 are as usual Jeanne Glover, Zilliqa Stewart and Saha. Today we are going to, by the way my name is Dr. Sanjay Sanyal. I'm the Professor and Department Chair of Anatmical Sciences. The first part of this video is I'm going to demonstrate the muscles of the anterior pectoral region. So what you see in front of you here, this is the pectoralis major muscle. The pectoralis major has got two parts. This portion that you see here, this is called the sternocostal part because it takes origin from the sternum and the costal cartilages and it also takes origin from the aponeurosis of the external oblique muscles of the abdomen. And the other part of the pectoralis major is this portion here which takes origin from the clavicle. This is called the clavicular part. Both these parts, the fibers they merge, they converge and form a narrow attachment. And at the point of attachment the fibers they rotate and sometimes there's also a bursa in between the rotating fibers. And the finally all the fibers they get inserted onto the lateral lip of the intertubicular sulcus. So this is the pectoralis major. The sternocostal head, this is responsible for adduction and medial rotation of the arm. And the clavicular head is responsible for flexion of the arm. Flexion of the arm is at an angle to the trunk. So these are the pectoralis major. Now let's do something. We have removed the origin of the sternocostal head and so let me reflect the sternocostal head. And concomitantly I have also reflected the clavicular head which you can see here. And once we have done that what do we notice? We notice yet another muscle under the pectoralis major and this is the pectoralis minor. Where does the pectoralis minor extend from? It originates from the coracoid process here. It bridges across the axilla and it gets inserted into the third, fourth and fifth ribs. So this is the pectoralis minor. The pectoralis minor though it's a very small muscle it forms a very important landmark when we come to the parts of the axilla especially the parts of the axillary artery and it bridges over the axilla. If you'd look closely above the pectoralis minor this gap here this was in life this was filled by a membrane which is a part of the clavipectoral fascia and this portion of the clavipectoral fascia has got a separate name it was called it is called the costocorochoid membrane and this costocorochoid membrane is located in the delto pectoral triangle. Why is it called the delto pectoral triangle? Because when I put the arm in the anatomical position it's a triangle which is between the deltoid the pectoral muscle and the clavicle the delto pectoral triangle and the floor of that is formed by the coracoid costocorochoid membrane and it is roofed over by the clavicular head of the pectoralis major. This delto costocorochoid membrane which forms a flow of the delto pectoral triangle is pierced by the cephalic vein which you can see a little bit starting from here. This is the cephalic vein it goes all the way in the delto pectoral groove and it goes in the delto pectoral triangle and it enters into the axilla by piercing through the costocorochoid membrane and opens into the axillary vein but that has been removed here. Other structures which pierce the costocorochoid membrane are a branch of the axillary artery called the thoracoacromial artery. It is also pierced by the lateral pectoral nerve which supplies the pectoralis major muscle and it is also pierced by lymphatics. So this is the location of the delto pectoral triangle which is covered by the costocorochoid membrane and finally before I get out of this video let me show you the next muscle which is visible here. This muscle that you see here this is the deltoid muscle. The deltoid is a muscle which gives you the rounded appearance of the shoulder. It has got four three groups of fibers the anterior group the middle group and the posterior group is here which has not been dissected out and all of these three groups they converge here and they get inserted onto the deltoid tuberosity of the human or the lateral aspect of the humerus. The deltoid muscle is supplied by the axillary nerve and it pierces it supplies the nerve the artery in the the muscle from deep inside and after it is supplied the deltoid muscle the nerve comes out and it supplies a skin in this region of the arm. This is an important clinical point if there's an injury to the axillary nerve then not only is the deltoid muscle paralyzed but there's also a patch of venesthesia on the upper lateral aspect of the arm which is located shown by my index finger. What is the action of the deltoid muscle? The anterior fibers of the deltoid they are useful when we are walking when we are swinging arms forward and backwards. The anterior fibers are responsible for flexion of the arm the posterior fibers are responsible for extension of the arm and when we are abducting our arm from beyond 15 degrees to 90 degrees then the anterior and the posterior fibers they neutralize their actions and only the middle fibers are responsible for abducting the arm from 15 to 90 degrees. The deltoid muscle has got isotonic metric contraction isotonic concentric contraction and isotonic eccentric contraction that is when we are bringing your arm from an abducted position to the abducted position. So for the for this video these are the muscles which i shall show you the subsequent video i'm going to show you the muscles of the arm but right now thank you very much for watching ladies and gentlemen have a nice day don't forget to sign your signing out signing out