 This is a demonstration of the pectoral muscles and the triangles which are related to the pectoral muscles. This is a supine cadaver, not standing on the right side of the cadaver. Cara person is also on the right side towards the head end. This is the right pectoral region. This muscle that we can see in front of us, this is the pectoralis major muscle. We have retained a little bit of the deep fascia and we have reflected it up now. The pectoralis major has got two components. First is this component that we can see here. This is known as the clavicular head of the pectoralis major. And this takes origin from the clavicle as we can clearly see here. The other component of the pectoralis major, the larger one, is this from here all the way here. This is the sternocostal head of the pectoralis major. And this takes origin from the sternum and the related ribs, that's why it's called the sternocostal head. The lower fibres they inter-digitate with and take origin from the aponeurosis of the external oblique muscle of the abdomen. So this is the origin of the sternocostal head. Both the sets of fibres they converge as we can clearly see here. And here they do a very interesting thing. The fibres from the clavicular head, they are superficial. The fibres from the sternocostal head, they are deep. That means the fibres have pristed and we can see here when I lift up one part of it. The deeper fibres have gone deep. This twisting makes it occupy a smaller space and finally the tendon gets inserted onto this region here. This is the lateral lip of the inter tubercular sulcus. Action of the pectoralis major. Adduction, medial rotation. The clavicular head is responsible for flexion of the arm. And the sternocostal head extends the arm from the flex position. So these are the basic actions of the pectoralis major. Nerve supply of the pectoralis major. Lateral pectoral nerve and medial pectoral nerve, which I shall show you just now. A few other points about the pectoralis major. The pectoralis major forms a boundary, a groove between the pectoralis major and the deltoid muscle. And this is that groove. And this is referred to as the delto pectoral groove. And running in the delto pectoral groove is this structure which I have picked up. This is the cephalic vein, which is a very important superficial vein in every person. So this is one important relationship. Next, if we continue the delto pectoral groove above, we see that it widens into a triangle. This is the delto pectoral or the clavipectoral triangle. Again, this is bounded by the pectoralis major, the deltoid and the clavicle. The root of this triangle is by a membrane, by a fascia called the costocoroboid membrane. And this triangle is pierced by three important structures and a fourth one. And they are visible here. This is the same cephalic vein, which pierces the costocoroboid membrane and opens into the axillary vein. Second structure which pierces is this. This is the thoracocromial artery, which is the branch from the second part of the axillary artery. And this then, after emerging, it divides into four other subdivisions. And a few of those we can see here, namely a pectoral branch, deltoid branch, clavicular branch and acromial branch. The third structure which pierces is the lateral pectoral nerve. And we can see part of that here. This is the one which pierces the costocoroboid membrane and it supplies the pectoralis major. The pectoralis minor, which I'm going to show just under this, is under the medial pectoral nerve, which pierces the pectoralis minor and then supplies the pectoralis major. So that is another important relationship of the pectoralis major. The third important relationship of the pectoralis major is, when I put my hand in, you can see my hand is gone behind the pectoralis major. The pectoralis major forms the anterior wall and the anterior fold of the axilla and we can feel it in our own cell. So this is the anterior fold of the axilla. And we can feel it by tightening the pectoralis major when we ask the patient to hold his waist tightly with his hand and you can feel the muscle standing up. So this forms the anterior pectoral line. This is the pectoral anterior fold of axilla. This is a femal cadaver. So therefore, there is a breast here, which we can see. There is a loose aerial tissue layer, which we have dissected through, between the pectoralis major and the breast. And that loose aerial tissue layer is referred to as the retro mammary space. This retro mammary space enables us to dissect during mastectomy. And the same retro mammary space, which is in front of the pectoralis major, is also used by plastic surgeons for breast augmentation procedures. I would like to draw your attention to these structures which are piercing the intercostal spaces on the medial side. And I have picked up several of them. These are the anterior cutaneous branches of the intercostal nerves. And accompanying them are the perforative branches of the internal thoracic artery, especially in the second, third and fourth space. They are very significant, especially in females. And they are referred to as the perforating branches, which supply the medial mammary arteries to the breast. And therefore, during mastectomy, they have to be meticulously ligated and cut during mastectomy. So that is about the perforating branches, which supply the medial mammary arteries. Now, I have already cut the pectoralis major here. I am going to reflect it to show a few other salient points. So, this is the distal portion of the pectoralis major. I am reflecting and this is the proximal portion of the pectoralis major, which I am reflecting. When we reflect, we can see several things. First of all, let's come back to something which I mentioned in the beginning. We can see that the inserting fibres have become double layered. These fibres are the ones which came from the clavicular head. And these fibres are the ones which came from the sternocostal head. And we can see them forming a curve. In some patients, between the superficial and the deep fibres of the pectoralis major and the point of insertion, there may be a burst. That is one thing I would like you to notice. The next thing is, you see a thin layer of fascia that we have retained here. This is the fascia which covers the pectoralis minor muscle, which we will reflect now. And we can see that these are the branches of the lateral nerve, which are piercing through the pectoralis minor, piercing through the pectoralis minor and then supplying the pectoralis major. On the other hand, the lateral pectoral nerve pierces the crostocorochoid membrane and directly supplies the pectoralis major. These are the branches of the lateral pectoral nerve. Some plastic surgeons have also done breast augmentation surgery by putting the prosthesis under the pectoralis major, where my finger is located, the sub pectoral prosthesis with variable results. Now that we have reflected the pectoralis major, we can see yet another muscle under that. And this is the pectoralis minor. The pectoralis minor takes origin from the third, fourth and fifth ribs. In this case, there is a variation. Fibres are originating from the second rib, the third rib and the fourth rib. And they get inserted where my finger is going. This is the insertion and this is the corocate process. So this is the pectoralis minor. What is the action of the pectoralis minor? It helps to protract the shoulder. That means bring the shoulder forward. And also it helps to stabilize the scapula during movements of the pectoral girdle. If you look at the pectoralis minor, we can see that this was covered by a thin glacier here on the front, which we have reflected up. And on the under surface also, there is a layer of fascia. So that is the pectoralis minor fascia, covered both anteriorly and posteriorly. This same fascia, both the layers then fuse at the lower margin of the pectoralis minor and we can see a little bit of the remnant of that. And this then continues and we have cut it. It continues down and becomes what is known as the suspense tree ligament of the axilla. And that gets attached to the axillary fascia. And this is the one which is responsible for producing the fold of the axilla, where my finger is located, when we raise our arm. This is the suspense tree ligament attached to the axillary fascia. If you look at the upper margin, we can see a little bit of the remnant of the costocorochoid membrane, which forms a flow of the fempectro trang. And now that we have reflected the pectoralis major, we can more clearly see this is the cephalic vein opening into the axillary vein. The thoracochromial artery and we can also see the branches of the lateral pectoral nerve. This costocorochoid membrane also appears by lymphatics. In between the pectoralis major and the pectoralis minor, there is a group of lymph nodes which are referred to as the interpectoral nodes or the daughter's nodes. And some of them pierce through the costocorochoid membrane and they enter into the axilla. The pectoralis minor, if you notice, it forms a bridge here where my finger is gone in. And this is an important anatomical and surgical landmark. The pectoralis minor divides the structures inside the axilla, especially the axillary artery, into three parts. The portion which is proximal to the pectoralis minor, from the first rib to the pectoralis minor, that is known as the first part of the axillary artery. The portion which is behind the pectoralis minor is referred to as the second part. And the portion which comes from the lateral border of the pectoralis minor to the lower border of the teres major, which you cannot see, that is known as the third part of the axillary artery. The same pectoralis minor also helps to divide the groups of lymph nodes in the axilla. Those lymph nodes which are in relation to the second part of the axillary vein where my finger is located, they are referred to as the central group of lymph nodes or the level two lymph nodes in surgical parlance. Lymph nodes below that are level one and lymph nodes above that are level three lymph nodes. So therefore, the pectoralis minor bridge forms a very important landmark. The pectoralis minor also forms the anterior wall of the axilla. So these are some of the salient points about the pectoralis minor. The pectoralis minor we can see is being pierced by these nerves. These are the branches of the medial pectoral nerve which pierce through the pectoralis minor and then supply the pectoralis major muscle. So these are some of the points about the pectoralis minor and the pectoralis major, cleavage pectoral fascia and the delta pectoral triangle. Thank you very much for watching. If you have any questions or comments, please put them in the comment section below. Dr. Sanjay Sanyal signing out. Have a nice day.