Transcription
So guys, in this section, we will talk about the blood vessels of the upper limb. And the way we'll approach is that we'll start with the blood vessels in the auxiliary region. So, that we'll talk about the auxiliary artery. Then we will talk about the anastomosis around the scapula, which is between the auxiliary artery and the subclavian. We'll proceed to the brachial artery. We'll talk about the major branches of the brachial artery. We will also see how the brachial artery, along with its branches like the radial artery, forms an anastomosis at the elbow. Elbow anastomosis. We will also see the distal course of the radial artery in the hand and how they help in the formation of superficial and deep palmar arches. I'll keep showing you some images also in between.
So let us first start with the axillary artery. Now, the axillary artery is divided into three parts by a muscle which is crossing in front of it, and the muscle is pectoralis minor muscle. So let's imagine this here is a coracoid process. Coracoid process is the process on which the pectoralis minor muscle will insert. And here we have this muscle that is pectoralis minor muscle. Just highlight that for you. This is pectoralis minor, and passing deep to the pectoralis minor, we've got the axillary artery, which is divided into three parts because of this muscle only. So here we have this is the axillary artery. Let's say, as we know that the axillary artery starts from the outer border of the first rib, that is where the subclavian artery ends and the axillary artery begins.
Now, this here is the first part of the axillary artery, which is proximal to the pectoralis minor. Here we've got the second part of the axillary artery, which is deep to the muscle. And the third part of the axillary artery is distal to the muscle. So we've got one, two, and three parts. And the branches of the axillary artery can also be easily remembered with the same one, two, three sequence only, because the first part of the axillary artery will give one branch, the second part will give two branches, and the third part will give three branches.
So guys, the only branch coming from the first part of the axillary artery is called as the superior thoracic artery. There's a superior thoracic artery, and that is the only branch coming from the first part of the axillary. Two branches from the second part. That means both these arteries are starting deep to the muscle itself. So, one of the artery here, which runs deep to this muscle and then emerges at the lower border of pectoralis minor, the artery is called as the lateral thoracic artery. This is the lateral thoracic artery. It is also one of the major arteries supplying the mammary gland. Although the mammary gland is mainly supplied by the internal thoracic artery, also called as internal mammary artery, coming from, uh, the subclavian. But yes, we can say lateral thoracic artery is also having a good contribution to the mammary gland here. So, as you can see, the artery is going deep to the muscle first and then running along the lower border of pectoralis minor.
We also have another artery which is originating behind this muscle itself and then emerging from the upper border and subsequently dividing into four more branches. This artery here is called as the thoracoacromial trunk. That's the second artery we're talking about from the second part, guys. There is the thoracoacromial trunk. It's a trunk. This thoracic trunk or thoracic artery is further going to divide into four branches. And those four branches can be remembered as A, P, C, and D. Not ABCD. A, B, C, D is the right way to remember it. So, four branches of the thoracoacromial trunk. Let me write it for you. A stands for the acromial branch. A is for the acromial branch. So you will see a branch of this artery going toward the acromial process. P stands for the pectoral branch. Pectoral branch also supplies the mammary gland and the pectoral muscle, that is the pectoral branch. C is for the clavicular branch. C is the clavicular branch. And D is the deltoid branch of the thoracoacromial trunk. So when this trunk comes out, it pierces up the fascia here called as the clavipectoral fascia and divides into the four branches, that is acromial branch, then we have a pectoral branch, we've got a clavicular branch, and we've got a deltoid branch. So they're all running in different directions and supplying the respective structures.
So, one artery from the first part, and we saw two arteries from the second part. One is lateral thoracic, and one is thoracoacromial trunk. Now, coming to the third part of the axillary artery. This third part is very close to the surgical neck of the humerus. And that's why the branches are also in accordance. So guys, let us say if this here is the shaft of the humerus, just presume it is a shaft of the humerus here, the surgical neck and the shaft of the humerus. So what you'll see from the third part, we have three branches. Number one, we have a branch which is the largest branch of the axillary artery. I'll tell you about its name. And then we have two more branches slightly more distal to it. One winds anteriorly to the surgical neck of the humerus, and another one winds posteriorly to the surgical neck of the humerus. What arteries are these? Well, this artery which is winding posteriorly here, this here is called as posterior circumflex humeral artery. I'm writing in short, PCHA, posterior circumflex humeral artery. Whereas the one which is winding in front of the surgical neck of the humerus is the anterior circumflex humeral artery. So PCHA and ACA are the two branches here. And then we said the largest branch of the axillary artery is also coming from the third part. And this is the one I was talking about. This is the subscapular artery. This artery here is the subscapular artery here. Let me just quickly recap it for you.
So, what we said that from the first part, we have only one branch, and that only branch was superior thoracic artery. Done. Second part, we said we got two branches here. One is thoracoacromial trunk, which you can see further dividing into four branches, and also the lateral thoracic artery. You can see they are coming out of the upper border and the lower border of pectoralis minor muscle respectively. Third part, three branches. Third part, three branches. Subscapular artery being the largest branch. I'll tell you more about it. And then we have the two arteries which are winding around the surgical neck of the humerus, that is ACA and PCHA, an anterior circumflex humeral artery and posterior circumflex humeral artery. So, one branch from the second, first part, sorry, two branches from the second part, and three branches from the third part of the axillary artery.
Whenever we talk about the blood vessels in the, whether it is in the upper limb or lower limb, one important thing that you must remember is if there is any nerve which is closely related to them, that makes it a very important surgical relation. Like there are two important nerves that we need to discuss here. A nerve that you see running behind the surgical neck of the humerus along with posterior circumflex humeral artery will be the axillary nerve. So guys, along with this PCHA, we've got the axillary nerve running in like this. I'm writing in short. This is axillary nerve. That's one very, very important relation. That axillary nerve runs along with the PCHA, along with the posterior circumflex artery. Second important relation is subscapular artery, guys. Along with subscapular artery, you will see a relation of the nerve, and this nerve here is the thoracodorsal nerve. This is the thoracodorsal nerve, also you can say nerve to latissimus dorsi. So, thoracodorsal nerve also can be called as nerve to latissimus dorsi. So, second important relation is along with subscapular artery, we have a thoracodorsal nerve or nerve to latissimus dorsi. It again is an important surgical relation here in the flap transfer of the latissimus dorsi. When you take a flap of latissimus dorsi, you take it along with the artery and the nerve, and you can see both of them running together here. Subscapular artery, apart from supplying the subscapularis muscle, it does supply latissimus dorsi, and thoracodorsal nerve, of course, it supplies latissimus dorsi.
Another important relation we said, axillary nerve along with PCHA. You know, if there is, if there is for any reason, if there is an injury to the axillary nerve, like if there is an inferior dislocation of the, uh, shoulder joint, or if there is an injury at the humerus at the level of surgical neck of humerus on the posterior aspect, then not only axillary nerve, even the posterior circumflex humeral artery can be compromised. So, first thing first, guys, these are the branches from the axillary artery. Remember one thing. I mean, let's not spoil our diagram for this. Axillary vein will be seen running along with the axillary artery throughout its course on its medial side. So, whether it is first part, second part, or third part, axillary vein is present on its medial side. I would recommend you not to draw it. I'm just doing it for your orientation's sake. Like this, axillary vein will be running in this manner. Just, just keep it in mind that one constant medial relation of the axillary artery will be the axillary vein.
And you know, people do have a little difficulty in remembering the relations of the axillary artery. And I would say that the easiest way to remember the relation of the axillary artery is they think about the brachial plexus. When you think about the cords of the brachial plexus, the cords are obviously the more distal part of the brachial plexus, right? And those cords are related to the third part of the axillary artery. The nomenclature of the cords in the brachial plexus is based on the relation to the axillary artery only. Like, lateral cord of the brachial plexus is lateral to this part. Medial cord is medial to this part. And posterior cord is posterior to this third part of the axillary artery. So guys, if you're thinking about the relation of the axillary artery, third part relations are very, very simple. Think about the branches coming from the lateral cord of the brachial plexus. They will be forming the lateral relation, like musculocutaneous nerve is there, right? Then think about the posterior cord of the brachial plexus. Posterior cord is having the branches like what? Like radial nerve. It is also having the branches like axillary nerve. They are obviously the posterior relation. Medial cord of the brachial plexus, nerve like ulnar nerve, medial cutaneous nerve of arm, medial cutaneous nerve of forearm. They are all coming from the medial cord. Medial relation of the axillary artery. So don't try to mug up all these relations. It's pretty simple, and especially the third part relations. You just have to think about the cords of the brachial plexus and the branches coming out from the cords of the brachial plexus, and you can easily compare it.
Now, knowing these branches, first let me show you these branches on a picture, on an atlas image, and then we will talk about the anastomosis around the scapula. So here we have an atlas image in which we will discuss the same thing that we just saw. So, as you can see, the muscle over there is pectoralis minor. Let me just keep marking all these things. This is pectoralis minor muscle, and you can see pectoralis minor muscle is getting inserted to this coracoid process. So, this is the first part of the axillary artery. Deep to the muscle here, that is the second part. Here, and distal to the muscle here, we've got the third part of the axillary. You can see from the first part, very much in the beginning only, the artery coming out here is the superior thoracic artery. I'm just writing everything in short here. That is the superior thoracic artery. From the second part, as you can see, an artery coming along the lower border of pectoralis minor, this is lateral thoracic artery. And the one that you see which is emerging at the upper border and you can see dividing into four branches also, that is the thoracoacromial trunk. That's the thoracic trunk. Third part, look at the third part giving off this ACA, that is the anterior circumflex humeral artery, and the one which is behind that is the posterior circumflex humeral artery. And yes, this one here is the largest branch of axillary artery, we said, that is the subscapular artery. So, these are the branches coming from the three parts of axillary artery. Superior thoracic artery, we've got a thoracic trunk, and lateral thoracic artery from the second part. And third part, you can see the three branches coming out from there.
Okay. Now, what is why this topic is so important? The axillary artery and its branches, because the axillary artery is crossing a one very, very major joint, that is the shoulder joint. So, in case of dislocation of the shoulder, there are very good chances that this head of the humerus, it can compress the second part of the axillary artery. If there's a shoulder dislocation, there are chances that the head of the humerus will come forward and it can compress the second part of the axillary artery. So, if the second part of the axillary artery is compressed, then how the blood supply to the upper limb will be maintained? And that is where the anastomosis around the scapula comes into the picture, guys. Anastomosis around the scapula is an anastomosis between the first part of the subclavian artery. I'll tell you that, first part of the subclavian artery will be somewhere here, and the third part of the axillary artery. So that even if there is any obstruction anywhere here on the second part, or even in the first part, or even in the distal part of the subclavian artery, still the blood supply to the upper limb can be maintained. Let's talk about the topic, and then I will show you the picture for the scapular anastomosis.
So, we're talking about the anastomosis around the scapula. Now, practically, this scapular anastomosis, as I said, it is an anastomosis which is present between the first part of the subclavian, first part. It is present between the first part of the subclavian artery and the third part of the axillary artery, third part of the axillary artery. I'm not saying that there is no other contribution from any other part of the axillary artery, but yeah, it's mainly an anastomosis between the first part of the subclavian and the third part of the axillary artery. Now, before I draw this, I want you to narrow it down. We already discussed the subclavian artery in the head and neck region. Guys, subclavian artery, third part, first, second, third part, you know that the subclavian artery is divided by the muscle that is scalenus anterior muscle. Third part of the subclavian artery is having a branch. Uh, first part of the subclavian artery, I'm sorry, is having a branch. One is called as the vertebral artery. Now, vertebral artery is the one which goes above, goes into cranial cavity. So, forget about it. Another branch from the first part is the artery which is called as the, uh, thyrocervical trunk. Now, thyrocervical trunk is the one which supplies the, uh, what do you say? It supplies the thyroid gland. It gives like inferior thyroid artery. It gives off the suprascapular artery, and it gives off the transverse cervical artery and suprascapular artery. So, if you look at these names, like transverse cervical artery, it must be running somewhere transversely in the neck region. And the suprascapular artery, supra scapular. So, obviously, it is the one which is coming to the scapula here. So, that thyrocervical trunk from the first part of the subclavian artery is needed here. And we just saw the branches coming from the third part of the axillary. Let me put it together. Let's try to draw it, and then we'll discuss more detail of it.
So, let's presume this here is a scapula, right? So, we've got the axillary artery. We've got a first part of the axillary artery. Let me, first part of the subclavian artery, which is somewhere here. And continuing with that, if I reach in here, this is the third part of the axillary artery. I'm removing the middle part just to avoid any confusion. So, we have the first part of the subclavian, and then ultimately you're looking at a third part of the axillary artery below the branch that we said we need from the first part of the subclavian artery here is a thyrocervical trunk. Now, look at this, guys. Let's say this trunk here, this big trunk coming from here, is a thyrocervical trunk. Thyrocervical trunk. And just to clarify again, the thyrocervical trunk is coming from where? It is coming from the first part. First part of the subclavian artery. It is from the first part of the subclavian artery. What are the branches from the thyrocervical trunk? Now, one of the branches of the thyrocervical trunk is inferior thyroid artery. That has gone above and supplying the thyroid gland, not of concern here. The remaining two branches from the thyrocervical trunk are the one which, which are needed here, like one is called as suprascapular artery. Of course, the name says suprascapular artery is the one which will come like this from the suprascapular notch and will participate in the scapular anastomosis. And this suprascapular artery also gives off a branch toward the acromion process as well. We call it acromion branch. Let me mark that for you. This here is the suprascapular. That is the suprascapular artery. And as you can see, you can see the acromion branch of suprascapular artery is also there. Another branch here is the transverse cervical artery. Transverse, it's running transversely in the neck. So, guys, we call it a transverse cervical artery. And the transverse cervical artery, it further divides. We already discussed that in HNF. A transverse cervical artery, it divides into a superficial branch and a deep branch. The deep branch of transverse cervical artery, which is also called as dorsal scapular artery, will run along the medial border of the scapula. Look at that. And reaches all the way to the inferior angle. Yes, this is giving off numerous branches on the surface of the scapula also. So, what artery is that? This is the deep branch of transverse cervical artery. Either you simply call it deep branch of transverse cervical, or this is called as the dorsal scapular artery. Sometimes dorsal scapular artery comes from the third part of the subclavian also, that is a variation. But dorsal scapular artery usually is a name given to the deep branch of transverse cervical. So, guys, this is the contribution which is coming from where? From the first part of the subclavian. Let me repeat that again. We said what? Suprascapular artery. Number one. And second is a deep branch of transverse cervical, also called as dorsal scapular artery. Okay.
Now, it's time to look at the third part of the axillary artery. Now, you already know the branches from the third part of the axillary artery includes there is an anterior circumflex humeral artery and there is a posterior circumflex humeral artery. Let me go with that first. This is ACA, and this is PCHA, posterior circumflex humeral artery. Now, out of these two, the one which is participating in the anastomosis around the scapula is PCHA, not ACA. Remember, it's PCHA. Posterior circumflex humeral artery will also give off a branch which will go above toward the acromion process and participate in the anastomosis here. This again is called as an acromion branch. That, that is an acromion branch of suprascapular. And this is an acromion branch of posterior circumflex humeral artery. And we already discussed one acromion branch just now in the, in the previous discussion, we saw there's a branch from the second part of the axillary artery. What was the second part of the axillary artery? That was the thoracoacromial trunk. To the acromial trunk was giving four branches. A, B, C, D. A was what? Acromion branch. So, we have one more acromion branch. Let me put that here as. That acromion branch is coming from. This is the acromion branch of thoracoacromial trunk. Thoracoacromial trunk. So, there are three acromial branches you're looking at. And this anastomosis here, which is taking place at the acromion process, is called as an acromial anastomosis. This anastomosis, guys, is called as the acromial anastomosis. There is an acromial anastomosis. So, when we talk about the scapular anastomosis, there is one anastomosis which we are taking at the acromion. But before that, I'm looking at an anastomosis taking place at the acromion process by the three acromial branches from where? One from suprascapular. One acromial branch is from posterior circumflex humeral artery. And one acromial branch is coming from the second part of the axillary artery, that is from the thoracoacromial trunk. That's an acromial anastomosis.
Now, coming back to the body part. Now, what branches are participating in the anastomosis at the body here? Largest branch of axillary artery, we said, is subscapular artery. Now, look at this. If let's say this is a subscapular artery, it will be running along the lateral border and going down, anastomosing at the inferior angle. What artery is that? This is the subscapular artery. This artery here is the subscapular artery. And that's how there is an anastomosis which is formed at the inferior angle. Now, even this question can be asked that what arteries are anastomosing at the inferior angle? You can see that one is a dorsal scapular, or you can say deep branch of transverse cervical. And from this side, we have a suprascapular artery. They are anastomosing at the inferior angle, at the body. Well, this subscapular artery gives off a branch which winds around the lateral border of the scapula and then gives off numerous branches to anastomose with other branches on the body. Here, this artery, guys, is called as circumflex scapular artery. I'm just putting an asterisk sign over there. I'm writing it here. This artery is called as what? Circumflex scapular. Circumflex scapular artery, which is a branch of subscapular only. So, that's another anastomosis which is taking place in that region here, that is on the body. So, overall, I can say in detail that the anastomosis around the scapula can be divided into three parts. Anastomosis at the acromion process, anastomosis at the inferior angle of the scapula, and anastomosis at the body. You can see the body anastomosis is by what? Suprascapular is by the deep branch of transverse cervical, and also by the circumflex scapular artery. This is how we have a rich anastomosis around the around the scapular region. So, in case of there is a shoulder dislocation, if there is a compression of the second part of axillary artery, thankfully we have this anastomosis which can still maintain the circulation for the upper limb.
Now, time to see the same anastomosis in one of the atlas image. It's always good to keep looking into this atlas image so that later on, when you see the cadaver picture, you can easily correlate them here. Let me take you to that. So, we already saw these branches of the axillary artery, guys. Now, I'm taking you to this picture showing the anastomosis around the scapula. The difference is the diagram that we drew was considering the costal surface of the scapula, the anterior surface. Now, we are looking at the dorsal surface of the scapula. Doesn't matter. We can still easily identify it here. Now, look at this, guys. What branches I can appreciate in there? I can see from the first part of the subclavian artery. This here is the thoracoacromial trunk. I'm writing T8, that is thoracic trunk. And from this thoracic trunk, I can see this branch coming in here. This is the suprascapular artery. Okay. That, that here is the suprascapular artery. And I'm sure you can also see this acromion branch of suprascapular artery as well. I'm just writing AC, acromion branch of suprascapular artery, also going toward the acromion process. Suprascapular artery is coming down like this toward the body. But acromion branch is going toward the acromion process. Whereas this one here is the deep branch of transverse cervical artery. That is a deep branch of transverse cervical running along the medial border of the scapula all the way till inferior angle. Looking on the other side, because the view is from posterior side, that's a posterior view. So, this here is PCHA, posterior circumflex humeral artery. And you can see this branch coming from posterior circumflex humeral artery. Again, that's an acromion branch. That is an acromion branch. The two acromion branches are shown here in this. Look at the branch which you can see. I hope you can follow this pointer here. Look at this artery which is going down here. That is a subscapular artery, which will be running continue like this along the lateral border of the scapula till the inferior angle. So, this, this artery here is subscapular. This artery here is subscapular artery. But can you see this branch coming from subscapular and winding around the lateral border of the scapula? This is the circumflex scapular artery. That is the circumflex scapular artery. And that's how the anastomosis around the scapula is formed. So, I hope this picture clears, clears it up for you.
[clears throat] So, the anastomosis, a rich anastomosis between the first part of the subclavian to the third part of the axillary artery. And as I said already, that if there is a dislocation of the shoulder joint, this head of the humerus, even if it compresses the second part of the axillary artery, we still have other channels through which the collateral circulation can be maintained. Now, from here, let's move on further. So, we've done with the axillary artery. We've done with the anastomosis around the scapula, guys. Let me take you to this brachial artery and some branches of brachial artery, and then we will see that how it is forming a rich anastomosis around the elbow joint, called as an elbow anastomosis.