 session on muscles of the upper limb. In this session, we will be learning about the capylohumeral muscles. So, these are the list of muscles which we will be learning in this session. As the name suggests, they connect the scapula to the humerus. These are also referred to as muscles around the shoulder. So, these muscles are deltoid. Then, these four set of muscles, subscapularis, supraspinatus, infraspinatus and teresminus, these four muscles are included in rotator cuff. Rotator cuff of the shoulder also referred to as the musculotendinous cuff of the shoulder. And there is one more muscle, teres major muscle. So, these six muscles will be covering in this particular session. So, let us start with the deltoid muscle first. So, any muscle as you all know, when we study, we have to cover under particular headings. These are the headings. We should know the proximal attachment of the muscle, the distal attachment of the muscle, the nerve supply of the muscle and lastly, the actions of those muscles. So, for deltoid, proximal attachment is from three regions because there are fibers of the deltoid. This is the anterior fiber of deltoid. These are the middle fibers of deltoid. These are the posterior fibers of the deltoid. Since there are three different set of fibers, these three fibers originates from three different parts. The anterior fibers of the deltoid, they arise from the clavicle. The middle fibers of the deltoid, they arise from the lateral margin of the acromion. And the posterior fibers of the deltoid, they arise from the lower lip of the spine of the scapula. Then, distal attachment of the insertion of the deltoid is over the anterolateral surface of the humerus. There is a deltoid tuberosity which gives V-shaped attachment to the deltoid muscle. Then, nerve supply of deltoid muscle, nerve supply is by C5 and C6 final segments. The name of the nerve is axillary nerve. So, axillary nerve supplies deltoid muscle. There is one more muscle which is supplied by axillary nerve. That muscle is teres minus. Axillary nerve is is a branch from which part of the brachial plexus. It is a branch from the posterior cord of the brachial plexus. Then, actions of the deltoid muscle. Deltoid muscle is the chief abductor of the shoulder joint. 15 to 90 degrees of abduction of shoulder joint is done by deltoid muscle. 0 to 15 degrees is done by supraspinitis muscle. 15 to 90 degrees is done by deltoid and beyond 90 degrees it is done by the upper and the lower fibers of the trapezius acting along with the serratus anterior muscle. And the middle fibers of the deltoid, they are chiefly responsible for abduction of the shoulder joint. The middle fibers, there is a specific type of muscle fibers here which is referred to as multi-pinnet fibers. As the anterior and the posterior fibers of deltoid, those are unipinnet fibers. There are different actions for the anterior and the posterior fibers. The anterior fibers are responsible for flexion as well as medial rotation of the shoulder joint, whereas the posterior fibers are responsible for lateral rotation of the shoulder joint. So, whenever we speak about actions of the deltoid muscle, you have to speak about different actions of the different set of fibers of the deltoid. Abduction is chiefly done by the middle fibers of the deltoid. Now, let us look at some dissected images of the deltoid muscle. These are the anterior fibers of the deltoid. This is the middle fiber of the deltoid and in this image we are weaving the deltoid from the lateral aspect. Here these are the posterior fibers of the deltoid. This is middle and this is anterior. If we carefully look at the shape of the deltoid muscle, it is somewhat like this. It resembles an inverted Greek letter delta. That is why the name is deltoid muscle. And there is one important applied anatomy related to the deltoid muscle. The intramuscular injections are given in the deltoid muscle. It is most preferably given in the lower aspect of the deltoid muscle to avoid injury to the axillary nerve which finds around the surgical neck of the humerus. Now, let us cover the next muscle. The sub scapularis muscle. The proximal attachment of sub scapularis muscle is from the sub scapular posa. The anterior aspect of the scapula is the shallow depression which is referred to as sub scapular posa. The fibers go laterally to get attached here. The distal attachment is over the lesser tubercle of the humerus. Nerve supply of sub scapularis muscle is by the upper and the lower sub scapular nerve. Root value is C5 and C6 from the posterior cord of the brachial plexus. And actions of sub scapularis muscle is since the fibers are running like this and they are inserted over the lesser tubercle when this muscle contracts it will rotate the humerus medially. So, internet will lead to medial rotation of the shoulder joint. So, sub scapularis is the cheap medial rotator of the shoulder joint. Here we can see the dissected image of the sub scapularis muscle. This muscle is sub scapularis. Fibers arising from the sub scapular posa running laterally to get attached on to the lesser tubercle of the humerus and when this muscle contracts it will lead to medial rotation of the humerus in turn leading to the medial rotation of the shoulder joint. Now, let's cover the remaining four muscles. Supraspinatus, infraspinatus, pterisminus and pterismajor. All these four muscles have been along the posterior aspect of the scapula. The supraspinatus muscle it arises from the supraspinus posa. So, proximal attachment is from the supraspinus posa and distal attachment is over the greater tubercle of the humerus. In the greater tubercle of the humerus, there are three impressions, upper impression, middle impression and lower impression. So, upper impression is for supraspinatus, middle impression is for infraspinatus and the lower most impression is for the pterisminus muscle. So, greater tubercle of the humerus, we can remember a mnemonic S-I-T, S for supraspinatus, I for infraspinatus and T for pterisminus. So, supraspinatus proximal attachment, distal attachment have covered. Now, supply of supraspinatus is suprascapular nerve. This arises from the upper trunk of the brachial plexus. There was one more nerve which was arising from the upper trunk of brachial plexus, which nerve was that nerve to subclavius muscle. Then, actions of supraspinatus muscle is it initiates the abduction. 0 to 15 degrees of abduction is done by supraspinatus muscle. Then, infraspinatus muscle, it arises from the infraspinus posa. Muscle goes laterally and to get attached on to the greater tubercle of the humerus, the middle impression. Then, now supply of infraspinatus, it is again the same, that is suprascapular nerve. Suprascapular nerve supplies supraspinatus as well as infraspinatus. The cause of suprascapular nerve is such that it comes from here, near the suprascapular notch. It will supply supraspinatus and then it will come here downwards. This region is referred to as the spinoglenoid notch. From the spinoglenoid notch, the nerve comes downwards and then it will supply the infraspinatus muscle as well. That is how we can remember suprascapular nerve is for both muscles, supraspinatus as well as infraspinatus. Then, action of infraspinatus muscle, since the muscle is going like this and getting attached on to the greater tubercle of the humerus, when this muscle contracts, it will lead to the lateral rotation of the shoulder joint. Let us cover the terris minor and terris major muscles. Terris minor and terris major, these both muscles, they arise from the lateral border of the scapula. The upper two-thirds of the lateral border is terris minor and the lower one-third of the lateral border is terris major. Here, we can see a small gap near the origin of the terris minor. This gap is due to the circumflexed scapular artery which mines around the lateral border of the scapula. Terris minor, this little attachment is over the greater tubercle of the humerus, the lower most impression. Terris major, it goes on the anterior aspect to get attached on to the medial lip of the bicepital groove. Bicepital groove, as you all know, the lateral lip gives attachment to the factorialis major, the medial lip gives attachment to the terris major and the floor gives attachment to the latissimus dorsi muscle. This was about the attachments. Then, nerve supply of terris minor, I have covered in the deltoid muscle, axillary nerve also supplies one more muscle that is terris minor. And nerve supply of terris major is lower subscapular nerve, lower subscapular. Upper and lower subscapular nerve, both nerves were supplying the subscapularis muscle, but the lower subscapular nerve also supplies terris major muscle. Then, action of terris minor will be similar to infraspinitis, lateral rotation of the shoulder joint. Then, terris major muscle, since it is going on the anterior aspect, when it contracts, it will lead to medial rotation of the shoulder joint. Medial rotation is terris major, lateral rotation is terris minor. This was about these four muscles. Here, we can see book image, this muscle is supraspinitis, this muscle is infraspinitis, this muscle is terris minor, and this muscle which is cut, this is terris major muscle. Now, let us look at some dissected images of these muscles. So, here we can see the posterior aspect of the scapula with the muscles. This muscle is supraspinitis muscle, going laterally, getting attached here near the greater tubercle of the humerus. This is the spine of the scapula. Below the spine of the scapula, this muscle is infraspinitis. And this muscle which we can see here, this is terris minor. Terris major muscle is not shown here. It is seen in this image. This muscle is terris major. And this muscle which we can see, this is actually the long head of the triceps brachy muscle. This is long head of triceps. So, now, let us summarize what we have covered in this session. We started with the deltoid muscle. The proximal attachment of deltoid, the anterior fibers of deltoid, it arises from the anterior border of the lateral one-thirds of the glavicle. The middle fibers of the deltoid arises from the lateral margin of the acromion. The posterior fibers of the deltoid, it arises from the lower lip of the spine of the scapula. Distal attachment of deltoid is on the anterolateral surface of the humerus. There is a rough elevation which is referred to as deltoid tuberosity. Distal attachment is on the deltoid tuberosity. Now, supplied by the axillary nerve, the root value is C5, C6, action. Deltoid is the chief abductor of the shoulder joint, 15 to 90 degrees of abduction. And anterior fibers of deltoid are responsible for flexion and medial rotation of the shoulder. And posterior fibers of deltoid are responsible for extension and lateral rotation of the shoulder joint. Then, sub scapula is supraspinitis, infraspinitis, and terris minus. These four muscles are included in rotator cuff of the shoulder, also referred to as musculotendinous cuff of the shoulder. Sub scapula is arising from the anterior aspect of the scapula from the sub scapula rosa. And these three muscles, they arise from the posterior aspect of the scapula. Supraspinitis arises from the supraspinus posa. Infraspinitis arises from the intraspinus posa. And terris minor, it arises from the lateral border of the scapula. The upper two-thirds of the lateral border is a terris minor. And the lower one-thirds of the lateral border is terris major muscles. Sub scapularis muscle, distal attachment is on the lesser tubercle of the humerus. Whereas the supraspinitis, infraspinitis, and terris minor, these three muscles are attached on to the greater tubercle of the humerus. And terris major is attached, distal attachment is on the medial lip of the bicepital groove. Then, actions of supraspinitis, supraspinitis is responsible for initiation of abduction. The 0 to 15 degrees of abduction is by supraspinitis. Infraspinitis and terris minor, they are responsible for lateral rotation of the shoulder joint. And terris major is responsible for medial rotation of the shoulder joint. So, these six muscles, they have covered in this session. So, if you all have any doubts, then you all can ask in the comments section below. Thank you.