 Welcome to the next section, Muscles of the Anti-Apectral Girl. I'm Dr. Sanjay Sanyal, Professor and Department Chair of the Natypical Sciences in the Caribbean. So, in this specimen, what we have done, this was a female canaver, so therefore we had to do a total mastectomy. The breast was removed in the surgical plane between the breast and the pectoralis major through what is known as the retromammary space, and therefore that specimen has been removed here. Once we do that, what do we notice? Straight away, we notice a muscle in front of us. This muscle is the pectoralis major muscle. Incidentally, before I tell you about the parts of the pectoralis major and all the other aspects of it, these are some of the fibers which were interdigitating and taking origin from the fibers of the external oblique muscle of the aponeurosis of the abdomen, and which I have cut and I am reflecting away. So, we notice that the pectoralis major has got an extensive origin all over the front of the chest wall, the so-called pecs of people who do workouts. This portion of the pectoralis major, which is referred to as the sternocostal head, and this portion, which is attached to the clavicle, is referred to as the clavicular head. Both these portions, they unite laterally, and the fibers, they rotate by 90 degrees, and then they get inserted onto the lateral lip of the intertubercular sulcus of the arm. And when they rotate, there is quite often a bursa located between the two portions of the rotated fibers. What do the sternocostal head do? The sternocostal head is responsible for adduction and medial rotation, while the clavicular head is responsible for flexion of the arm. The sternocostal head brings the arm back from the flex position. Okay. If you notice, the pectoralis major forms the anterior boundary, anterior fold of the axilla. It also forms the anterior boundary of the axilla, by the way. Which we shall tell when we come to the axilla. Now what I will do is I will reflect. I have already incised the attachment of the sternocostal head and the clavicular head, and I am reflecting the sternocostal head. When I reflect the sternocostal head and the clavicular head, we notice a nerve. This is the medial pectoral nerve. But more about the nerve a little later. Under the sternocostal head we notice yet another muscle. This is the pectoralis minor. It takes origin from the third, fourth and fifth ribs, and the fibers move upwards and laterally, and they get inserted onto the coracoid process. And what does the pectoralis minor do? The pectoralis minor helps to bring the scapula downward and inferiorly and also helps to stabilize the scapula during movements of the pectoral gird. Coming back to this nerve, this is the medial pectoral nerve. It supplies the pectoralis minor. It pierces through the pectoralis minor and supplies the pectoralis major. Now let me put back this muscle in its place, and the clavicular head in its place. This is the boundary of the pectoralis major, and this is the margin of the deltoid muscle. In between we see a shallow groove here. This is the delto pectoral groove, and running in the delto pectoral groove, we can see a very prominent nerve, a vein. This vein is the cephalic vein. It's a very important vein, and we can see this especially in thin persons or in muscular people as a vein running on the lateral aspect of the arm. This runs in the delto pectoral groove, and as it goes up, it enters a triangular space. This triangular space is referred to as the delto pectoral triangle. It also is referred to as the clavy pectoral triangle. And as the term implies, it is bounded by the lateral part of the clavicle, by the pectoralis major, and the deltoid. The flow of this triangle is formed by a membrane called the clavipectoral membrane or clavipectoral fascia. It is also called the costocorochoid membrane. And this cephalic vein pierces through the costocorochoid membrane, and it enters into the axilla where it meets with the axillary vein, which I shall tell you later on. Also piercing the clavipectoral fascia of the costocorochoid membrane is this nerve. This is the lateral pectoral nerve, which supplies the pectoralis major alone. Okay, having mentioned that, now let me reflect out the clavicular head to show you yet one more muscle, which is located deep inside. It's a very small muscle. It starts from the first costocontal junction here, and it moves upwards and gets inserted onto the subclavian vein, the subclavian groove of the clavicle. This small muscle is the subclavius muscle. Subclavius muscle, it is supplied by the nerve of the subclavius, and the action of this is to pull the clavicle downwards and inferiorly and stabilize the clavicle during movements of the pectoral girdle. So this, what we have seen right now is the pectoralis major, the pectoralis minor, the subclavius muscle, delta pectoral groove, and the clavipectoral triangle. Before I conclude, I need to mention one more point about the pectoralis minor, though I'll elaborate upon it when we talk about the axilla. The pectoralis minor forms an important landmark in dividing the axillary artery, axillary vein into three parts, part one, part two, and part three. It also helps to demarcate the axillary lymph nodes into what is known as the central group of lymph nodes which are located right behind the pectoralis minor where my finger has gone in. But we shall talk more about this when we come to the axilla. That is all for today, ladies and gentlemen. Thank you very much for watching. 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