, the first structure to get involved is the facial nerve nucleus. So, if the question says there is an injury to the facial colliculus, or there is an injury to the structure producing the facial colliculus, always think about injury to the facial nerve because the nerve is present around the nucleus. So, the facial nerve will get affected first, and that's why the muscles of facial expression might be showing you the features in that case. The sixth nucleus may or may not get affected because it is present deep to the nerve here. So, that's the facial colliculus. Look at this, guys. This is the picture showing here. Look at what it shows. You can see the facial nerve is there, and that is winding around the sixth nucleus and coming out here. So, any injury to the facial colliculus on the dorsal side, if there is any injury to the facial colliculus from the dorsal side, the facial nerve will get affected, right? That's the facial colliculus. So, if the question says which cranial nerve nuclei are present in the floor of the fourth ventricle, so we have sixth, eighth, tenth, and twelfth nuclei. But obviously, the injury to the facial colliculus, I told you, abducens nucleus surrounded by the lower motor neuron of the facial nerve. Any injury to this facial colliculus, there will be a lower motor neuron lesion of the facial nerve. Injury is the first thing you have to think about. Because I know that they will keep on twisting this question over and over again, but do not deviate from your answer unless the examiner says there is an injury to the nucleus present deep to the facial colliculus. Never go with sixth as an answer. Injury to the facial colliculus, injury to the structure producing the facial colliculus, injury to this bump that you see in the floor of the fourth ventricle, it's mainly the injury to the facial nerve. What's cereal? Don't worry. Okay. Yeah.

So, sagittal section, guys. Three sections of the brain are immensely important. Now, look at this green highlighted area, this flickering area, the green area, that's the third ventricle. So, when you see a sagittal section, the third ventricle in the picture like this, it's very important for you to identify the structure. The question could be very simple, the question could be about connections, question could be about something else, but if you don't identify the structure, then you will not be able to answer it. If you look at the third ventricle, the roof of the third ventricle is made of this white matter bundle, which I'll talk about separately, also called the fornix. The fornix, the body of the fornix is there, and just below the fornix, there we have the choroid plexus. So, the body of the fornix and choroid plexus are present there, that is forming the roof of the third ventricle.

Anterior wall of the third ventricle is by, let me go to the posterior. According to this PowerPoint, posterior side of the ventricle, we have the pineal gland. So, what I was saying that it is a pineal gland. There, above the pineal gland and below the pineal gland, we have the habenular commissure above, and we have a commissure which is present below, called the posterior commissure. And just below the posterior commissure, I hope you can even appreciate this aqueduct of Sylvius there. Look at that duct over there, which is leading into the fourth ventricle, that is the aqueduct of Sylvius. So, these four structures are forming the posterior wall of the third ventricle in sequence. Nowadays, the examiner is very interested in asking this question: arrange them in sequence. So, habenular commissure, pineal gland, posterior commissure, aqueduct – the four structures forming the posterior wall of the third ventricle.

Anterior wall of the third ventricle is by the commissure, another small commissure, that is called the anterior commissure, and the lamina terminalis. Lamina terminalis is important embryologically also because lamina terminalis indicates the closure of the cranial neuropore. The neural tube, guys, the neural tube, to it forms the lamina terminalis, cranial neuropore. When it closes, cranial neuropore closes on day 25. On the 25th day, when the cranial neuropore is closed, eventually the brain can, the structure which represents that closure of the cranial neuropore is this lamina terminalis. Lamina terminalis is the cranialmost end of the neural tube, closing, closing of the cranial neuropore. Yeah. And then comes the floor. I'll tell you something interesting here. The floor of the third ventricle has something to do with the ventral aspect of the brainstem. Just, just give me one second. If my image may just very quickly take you back to this picture. Yeah, look at that, guys. Have a look at this here. If you look at the ventral aspect of the brainstem, can you see the optic chiasm there? Just look at the circle there. Optic chiasm, that is the infundibulum of the pituitary. This, there we have the mammillary bodies, and then we have the posterior perforated substance. Look at these structures in the sequence here. Optic chiasm, there is the infundibulum of the pituitary. Then we have the two mammillary bodies to be seen, and that's the posterior perforated substance. When you see the brainstem from the front, these four structures are present like this, right? That they're forming the interpeduncular fossa. But when you take a section, the same four structures are forming the floor of the third ventricle. You can see that. Let me just take you back to that point here. We've already done till, look at that. Can you see optic chiasm first? Then we have infundibulum. Then we have mammillary body, and then we have posterior perforated substance. Some part of the midbrain also, segment of the midbrain. This midbrain tegmentum is also there. But mainly these are structures which are, sorry, these are structures which are forming the floor of the third ventricle. Right? And in the recent time, there was a question asked on the mammillary body. Mammillary body was given, and the question was, mammillary body projects into which nuclei? It projects into the anterior thalamic nuclei. The fibers of the mammillary body that project into the anterior thalamic nuclei. That was asked here. So, in the question, in the picture like this, it's very important to identify the structure, identify where is the fornix, where is the choroid plexus, where is the pineal gland. If you can't identify the structures, the question doesn't make any sense to you. So, in the three sections of the brain, sagittal, transverse, coronal, identification of the structure is very important. Sagittal section, it gives you about the third ventricle, the boundaries of the third ventricle to be seen.

But Papez circuit, physiology topic. Papez circuit is like hippocampus. Hippocampus, say we have the starting of this, you know, the fornix. If I may show it to you, I'll come to that. In fact, I'll tell you a little about the Papez circuit, but though it is more of a physiology topic here, though this picture I have to give it to you because if the arrow was placed like this here, one of the arrow is placed just behind the midbrain, the lower part, that's midbrain here, that is the pons. So, behind the midbrain, guys, we know the only nerve which is emerging from the dorsal aspect of the brainstem. That is the fourth nerve. But make sure that you're looking at the arrow placed somewhere behind the midbrain. So, that is the fourth nerve. The second arrow is placed in the floor of the fourth ventricle. And we just discussed that it's the seventh nerve making a facial colliculus and coming out like this. So, it's the facial nerve. Facial nerve nucleus is sixth over there. The facial nerve is basically emerging like this, making a facial colliculus. So, if the arrow is placed somewhere behind the midbrain, like the upper arrow, then fourth nerve is the answer. If the arrow is placed somewhere in the floor of the fourth ventricle, then seventh nerve fibers can be seen in that region here. So, that's the two questions that could be asked from this in the dorsal aspect of the brainstem.

This section over there is a coronal section. This section here is, is a, is a coronal. Uvula, prana, anatomy makes me cry. Yeah. Okay. I know that you'll be asking, you are asking that when the class is going to get over. Coronal section, guys. In the coronal section, see what you're going to see. That this time, this here is the, sorry, that's the lateral ventricle, and that's the third ventricle. Third ventricle, already I want to look at this way. If you've already done with the third ventricle, now we know the lateral border with the third ventricle is by the thalamus. This is thalamus. Roof of the third ventricle, when we saw that, roof of the third ventricle is by choroid plexus and fornix. Now, this is the choroid plexus, and this over there is the fornix. We already saw that in the sagittal section, the roof of the third ventricle is by fornix and choroid plexus. The only difference is this time, the, this time the view is different. So, when you look at the coronal section, the roof of the lateral ventricle is by corpus callosum. That is internal capsule. Internal capsule. If I go more outside, guys, then the internal capsule. Once the internal capsule reaches above, you can see the fibers are radiating in all directions, that is called the corona radiata. This internal capsule, that is corona radiata, is there. We go further more outside, then we have this lentiform nucleus, and outside the lentiform nucleus, we have this hidden lobe called the insula. Insular cortex is there. Insula was one of the first image-based questions asked in anatomy, guys, 2014 question. 2014, they gave this coronal section, and their question was that where is insula in this picture? The insula is, it's a hidden lobe, unless when you open the lateral sulcus, then only you're able to appreciate this insula in that way. That's the lentiform nucleus, I already told you.

Now, from the third ventricle point of view, from the lateral ventricle point of view, the roof of the lateral ventricle is corpus callosum. Medial wall is by a thin septum called the septum pellucidum. That is septum pellucidum. And then everything is the floor, guys. The lateral ventricle, there is a roof, there is a medial wall, and then we have a sloping floor. You put a floor here, this whole thing is a floor. Only this, this whole thing is a floor of the lateral ventricle, where we have what? Where we have caudate nucleus, where we have thalamus, and we have the fornix and the choroid plexus. The fornix and choroid plexus, just look at it up close. So, you're looking at the septum pellucidum forming the medial wall, and the floor is formed by this, the caudate nucleus. There is a fornix, there is a choroid plexus which is present in the roof of the third ventricle, and thalamus is there. The basic identification of these structures is very important because the question, again, the question could be asked on anything, but you've got to identify the septum, where is the caudate nucleus, how exactly the fornix is going to look like in the coronal section. So, just a basic identification is definitely to be done.

This is a picture where I can tell you a little about this, you know, the Papez circuit also, but I don't want to go into too much detail of that, guys. What you see over there, that the blue colored fiber over there is the fornix. The fornix is something which you cannot see in one section very clearly. It's very obliquely placed fibers here. Fornix is a white matter bundle which is basically originates in the hippocampus. That was a question asked in the exam. It's one of the INA question only. Fornix is a white matter bundle. The fibers of the fornix start where? In the hippocampus. They originate in the hippocampus and they come downward and forward, and that terminates in the mammillary body. The termination of the fornix in the mammillary body. Fornix is a type of a projection fiber, association fiber. Fornix up. Fornix is an association fiber also. It is a commissural fiber also. It's a projection fiber also. And the, the purpose of the fornix is to originate from the hippocampus and terminate into the mammillary body. Mammillary body then projects into the anterior thalamic nuclei. Anterior thalamic nuclei projects into the cingulate gyrus, and cingulate gyrus via the cingulum again projects into the hippocampus. And that is the whole Papez circuit. Papez circuit can, what I'm saying is that there is hippocampus, hippocampus via fornix, via fornix, hippocampus is projecting into what body? Mammillary body. Mammillary body projects into the thalamic nuclei, that is anterior thalamic nuclei. Anterior thalamic nuclei projects and it projects into the cingulate gyrus of the brain, which is present on me. Cingulate gyrus, via a white matter bundle called the cingulum, it projects back into the hippocampus. You put a circuit, Papez circuit, guys. That's the Papez circuit of emotional integration. That hippocampus projects via fornix fibers into mammillary body. Mammillary body goes into the thalamus, anterior thalamic nuclei. Anterior thalamic nuclei send the, you know, the, what do you say, radiations into the cingulate gyrus. Cingulate gyrus projects back into the hippocampus. That's the, the Papez circuit over there. Bad insula.

Okay. The third and final section in the sectional anatomy of the brain is a transverse section. Guys, when you take a transverse section of the brain, now again the same thing. Can you see that white matter bundle? This, this is somewhere we have the genu of the corpus callosum. If, just imagine if the corpus callosum is somewhere here, that's the genu of the corpus callosum. And here we have the splenium of the corpus callosum. The fibers of the genu of the corpus callosum are going forward, and that is called the forceps minor fiber. So, that they come forward and connect the frontal lobe. That is the forceps minor fiber. From the splenium of the corpus callosum, look at the fibers which are running backward. These are called the forceps major fiber. And forceps major fibers are such thick fibers. They produce an elevation in the posterior horn of the lateral ventricle called the bulb of the posterior horn. Look at that bulge over there. Can, can you see that elevation, guys? This elevation which is present in the, in the medial wall of the posterior horn, in the posterior horn of the lateral ventricle, elevation, that is called the bulb of the posterior horn. And this bulb of the posterior horn is because of the forceps major. It's the forceps major fibers which are responsible for producing this elevation. More lateral to this posterior horn of the lateral ventricle, we have another white matter bundle which is called the tapetum. Forceps minor, forceps major, and tapetum are nothing but the different fibers of the corpus callosum only. Your corpus callosum's fibers which are running in the different directions to connect the frontal lobe and occipital lobe, like forceps major connects the frontal lobe, and tapetum and forceps major, they mainly connecting the occipital lobe and lower part of the temporal lobe also.

What else is seen in this section? In this section, I can again see the internal capsule in between. That is internal capsule. Look at this L-shaped white matter, that is internal capsule. And this internal capsule is surrounded by, on the medial side, by the caudate nucleus and thalamus, and on the lateral side by the lentiform nucleus. And we have insula, more laterally placed here. That is the same relation, guys. The one relation that you see in the coronal section, you can see in the transverse section also. If I, if I just try to compare. Thank you, guys. Thank you. Thank you so much. If, if you try to compare this picture with the MRI image, though, look at this MRI image here, and if I try to compare this MRI image with this image, what I'm doing is, let me superimpose that MRI image on this, and you will see a magic. Look at that. Well, that's, that's very satisfying, right? If you look at this picture now, in this image, I can see both cadaveric image and MRI image. How to identify the structure? The same labelings are there. Look at the forceps minor, how the forceps minor looks like in the MRI image, and in the cadaveric image. How the caudate nucleus looks like in the cadaveric image, in the MRI image. In the cadaveric image, that is the lentiform nucleus. Lentiform. That is the thalamus here. This is the thalamus here. That's internal capsule. Look at that. This is internal capsule, which is shown over there. That is the forceps major. That is the forceps major. So, you can, kind of, most of the structures, you can compare on both sides. So, even if they give you a radiological image, or even if they give you a cadaveric image, I hope that you'll be able to easily be able to compare them, and you can still be able to identify the structures. Thank you, guys. Your messages are one which are, which are making me stay awake at 2 AM. It's, we, exactly, it's so, it's almost 2 AM now, but I'm not sleepy at all. Okay.

Cerebellar cortex, guys. Cerebellar cortex, very easy topic, but you get a lot of questions from there. When you look at the cerebellar cortex, the cortex part, guys, cortex. You can divide the cerebellum into cortex and the white matter. The cerebellar cortex having three layers. As you can see, there is a molecular layer. Look at that circle over there, which is having two types of cells: basket cells, stellate cells. We have a Purkinje layer. We have what? Purkinje cells. And we have a granular layer, which is having the two types of granular cells and Golgi cells. So, total there are three types, three layers in the cerebellar cortex. We have molecular layer, we have a Purkinje layer, and we have a granular layer. Molecular, Purkinje, granular layer. And total five types of cells are present there: basket, stellate, Purkinje, granule, basket cells, stellate cells, Purkinje cells, and Golgi cells. They are inhibitory cells. Inhibitory cells. Cerebellar cortex, it is like, it is, it is, you're so negative. It's like the cerebral cortex, but you're so negative. All negative cells are there. Inhibitory, inhibitory, inhibitory, inhibitory cells are there. The only excitatory cell which we have in the cerebellar cortex is a granule cell. So, it's a granule cell which is excitatory in nature. Sub-inhibitory. Okay. And that is why cerebellar cortex is the largest collection of inhibitory neurons in the entire central nervous system. In the whole central nervous system, inhibited neuron. There's the biggest collection of inhibitory neurons in the CNS. But the outermost layer is the molecular. Molecular is outermost. Then we have Purkinje. Then we have granular, guys. Collectively, thank you for all the messages that you're sending here. I would love to hear more of more of these, but, but after the class. So, I would love to read these messages, but, you know, let me just stay focused on on on on the slides, and then I would love to read everything that you were writing. Okay.

Now, out of all the cells, looking at a Purkinje cell, only Purkinje. This is a Purkinje cell. That's the only cell which actually comes out of the cortex. All other cells are having internal connections. The only cell which actually leaves the cortex and comes out in the white matter is the Purkinje cell to efferent from the cortex. Okay. What about afferent fibers? That is the fibers which are entering the cerebellum. There are two types of afferent fibers. We have climbing fibers and mossy fibers. Look, I say climbing fiber and mossy fiber. Now, look at the arrow first. Climbing fiber. The orange colored fiber which are shown as climbing fiber. The reason we call them climbing fiber because they can climb to the topmost layer and they're directly synapsing with what? Purkinje cells. That's why we call them climbing fiber. Second type, we have got mossy fibers. Mossy fibers are those which will come inside. But mossy fibers are going to connect to the Purkinje cells via these cells. And what these cells are? These are granule cells. Bag granule cells are the only excitatory cell, remember. And the reason they are excitatory cell because it's the responsibility of the granule cell. The mossy fiber connects with the Purkinje fibers here. So, we have two types of afferents coming into the cerebellum. The climbing fibers are the ones which climb directly to the to the molecular layer and and and and the Purkinje, what do you say? Uh, the mossy fibers are the ones which are going to use the granule cell. Granule cells, and then granule cells will connect them to the to the molecular layer. The question is, which fibers are climbing, which are mossy? Or easily and parvo-cerebellar. The tract, olivary, olivary word in the name of the tract, that is climbing fiber. The olivary, olivo-cerebellar, parvo-olivary, these are climbing fiber. Rest everything is mossy. Anything else coming into the cerebellum, sub-mossy fiber, whatever it is, guys, dorsal spinocerebellar, reticulocerebellar, pontocerebellar, this and that, whatever comes inside the cerebellum, everything is a mossy fiber, except olivary word. Olivary word is written in the tract. Olivo-cerebellar, paraolivo-cerebellar, superior olivocerebellar, all these olivocerebellar pathways are climbing. Rest everything else is mossy fiber. So, majority of the fibers are mossy fibers. Right? So, this is about the cerebellar cortex.

Now, if I just show you the histological picture of that, that is a picture that they love to give, and especially more in the more wide. That is the area. If I focus over there, that's the Purkinje cell. And I told you, what about the Purkinje cell, guys? Purkinje cell. Purkinje cell is the only cell which basically sends the efferent from the cortex. But when the Purkinje cell's efferent come out of the cortex, they come into the white matter. And in the white matter, we have what? Deep cerebellar nuclei. The efferent from the cerebellum will come from the deep cerebellar nuclei. Purkinje only efferent from cortex. But efferent from cerebellum will come from deep cerebellar nuclei. This, this arrow should not be there in between. Let me just, let's rectify this. This arrow should not be there. This is one information. Purkinje cells are forming the efferent from the cortex, and the efferent from the cerebellum will be coming from where? Deep cerebellar nuclei. Especially the dentate nucleus. Dentate nucleus is the main nucleus which is present in the white matter that sends the fiber outside.

One of the most commonly asked questions in the cerebellum is about the cerebellar peduncles. Now, there are three cerebellar peduncles, guys. If you just try to get an orientation to the picture, you're looking at the cerebrum there. That's cerebrum here. This triangle is the thalamus. Let's say this is the thalamus there, and looking at three parts of the brainstem: midbrain, pons, and medulla oblongata. You can see the midbrain is connected to the cerebellum by this yellow colored peduncle. Superior peduncle. This is the middle peduncle. There is an inferior peduncle. These are cerebellar peduncles. First of all, do not confuse the cerebellar and cerebral peduncles. The cerebellar peduncle. One easy way. Middle cerebellar peduncle. This tract here is the corticospinal tract. The one copy, guys, when the corticospinal tract comes down, one copy of corticospinal tract goes into the cerebellum, and that copy of corticospinal tract is called the pontocerebellar tract, and that is entering the cerebellum through which peduncle? To the middle cerebellar peduncle. That is called the pontocerebellar tract, and pontocerebellar tract is the only major tract that you see passing through the middle peduncle. Middle cerebellar peduncle is purely afferent, that means middle cerebellar peduncle is allowing the tract only to come inside. It's purely afferent. Biggest peduncle or purely afferent.

Superior cerebellar peduncle is giving passage to one tract called the ventral spinocerebellar. The ventral spinocerebellar tract from the superior peduncle, and the efferents which are going from the dentate nucleus, the feedback which is going from the dentate nucleus, the feedback from the cerebellum going from what nucleus? Dentate. That's the dentate nucleus over there, guys. That's the dentate nucleus. So, these tracts are called dentothalamic and dentatorubral, going through the red nucleus. Dentatorubral, dentothalamic, and dentatorubral. So, these tracts are passing through what peduncle? Superior cerebellar peduncle. These tracts are passing through what peduncle? Superior cerebellar peduncle. The two major tracts passing through the superior cerebellar peduncle are these. The only tract from the middle cerebellar peduncle is what? Pontocerebellar. And rest everything from the inferior cerebellar peduncle. So, why to read inferior cerebellar peduncle? I mean, everything else is from the inferior cerebellar peduncle only. So, don't read them. If it is not dentothalamic, if it is not ventral spinocerebellar, if it is not pontocerebellar, it is passing through which peduncle only? Inferior cerebellar peduncle. Everything else is from the inferior cerebellar peduncle. So, my suggestion here to you here is, peduncles, guys. Don't read inferior peduncle because we have maximum number of tracts present in the inferior peduncle. So, keep it simple. Ventral spinocerebellar, dentothalamic, dentatorubral, that is like efferent, the feedback coming from the cerebellum. These pontocerebellar from the middle peduncle, and everything else is from the inferior peduncle. There is a long list of tracts passing from the inferior peduncle: dorsal spinocerebellar, cuneocerebellar, reticulocerebellar, olivocerebellar, paraolivary cerebellar, cerebellorubral, cerebellovestibular. If you know the superior peduncle, if you know the middle peduncle, everything else is from which peduncle only? Inferior peduncle. You can easily eliminate the option and reach the right answer. Be smart in this. Yeah.

Okay. Now, again, moving on to a few more slides that, as you can see, I'm just introducing some three, four, three, four, three, four slides in between, in between, so that we keep on covering histology as much as we can. Now, guys, you're looking at a picture. Now, this time we're discussing the cartilages. Now, this is a picture of hyaline cartilage. Now, how can you say it's a hyaline cartilage picture? First of all, in the hyaline cartilage, you can see there is a, there is a perichondrium present. Collagen and type two collagen fibers. There we have perichondrium present, and perichondrium has two layers, guys. We have an outer layer of perichondrium, which is basically called as a fibrous. This is the fibrous layer of perichondrium. And can you see these flattened cells over there? That's the inner layer, chondrogenic layer. Outer fibrous layer and inner layer is the chondrogenic layer. Chondroblasts are there, but that is not the identifying feature. The identifying feature of the hyaline cartilage is, look at that. Can you see the chondrocytes which are present in lacunae are present in clusters? Clusters of four, five, four, five, three, two, all these clusters are present, and these clusters are called cell nests. They're making cell nests. So, three, four chondrocytes will come together and they form their own nest over there, called a cell rest. Nest. It's like multiple nests are present inside, and we have a darkly stained present matrix present around them, which is called the territorial matrix, and you can see the light blue, light colored matrix present in between them, called the interterritorial matrix. So, we have a territorial matrix around them, dark one, and the interterritorial matrix is light one. It's a good enough hint to identify it's a slide of hyaline cartilage. Chondrocytes are seen present collectively, making cell nests, having a darkly stained present matrix around them, called territorial, and the lightly stained matrix is interterritorial matrix. And remember, the perichondrium is present. It's a slide of hyaline cartilage.

What slide is this one now? This is a slide of elastic cartilage. How come it's elastic cartilage? Elastic cartilage, again, perichondrium is there. Again, same thing, guys. We have chondrogenic layer, the same thing, outer fibrous layer, cellular layer. Now, we have chondrocytes present, present inside, but these chondrocytes are individually placed. Look at these chondrocytes present over there. The chondrocytes are individually placed here. It's not, there's no cluster. You cannot make out territorial, interterritorial matrix. It's like separate, separate chondrocytes are present. In this elastic fibers, we are not able to see because H&E slides, you will not see, guys. Eosin and hematoxylin cannot stain the elastic fibers. So, I'm not able to see any elastic fiber in this. Right? So, even by the method of elimination also, you can reach them. Remember, chondrocytes, fibrocartilage may be elastic cartilage, hyaline cartilage. Chondrocytes are present. In elastic fiber and hyaline cartilage, if the chondrocytes are present in clusters, territorial, interterritorial matrix, and there is a perichondrium, it's hyaline cartilage. If chondrocytes are present individually like this here, there is a perichondrium, but chondrocytes are present over there, but no cell nests, no territorial, interterritorial matrix, that is elastic cartilage. But if it's a fibrocartilage, first of all, there is no perichondrium. If it's a slide of fibrocartilage, there is no perichondrium. Number two, no perichondrium. Number two, the collagen bundles are present in such a way that all these collagen bundles have squeezed these chondrocytes in a line. Look at the collagen bundles present over there. And because of numerous collagen fibers, chondrocytes are now arranged in a line, in linear fashion. And these chondrocytes arranged in a line in rows is the feature of the fibrocartilage. It's the feature of the fibrocartilage. So, simple: chondrocytes individually, chondrocytes, big chondrocytes can be seen individually, elastic cartilage. Chondrocytes seen in clusters of three, four, three, four, three, four, hyaline cartilage. Chondrocytes present in the line, in the series, fibrocartilage. Simple, you can easily identify the cartilage slide just by remembering these few features only.

Okay, moving on to our last spurt. So, let's, let's finish this off, guys, strongly. So, in the abdomen and perineum, again, a topic which needs to be done very selectively. This is not, I'm not just saying because of the one-shot thing, because abdomen and perineum is something OBG, surgery. The more of an OBG and surgery-based question will be asked from this abdomen and perineum. So, when it comes to core anatomy, some few topics from the per, perineum, and I would say some topics from perineum that is important, especially perineum, which I'm going to discuss with you, is more important here. Yeah. Now, look at this. This picture here is a transverse section of the abdomen where you can see the epiploic foramen. Let me give you a little orientation first. What you're looking at right now in the transverse section, guys, this here is the stomach. That's the stomach over there. That's the spleen. This is the lesser sac. Blue colored sac over there is the lesser sac, and this is the lesser omentum. That is the liver over there, and this is the lesser omentum. That is the left kidney, right kidney. You can see the aorta there, and you can see the inferior vena cava also. This, where I'm pointing right, look at my laser pointer there, this exactly is the point where we have the epiploic foramen, also called the foramen of Winslow. That is also called the foramen of Winslow. Epiploic foramen is an important area because epiploic foramen is a site, guys, which is the only connection between the greater sac and the lesser sac. Though this sac here is the lesser sac, and everything in front is the greater sac. Epiploic foramen is the only connection. And any herniation through the epiploic foramen is usually a big headache for the surgeon because you cannot increase the size of the epiploic foramen. Why? Why can't we increase the size of the epiploic foramen? Because of the relations. Look at just the entry to the epiploic foramen. What we have? What relations are there? We have the portal triad: portal vein, hepatic artery, bile duct. So, anterior relation of the epiploic foramen are the portal triad. And similarly, posterior relation of the epiploic foramen are also very important because posteriorly we have the inferior vena cava, we've got the right suprarenal gland, yeah, right suprarenal gland, and T12 body. That is the T12 body there. That we have IVC, and that's the right suprarenal gland is also there. Veins are more important. I mean, you need to know the other relations also. But when it comes to the epiploic foramen or foramen of Winslow, just remember that just in front of the epiploic foramen, we have this vein, that is, that is the portal vein. And just behind that, we have the inferior vena cava. And that makes this area kind of, I mean, the area where you cannot increase the size. What will you compromise? Can you compromise the portal vein? Can you compromise the inferior vena cava? That's why increasing the size of the epiploic foramen is not possible. And that's why it's a difficult hernia to deal with if the intestine herniates to this epiploic foramen inside. And in fact, that's the only connection between the greater sac and the lesser sac. Right? So, this is something that you have to remember in the transverse section. That's an important, important opening that you need to know about.

If you look at a longitudinal section, guys, once again, if you go with the same color code, only this blue colored space over there, that is the lesser sac. Lesser. That is the lesser sac that you see. And look at that arrow that is passing through the epiploic foramen. That tells you that the greater, the green one, that greater sac is connected to the lesser sac through this epiploic foramen. The question here is, what are the relations of this lesser sac or the omental bursa? Lesser sac is also called the omental bursa. And in the, in the recent time also, they've asked this relation of the omental bursa. If you look at the anterior relation of the omental bursa or lesser sac, the anterior relation of the lesser sac is the liver. Look, let me just point out the laser on that. That is, that is the, that is the caudate lobe of the liver. This one here is the lesser omentum. That's the stomach, and we have the anterior two layers of the greater omentum also. So, lesser sac, anterior relation, we have the caudate lobe of the liver, number one. You can see in the picture. We have the lesser omentum there, is the stomach, and there are anterior layers of the greater omentum. Posterior relation of the lesser sac involves the stomach bed structures. Stomach bed, I hope that you all know that what is there in the stomach bed, guys? What is behind the stomach? Left kidney, left suprarenal gland, there is, there is, there is, there is left crus of diaphragm, there is transverse mesocolon, there is, you know, what do you say? We have the pancreas there, spleenic artery, whatever structures are there in the stomach bed are also present behind the lesser sac, stomach, except spleen. That's a question. So, spleen is a structure which is in relation to the stomach, but spleen is not present behind the lesser sac. That's, that's their main, main thing to ask in this, guys, that which of the following structure is not forming the relation of the lesser sac? Spleen. Spleen is the answer to that. So, in the lesser sac, anterior relations are visible there. Posterior relations are the structures of the stomach bed, except for the spleen. Spleen is not in the posterior relation. Thank you, guys. Thank you. Thank you so much.

Okay. Now, this is somewhere which, which, which this is where I want all of you to focus because there's almost a guaranteed question from this part here, that is perineum, guys. Pelvic diaphragm, superficial pouch, deep pouch, perineal body. So, I want you just to focus for next 15. I, I think I should be able to finish it next 15, 20 minutes only. So, I want you to focus especially on the next 15 minutes, which is about the perineum, very, very carefully. All of you, just look at the screen, and I'm sure that you're going to enjoy this part here. Yeah. See what you're looking at right now. You're looking at the pelvic bone in the lithotomy position. Pelvis, when you look at the pelvic bone from the lithotomy position, guys, what you look at, that is the, that is the pubic symphysis there, right? This here is the pubic symphysis. This is the ischio-pubic ramus tuberosity. That ligament is connecting the sacrum, and this is tuberosity called the sacrotuberous ligament. There is a sacrotuberous ligament. In the pelvic diaphragm, first of all, what is pelvic diaphragm, guys? Pelvic diaphragm is something which is separating the pelvis and perineum. And pelvic diaphragm is a combination of three muscles. One, the three muscles coming from three different parts of the hip bone, and all these muscles are coming toward the coccyx, coccygeal vertebrae. So, we have muscles coming from the pubis, which is called the pubococcygeus. That's the pubococcygeus. We have muscles called the iliococcygeus, and we have muscles called the ischiococcygeus. All muscles are coming to the coccygeal vertebrae, so we call them coccygeus. We have pubococcygeus, we have iliococcygeus, and we have ischiococcygeus. All these three muscles together are called what? Pelvic diaphragm. When you consider all these three muscles together, that is called the pelvic diaphragm. But what's the difference between the pelvic diaphragm and levator ani? I'm sure you've heard of the word levator ani, and pelvic diaphragm are used interchangeably. Levator ani is a combination of pubococcygeus and iliococcygeus, guys. Ischiococcygeus is not part of the levator ani. Levator ani are the muscles which are capable of elevating the anal canal, and only pubo and ilio muscles are considered the part of the levator ani, not ischiococcygeus. The difference between the pelvic diaphragm and levator muscles: pubo, ilio, that is levator ani. When you say all the three muscles together, that is pelvic diaphragm. Simple. Let's say this is a picture of female perineum. Now, if this is a picture of female perineum, the three openings that you see: one is the opening for urethra, vagina, and rectum. Urethra, vagina, rectum opening. Now, guys, what is the muscle closest to all the three openings? That is pubococcygeus. Pubococcygeus muscle is closest to all the three openings. So, you will see extensions coming from pubococcygeus, like there is a muscle called pubourethralis, pubovaginalis, and puborectalis. Pubovaginalis, pubourethralis, that is covering the urethra. Pubovaginalis, that is covering the vagina. And puborectalis, covering the rectum. These three are the modifications of what muscle only? Pubococcygeus. So, pubococcygeus muscle is present, and that is sending extensions covering the urethra, vagina, and rectum, and these are the modifications of the pubococcygeus muscle: pubourethralis, pubovaginalis, and puborectalis muscle. Okay. Now, that's pelvic diaphragm for you, guys. And puborectalis muscle is an important muscle because it maintains the angle, it maintains the anorectal angle, muscle of continence. Okay. That's the first look.

Understand one thing. When you're looking at the perineum, let's say this is the pelvis for me. So, you're looking at it like this, when you're looking at the pelvis from below. So, first you saw the pelvic diaphragm. Now, below the pelvic diaphragm, there's another diaphragm present there, and that diaphragm is present only in this area where urinary and genital structures are present. So, this is called the urogenital diaphragm. This green diaphragm that you're looking at right now, that is called the urogenital, because that is present in the urogenital triangle. So, it is called the urogenital diaphragm. But understand, the urogenital diaphragm is having two layers. One is a superior layer, and one is an inferior layer. Inferior layer. You're looking at the inferior layer of the urogenital diaphragm. This green one is inferior. Superior layer is there. This is the inferior layer of the urogenital diaphragm, which is also called the perineal membrane. This is called the inferior layer of the urogenital diaphragm, which is also called the perineal membrane. Guys, it is also called the perineal membrane. To story be first, it was a pelvic diaphragm. Then we have the superior layer of the urogenital diaphragm, which we haven't seen. Superior layer of urogenital diaphragm, and then we have the inferior layer of urogenital diaphragm.

And below the inferior layer of urogenital diaphragm, now you will see the muscles which are covering the bulb and the crus of the penis. Let's say it's a male perineum here. So we have the muscle covering the bulb of the penis called as bulbospongiosus. And we have the muscle which is going to cover the crus of the penis called as ischiocavernosus. Muscle covering the bulb is bulbospongiosus. Muscle covering the crus is called as ischiocavernosus. And we also have a muscle which are running horizontally transversely and this muscle is called as a superficial transverse perineal muscle. This muscle is present below the perineal membrane. So we call it a superficial transverse perineal muscle.

So guys, before we go further, uh, thank you guys. Thank you. Thank you so much. So when you look at this pelvic diaphragm is there. Then we have superior layer of urogenital diaphragm. We haven't seen that. The green one over there is the inferior layer of urogenital diaphragm. And below the inferior layer of urogenital diaphragm, you're looking at the bulbospongiosus, ischiocavernosus, transverse perineal muscle is there. So these are the layers of perineum we're looking at here.

If I take you to the posterior triangle, there we have an anal canal there and the anal canal is surrounded by this external anal sphincter, guys. That is external anal sphincter covering the anal canal and this junction, look at this this coalescing body over there, that junction is called as a perineal body. So it's a fibro muscular node, guys, that that is a region where most of these muscles are converging into this perineal body and that's why in especially in the episiotomy, we are very careful not to injure the perineal body. Perineal body injured, obviously, the rectal prolapse or the prolapse can take place because it is a common point of insertion of all these muscles. What makes the perineal body an important topic, guys? Perineal body, they ask you that. That's a picture to compare. If if I just look at this picture and compare it, what are you looking at, right? That membrane over there is a perineal membrane, agreed? Perineal membrane. What is this muscle? That is bulbospongiosus. What is this muscle? That is ischiocavernosus. What is this muscle? That is a superficial transverse perineal muscle. And this over there is a external anal sphincter. That is perineal body.

Now the question here is that what are the muscles which are contributing to perineal body or mistake usually perineal body. What is there in perineal body? There are total 10 muscles in perineal body. Out of the 10 muscles, guys, we have four muscles which are paired. What are the paired muscles? We have superficial transverse perineal muscle. If you have superficial transverse perineal muscle, there will be deep also. But there is a deep transverse perineal muscle is also there. Then we have what muscle? Bulbospongiosus. And this is where we commit the mistake. Fourth muscle is not this one. Let me tell you, this is not the issue. Muscle is not the part of issue. Muscle is on the side. How can it be in the coronal body? So it's actually levator ani. So fourth muscle, remember it's not ischiocavernosus, it's levator ani which is contributing to the perineal body. What are the unpaired muscles? Unpaired muscle may be have external anal sphincter. And because anal canal is not only having the sphincter, it is having some longitudinal muscles also. So some longitudinal muscles of anal canal are also contributing to it. It's a question asked in the exam, guys. Perineal body, what are the muscles which are contributing to perineal body? So total 10 muscles, four paired, which makes them eight. What are the paired muscles? Superficial transverse, deep transverse perineal muscle, bulbospongiosus, and not is not ischiocavernosus, it's levator ani which is contributing there. Okay.

Now if I take a little section of perineum, how it is going to look like? If I take a sagittal section of perineum, guys, the same thing like if if I if I turn sideways, if I take a sagittal section, the first layer is pelvic diaphragm, then we have superior layer of urogenital diaphragm, then we have inferior layer of urogenital diaphragm, bulb of penis, and then we have a cloaca which we have to talk about. Now look, let's say this is a sagittal section. What is this? That is pelvic diaphragm. We are going from above downward. Neck first is pelvic diaphragm. Just below pelvic diaphragm, we have got superior layer of urogenital diaphragm. Just below that, we have inferior layer of urogenital diaphragm, also called as what? Perineal membrane. That is pelvic diaphragm. This green one is a superior layer of urogenital diaphragm. This red one here is a inferior layer of urogenital diaphragm or perineal membrane. This is a mid-sagittal section. So going from the bulb and the shaft, that is a bulb and the shaft of the penis and obviously bulb or shaft penis, you also able to see urethra. Look at that urethra which is passing through that. That's a urethra there. The question is what is below? What is below that? For that I need to start from the anterior abdominal wall. Anterior abdominal wall. I'm sure you all know that on the anterior abdominal wall, we have this fascia called as a Scarpa's fascia. Right? That is a Scarpa's fascia is there. Swastik, think that's a good one. Scarpa's fascia. Scarpa's fascia, which is anterior abdominal. The the Scarpa's fascia will continue in the scrotum in the form of the muscle called as a dartos muscle. We see contamination dartos muscle and dartos muscle will continue as fascia called as a Colles' fascia. Guys, look at that. Look at the blue color over there. There is a Scarpa's fascia here. This Scarpa's fascia will continue as what? Dartos muscle and then the dartos muscle will continue as this fascia which is now called as a Colles' fascia. So Scarpa's, dartos, and Colles' fascia, they are all in continuity. Only. They are all in continuity. Once you draw this Colles' fascia and you can see this Colles' fascia merging with this perineal membrane here, perineal descending layer of perineal membrane, guys, look at this one space over there. The space which is present above is called as a deep perineal pouch and the space which is present below is called as a superficial perineal pouch. The deep perineal pouch and the superficial perineal pouch. It is right to say that deep perineal pouch is nothing just the space between the superior layer, I'm sorry, between the superior layer and the inferior layer of urogenital diaphragm. That space is called as a deep. Deep perineal pouch is a space inside urogenital diaphragm. Urogenital diaphragm space, deep space inside the urogenital diaphragm is deep pouch and the space below the urogenital diaphragm is superficial pouch. Now knowing if this is a deep pouch and that is a superficial pouch, now there is one very important question which is asked in the surgery also and I want to look at that, guys. Now again, I'm putting the same picture for you guys. What urethra is this? The urethra that you see over there, this urethra here is the membranous urethra and this urethra here is a bulbar urethra. Now you tell me if there is a rupture of the membranous urethra, urine accumulate. If there is a rupture of the membranous urethra, the urine will accumulate in what pouch? Only in the deep perineal pouch. Look at this arrow over there. The urine is going to accumulate in the membranous rupture. The urine accumulates in what pouch? Deep perineal pouch. Simple. But if there is a rupture of the bulbar, if the bulbar is injured, the urine will first go into what? Superficial perineal pouch. Now unfortunately, superficial perineal pouch is not having anterior wall. There is no anterior wall of superficial perineal pouch. So urine can easily come into the scrotum. It can even go to the anterior abdominal wall also. So if there is a rupture of the to the spongy urethra, the urine can go into the scrotum and Scarpa's, especially fascia, can even go behind the anterior abdominal wall and maybe to the upper part of thigh also. So that is a that is a case that if there is a rupture of bulbar urethra, then because there is no anterior wall of superficial pouch, so urine can go into the superficial pouch, into the scrotum, into the abdominal wall, and into the thigh, upper part of the thigh also. So if they ask you a question on membranous or bulbar, please remember what to be answered in there. Yeah. Yeah. Urine and excrete. Exactly, Krishna. That that that that is also possible. You may have the urine reaching till the axillary wall also. Weird but true.

Okay. Guys, coming to this last gross topic here. Ischiorectal fossa or ischioanal fossa. I'm just going to wrap it up in the next 5-10 minutes only. Ischiorectal or ischioanal fossa. What is ischioanal fossa? If you look at this anal canal, that is the anal canal over there. This here is the skin of the gluteal region. I'm just comparing the picture. Square the gluteal region and on the lateral side, there is a muscle which is called as a obturator internus. There's a muscle here. There's obturator. Lateral wall is obturator internus muscle. If it is an anal canal, guys, obviously that is obturator internus and that's this is external anal sphincter. That that over there is external anal sphincter and this is the levator ani. That is levator. You can compare this with this picture above, guys. You can see this here is the obturator internus muscle. This is a external anal sphincter. There you can see and this obliquely placed muscle is levator ani or you can say pelvic diaphragm. Levator ani or pelvic diaphragm is there. Now look, levator. Can you see the fascia covering the obturator internus? It is called as a obturator fascia. And this obturator fascia, it gives rise to a canal on the side which is called as a pudendal canal. This obturator fascia only will give rise to a canal and this canal is called as a pudendal canal. Let me just try to show you the pudendal canal in this picture also. Guys, I thought a clearer picture, but I hope you can still manage to see. Can you see a little canal over there on the side here? Look at that here. That canal which is made up of obturator fascia. It is called as a pudendal canal. It's the same pudendal canal which is giving passage to the neurovascular structures, guys. Pudendal nerve, internal pudendal vessels, they will be passing through this pudendal canal. You can see pudendal nerve is going through it and internal pudendal vessels are also going through this pudendal canal only.

Now, so first of all, bound. If this fossa here is, guys, this is the ischiorectal fossa. So I can say in the ischiorectal fossa, the medial boundary, lateral boundary of ischiorectal fossa is by external anal sphincter and levator ani. And that is the medial boundary. Lateral boundary is by obturator internus and that obturator internus fascia is forming this pudendal canal also, holding the pudendal nerve. Now if I see this in the transverse section, if I look at the same thing in the transverse section, how it is going to look like? Now look, if you look at the same, we already have discussed this area, so I don't have to talk about this region, guys. We already discussed this. Now I want to take your attention here. In this picture, you can already see anal canal there. You can see the external anal sphincter. Now pudendal canal is present something like this, roughly. Pudendal canal is present on the side and this pudendal canal is giving passage to what nerve? Pudendal nerve and internal pudendal vessels. That's a pudendal nerve and internal pudendal vessels are passing through it. If you have a patient who's having an ischiorectal fossa abscess, now you can easily put an incision like this. You can drain the ischiorectal fossa, no problem. But there is one nerve and there is one artery which is actually running transversely in the ischiorectal fossa called as inferior rectal nerve and inferior rectal artery. And this inferior rectal nerve and artery are vulnerable to injury in the drainage of ischiorectal fossa. The ischiorectal fossa main content of fat. There is fat as a content. Pudendal canal is a content. But the problem is these contents, because rest of the contents are very safe on the side. These are the only structures running horizontally in the ischiorectal fossa called as inferior rectal nerve and inferior rectal artery. So if you have a patient who is having ischiorectal fossa abscess, while draining the abscess, you may injure these structures. These structures are vulnerable to injury in the drainage of ischiorectal fossa abscess. That's the main question they ask you in the ischiorectal fossa that what are the structures which are uh which are you know which are vulnerable to injury in the drainage of ischiorectal fossa abscess and the answer is inferior rectal nerve and artery. Inferior rectal nerve and artery.

Okay. Finally, the one last slide for guys, that is a question which is also asked in the recent time that is about the tongue papillae. Now when you look at the when you look at the tongue papillae, see, just I want you to notice very few basic things here. You don't have to go into too much of detail and histological part of it. It's easy to identify the papillae. First of all, you have the filiform papillae which are like conical projections are there and the filiform papillae, they do not have the taste buds. Forget about it. So that is filiform papillae, there's no taste bud on them. Now we have fungiform, foliate, and vallate papillae. In the fungiform papillae, you can see there, there are these pits are there. We have these these pits are there on the papillae on the side here. Right? The taste buds are present on the dorsal surface, on the surface. On the top surface, we have the taste buds. So if you see the pits are present on the side and the taste buds are present on the top, on the dorsal side, it is a fungiform papillae. It is slightly mushroom shaped. But the problem is surface. If you have the straight pits, if the pits are straight, you can see these pits over there. They are more or less straight only. But the taste buds are present inside the pit, not on the dorsal surface. Can you see the the taste buds are present inside the pit, not on the dorsal surface? It's a foliate papillae. And if you see it is mushroom shaped, shaped like fungiform only, it is mushroom shaped. But the instead of on the dorsal surface, if the numerous numerous taste buds are present and these taste buds are present in the furrow, in the pits, then it is vallate or you can say circumvallate papillae. Based on that, the question given in the exam was this one. Can you see that it's a foliate papillae? Now, how come it's foliate type? Because first of all, you have a straight furrow. Straight pits are there. And guys, it may enlarge this. Taste buds. Taste buds. Taste buds. Taste buds. Taste buds. All these are taste buds present in the furrow. There is no taste bud present on the surface. Nothing on the surface. If it was present on the surface, it would have been the the fungiform. This is a foliate papillae. Let me show you the one which is more like a mushroom shaped. And you again have the taste buds present. That would be vallate or the circumvallate. And that is this one. Look at that. Can you see? First of all, the shape is little like mushroom shape. Broad above and narrow below. And if I take you again, nothing on the surface. Nothing on the surface above. But look at the pits over there. And look at the number of taste buds present inside. There's so many taste buds present inside. There is what papillae? That's a circumvallate. So keep it simple. Conical projection like filiform. Then we have the one which is slightly mushroom shaped but the taste buds are on what surface? That is what fungiform. If you have mushroom shaped but the taste buds are present in the pit, that is circumvallate papillae or vallate papillae. If you have more like a straight furrow and the taste buds are present in the pits, then it's a vallate papillae. So whatever kind of taste this the this taste buds are given to you, I'm sure you will be able to identify. They will give you circumvallate or foliate papillae only to identify. Two to kind of fight between the two, like yes. So that is about the swastik major. Yeah. Hello guys. So that is about the vallate papillae. So guys, that concludes the discussion of this. Whatever time was committed to you, the we we are able to finish it on on on that time itself. Okay. Yeah.

So guys, this is about this is about the anatomy one shot. The many of the people are asking that in the anatomy one shot, that how much is is it enough or it is it is I cannot say how much is enough, but I'm pretty sure that if you have done this much, you will not come disappointed for the anatomy or out of examination hall. You will be able to. If you are someone who attended my lecture earlier and you're now looking at the one shot, it is very, very beneficial. But if you are someone you have never read anatomy or read anatomy from other source, whatever experience you had over there, let's not talk about that. And if you kind of want to rely on this on this uh on this one shot, still it is not going to disappoint you. I can promise you that. And that you can see in the in the INCT which is very, very uh if it is going to happen in few days itself, you will see that how much of anatomy you will be able to attempt in this. If the INCT gives you a confidence from this one shot, then I think you you will you will gain more confidence. Okay. I can carry this the same thing forward into the the NEET exam also. And you know guys, talking about the exam, I I just just want to. I'm not going to preach or anything here, but I'll tell you one one thing about the examination that there are so many expert faculties who have whom you have met and they have given you such some great suggestions here. I just just want to tell you a little, you know, a little fact about it about this examination. All even, you know, even at this age, even at this point of time in my life, even even if I sit in front of the of the grand test or the questions which are asked in the exam for you people, I start having anxiety. PG exam, I don't have to do anything now, but still I get an anxiety here. So it is the pressure which is basically refraining you from where you want to reach. Example, guys, if I put a plank, if I put a two feet plank on the road and I want to walk, walk on this plank, will you be able to walk on it effortlessly? Two feet, two feet plank. We can jump, we can jump, we can dance, we can stand on one leg, we can do anything effortlessly. We can do that, right? The two feet plank. The same two feet plank. Let me put it on the edge of the building now. Let me take the same two feet plank and I put it on the edge of the building, top of the building here. And now I ask you to walk on it here. Now what happened? You're trembling. You're not able to do it. You're not able to walk. We same. It's the same plank only. Now it's the same two feet plank on which you were dancing just a minute earlier, and now you're not able to walk on it here. The reason it's not the plank. It's not your ability. It's the fear. It's the fear of falling. It's the fear of consequences. You're like, what will happen if I fall down? While I despite of it's a very easy job to be done because the fear is something which is creeping in that is not letting you do it. This is exactly what happens in the examination. All when you're sitting in front of the screen, when the questions are triggered in front of you, the question which is not not scaring you. It's the question and the consequence which is coming in your brain. If I got this question wrong, then one wrong is there, negative marking will be there, that'll affect my rank. This keeps on going on in your head and that basically, you know, affects your the entire thing. The people who are able to do good in these examinations, in this PG entrance or any entrance examination are the one who are able to handle themselves mentally better. So, you know, at on the given day, when you're in that examination hall, your knowledge obviously is counted, but I I very genuinely feel and it's very generally I'm saying, it's not just just to you know, just to show you some pictures and to motivate you only, it that it's about how confident you feel about it, how, you know, you feel that the result doesn't matter. Easier said than done, obviously. I as I said, even at this age, I can't do that so so effortlessly. Because if I give you the same questions in a test sitting in comfortably in your hostel or or bedroom, you might be able to do it. The same question on the computer screen when the NEET exam is going on, the pressure, the environment, the consequences, what result is going to do is basically going to pull you back here. That's why give grand tests as many as possible, especially with all these the uh the national grand tests that we have, so that you basically get, you know, sometime you get a good start, sometime you get a bad start, you just basically learn to walk on that two feet wide plank, be it on the top of the building or on the flat road, you should be running effortlessly on this. And with that, I thank you so much, guys. I I I hope that this one shot session, not only mine, my I'm the last one here. I was supposed to be on the fourth day that they helped you kind of helping you to revise your subject um efficiently. And one more thing on the 16th of uh of this month, we are also having uh the Marrow is also, you know, conducting this, if I may tell you, uh on the uh to support your, you know, the preparation, a free Marrow mock test will be live on the 16th of May. After this for this one shot thing here. So I would it's free, why not do it? So please go and give it and and and just make sure that uh you attempt it uh with with whole heart and I hope that uh that is going to add up something more into your preparation. So guys, I'm not going to take much time of yours. I've I've been eating your head from last almost four or five hours. I'm sure you must be hungry for your lunch and I'm take a bow. Thank you so much and do send me your messages on my Telegram. You all know that about Telegram, my inbox and wherever you can. Your feedbacks is is the is is the most desirable thing that that I want from you. Thank you so much. It's 2:33 a.m. in Calgary. The temperature outside is 10 degrees. It's pretty cozy. And uh once again, thank you so much for staying with me for so long and attending this session. Goodbye. Take care. God bless you all.

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Anatomy Revision for NEET PG 2025 | DBMCI One Shot 3.0 | Day 8 | Dr. Ashwani Kumar

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