Transcription
[Music] [Music]
Hello everyone. Hope you're all doing well.
Now we are going to discuss the topic on anterior abdominal wall. First, what are the layers of anterior abdominal wall? The layers include number one, it's the skin, what we see first. Then comes the subcutaneous layer. Then it is the superficial fascia. Then comes the muscles, namely external oblique, internal oblique, transversus abdominis, transversalis fascia, extraperitoneal fat, and the peritoneum.
Okay, we'll see this in the picture for better understanding. So this is the skin. Immediately down to this, you'll have the subcutaneous tissue, and these are the fascia. Two layers of fascia, superficial fascia. You have one is the Camper's fascia here, down and down to that, you'll have the Scarpa's fascia. Then you will have the muscles and their respective fascia. Then you will have the transversalis fascia, extraperitoneal fat, and below that, you will have the parietal peritoneum.
Now, we'll go one by one. First point you have to know about the skin. In skin, only one point you have to know here. The dermal fibers are oriented transversally. Right? And this orientation of dermal fibers in a transverse manner is known as Langer's line. Yes. So this is important.
Next comes the subcutaneous layer. In the subcutaneous layer, you have one superficial fatty layer and another deep membranous layer. This superficial fatty layer is known as Camper's fascia, and this deep membranous layer is known as Scarpa's fascia. Now, the superficial fatty layer is not present only in the abdomen. It also extends onto the perineum to give fatty substance to the mons pubis as well as the labia majora. Paris. This Scarpa's fascia will go down to the perineum and be called as fascia.
Now, muscles of the anterior abdominal wall. We can divide it into two groups. First group is the flat muscles, and the next group is the vertical muscles. The flat muscle group consists of three muscles, namely the external oblique, the internal oblique, and transversus abdominis. In the vertical group, we have the rectus muscle and the pyramidalis.
Now, coming to the first muscle, that is the external oblique. External oblique is the largest and the most superficial muscle you will see in the anterior abdominal wall. How the fibers are oriented in the external oblique? Are these fibers are oriented by passing downwards and forwards, just like how you, if you leave your hands into your pocket, how your hands will be directing? It will be directing downwards and forwards. So that's how the fibers of this muscle also is oriented. Then the origin of the muscle is from the lower eight ribs. And these muscles are inserted into the linea alba, pubic tubercle, and the outer half of the iliac crest.
Coming to the next muscle, that is internal oblique. Internal oblique is the intermediate muscle that you will see in the flat muscle group. This fibers of the muscle are oriented forwards and upwards, just they are placed in a right-angled manner to the external oblique muscle fibers. And origin of the internal oblique muscle is from the thoracolumbar fascia, anterior two-thirds of the iliac crest, and lateral third of the inguinal ligament. Where are these inserted? This muscle is inserted into the pectineal pubis and the linea alba.
We'll see the next muscle. We'll see the next muscle. Transversus abdominis. As the name says, this transversus abdominis, the fibers run transversely, and this is the innermost muscle of the flat muscle group. The origin of the muscle lies from the thoracolumbar fascia, iliac crest, lateral third of the inguinal ligament. This muscle is inserted into the linea alba, pectineal pubis. Sorry, repeat. This muscle is inserted into the linea alba, pubic tubercle, and transversus abdominis muscle aponeurosis along with the internal oblique muscle aponeurosis will be together forming the conjoint tendon. So this is how the muscle is getting inserted into the linea alba under the pubic crest.
These are the muscles we have discussed so far. It is the external oblique muscle, internal oblique muscle, and the transversus abdominis. So external oblique muscle fibers pass downwards and forwards. Here, internal oblique muscle fibers are passing upwards and forwards. Then transversus abdominis muscle. See the orientation of the fibers are running transversely. And in the next picture, this conjoint tendon, that is the joining of the aponeuroses of internal oblique and transversus abdominis muscle. See here, here we have the transversus abdominis. Here we have the internal oblique. So here is the conjoint tendon where the aponeuroses of both muscles are joining together and getting inserted. Right.
Next, we'll come to the vertical muscle group. In that, we have two muscles. Number one is rectus abdominis, and two is pyramidalis. Coming to rectus abdominis. This is the principal muscle in the vertical group. And you have three tendinous inscriptions within each rectus abdominis. Like, if I show the picture, you will see this is the picture of the rectus abdominis. So you're able to see three tendinous inscriptions. This is the first one. Three tendinous inscriptions within each muscle. Three tendinous inscriptions are present. Origin of the muscle is from the pubic symphysis and the pubic crest, and the muscle gets inserted into the xiphoid process of the fifth, sixth, and the seventh costal cartilages. So origin is from the pubic symphysis and pubic crest, inserted into the xiphoid process and fifth, sixth, seventh costal cartilages.
Next comes the pyramidalis muscle. Pyramidalis muscle is located. This is the portion of the pyramidalis muscle. This muscle is a triangular-shaped muscle. And if you see, it is located in the inferior part of the rectus abdominis. And pyramidalis muscle is absent in approximately 20% of the population. The origin of the muscle is from the pubic symphysis, and it is inserted into the linea alba, the anterior surface of the pubis, and the pubic ligament.
Now, as we have completed the muscles, we are going to discuss about one important structure in the anterior abdominal wall, that is the rectus sheath. Rectus sheath is a dense regular connective tissue. It is formed by the aponeuroses of the flat muscles. Now, tell me, what are the flat muscles? It is the external oblique, internal oblique, and transversus abdominis. Right?
Now, the rectus sheath, how it is formed? We have the anterior layer and we have the posterior layer. Anterior layer of rectus sheath is formed by the aponeurosis of the external oblique and the internal oblique. Aponeurosis comes here and it divides into the anterior leaf and a posterior leaf. Right? Then it will enclose the rectus abdominis muscle. And then comes a marking. This will call as arcuate line. Below the arcuate line, what happens is the external oblique aponeurosis passes like this, but the internal oblique aponeuroses are going to combine together and pass above the rectus muscle. And then the transversalis fascia is going to pass down like this. Anyhow, the muscle is going to be this much size. Can you understand?
So, what I'm trying to explain is, above the arcuate line, what I'm trying to explain is the anterior layer of the rectus sheath is formed by the aponeurosis of the external oblique and anterior leaf of the aponeurosis of the internal oblique. And below and downwards, above the arcuate line, you have the posterior leaf of the internal oblique and the transversalis fascia. But when you come below the arcuate line, the rectus muscle lies directly on the transversalis fascia because the internal oblique aponeuroses combines together and it passes anteriorly above the rectus muscle. Understood? So this one point is important.
So this is how the aponeuroses will combine together and form the rectus sheath. And these are the panels of muscle that make up each of the abdominis. Rectus abdominis muscle. So this is what is basically you see as six packs.
Now, we'll see the diagrammatic representation of my explanation. So we have the skin, we have the subcutaneous fat, the external oblique muscle is there, and the internal oblique muscle, and the transverse abdominis. What happens is the external oblique muscle aponeurosis is coming here. Internal oblique muscle is coming, and it is getting split down, and transversus abdominis muscle fascia is coming down. So this is above the arcuate line. Okay, this is above the arcuate line. What is happening is it is being surrounded on both the sides. The muscle is surrounded on both the sides. But below the arcuate line, once you come, all these aponeuroses are joining together and they are passing above the muscle. And here, if you see, the muscle directly lies on the transversalis fascia.
Also, you have to know about the linea alba. Linea alba is the thickening of the rectus muscle sheath that extends from the xiphoid process to the pubic symphysis.
Now, what are the contents of the rectus sheath? As we all know, it has two muscles, namely rectus abdominis and pyramidalis. Then it will have vessels, namely superficial epigastric vessels. Then it will have some lymphatics. Then it will have lower intercostal thoracic nerves.
Now, what is the blood supply of the anterior abdominal wall? It mainly comes from the branches of the femoral artery. Three branches, especially. Number one is superficial epigastric artery. Then superficial external pudendal artery, and superficial circumflex iliac artery. Now, this branches of femoral artery supplies the skin and the subcutaneous layers of the anterior abdominal wall, including the mons pubis. Okay, it extends up to the mons pubis.
Next, we have the branches of the external iliac vessels. Branches of external iliac vessels include inferior epigastric artery on both the sides, as well as the veins that will supply the anterior abdominal wall and the fascia. It is bilateral inferior epigastric vessels, which are the branches of the external iliac vessels.
Now, coming to the nerve supply. Nerve. Now, we'll come to the nerve supply. Nerve supply comes from the anterior rami of lumbar nerves that include iliohypogastric nerves and ilioinguinal nerves, whose root value is L1. And these nerves are mostly sensory nerves. Also from the anterior rami of thoracic spinal nerves, you will get intercostal nerves and subcostal nerves, whose root value is between T7 to T11 and T12. This intercostal and subcostal nerves will lie in a plane called as transversus abdominis plane. This plane is seen between the two muscles, namely the transversus abdominis and the internal oblique.
Now, we are going to see about the umbilicus. As we all know, umbilicus contains the umbilical ring where the fetal vessels have passed through during the fetal life, and it is surrounded by the skin, transversalis fascia, and the peritoneum. From the parietal peritoneum, three attachments are present that is seen extending to the umbilicus. Number one is the median umbilical ligament, which is a remnant of urachus. This urachus is a fibrous tissue that is seen in fetal life extending from the apex of the bladder to the umbilicus. Then you'll have the medial umbilical ligaments, which are the remnants of umbilical arteries that is seen bilaterally. Then comes the lateral umbilical ligaments that will contain the patent inferior epigastric vessels. Nerve supply of umbilicus, just like how it is seen round. So it is T10 dermatome.
Okay, we'll see the SP for better explanation. So you have the anterior abdominal wall internal view over here. So you have the peritoneal membrane. This is where you have the umbilicus. You have the medial umbilical fold, the center pink one, what I'm drawing. And then comes the medial umbilical fold like this on both the sides. Then comes the lateral umbilical fold. Okay. So these are the lateral umbilical folds. Okay.
Now, you will be wondering why, ma'am, you are teaching anterior abdominal wall in obstetrics and gynecology? Because during surgeries, this anatomy of anterior abdominal wall, its blood supply, and the muscles, rectus sheath, everything is very important. So we'll see the clinical significance also. Some of the clinical significance, starting from the skin, we have seen the dermal fibers are passing along Langer's line. So when you give a transverse incision, there are better cosmetic results than giving a vertical incision. Then you have to be very careful while entering the anterior abdominal wall because you're going to encounter vessels like superior epigastric vessels and the inferior epigastric vessels, which if not cauterized properly can lead to excessive hemorrhage and blood loss.
Next one, we have seen the transversus abdominis plane. So in this region, we can give post-cesarean blockade to get pain relief. We also have the ilioinguinal and iliohypogastric nerves. If these nerves are severed during surgery, it will lead to loss of sensation in the area in which these nerves will supply.
We have finished the topic on anterior abdominal wall. Until we meet in the next video, take care and bye-bye.