 Okay, so this is going to be a demonstration of some spaces and tunnels with their clinical significance. These are usually described in textbooks, but they're hardly ever shown in the sections. So to bring you up to speed, this is the prone cadaver and this is the right side. We are seeing it from the back. So we have to get the orientation clear. This is the trapezius muscle that we can see here. I'm going to reflect the trapezius. Then only we can see the deeper structures. So I have reflected the trapezius and then we can see the next muscle here. This is the supraspinatus. This is the spine of the scapula. And under that we have the infraspinatus. These were covered by a thick, tough fascia which has been removed. This is the deltoid muscle. This also we have cut and reflected to show the next muscle under the infraspinatus, this muscle. This is the teres minor. So therefore the supraspinatus, infraspinatus, teres minor and the subscapularis, which is deep inside here where my finger is located, they constitute the rotator cuff. They get fused with the shoulder capsule. To continue, this is the teres major. This is the long head of the triceps, taking origin from the intraglinoid tubercle of the scapula and this is the lateral head of the triceps. And this is the surgical neck of the humerus. Just to complete the story, since we have reflected the trapezius, we can see this muscle here. This is the rhomboidus major. This is the rhomboidus minor. And this is the levator scapulae. But we are not going to talk about that at this juncture. So having mentioned these muscles, I'm going to demonstrate the spaces and the triangles and the structures passing through them with the clinical correlations. Let's start with this space here. This is the quadrangular space. The quadrangular space is bounded by the teres minor above the teres major below. Above is also the head of the humerus and in front will be the subscapularis. Medially we have the long head of the triceps and laterally we have the surgical neck of the humerus. So this is the quadrangular space. This quadrangular space gives passage to this structure that we can see here. This is the axillary nerve. We can see the axillary nerve is giving a branch to the teres minor. But the main axillary nerve is deeper down and this is the main axillary nerve. And this main axillary nerve supplies the deltoid muscle from inside. And we can see it's giving multiple branches to the deltoid. And after it has supplied this deltoid muscle, it will pierce through and it will supply the skin on the upper lateral aspect of the arm. Accompanying this axillary nerve, we have these vessels here. This is the posterior circumflex humeral artery and the posterior circumflex humeral vein. So this whole neurovascular structure passes through the quadrangular space. The clinical coordination pertaining to this is in inferior dislocation of the shoulder joint. As I mentioned, the head of the humerus is just above the quadrangular space. Or in fracture of the surgical neck of the humerus, it can injure these structures, especially the axillary nerve. In which case, the paralysis of the deltoid will produce flattening of the shoulder and inability to abduct. This is a very serious disability. So this is the quadrangular space. Now we are going to move a little medially. We will still be between the teres minor and the teres major, but now we are going to move medial to the long head of the triceps. And that is this space here. This is the triangular space. And we can see the triangular space is giving passage to, again, some blood vessels. This is the circumflex scapular artery. The circumflex scapular artery enters into the scapula between the teres major and the teres minor. And it is accompanied by the circumflex scapular veins. The circumflex scapular artery is the smaller terminal division of the sub scapular artery, which comes out from the third part of the axillary artery, the other branch being the thoracodorsal. And it forms a scapular anastomosis. This scapular anastomosis basically is an anastomosis between the branches of the third part of the axillary artery with the first part of the subclavian artery. More specifically, the dorsal scapular artery and the suprascapular artery. Now this, again, is a very useful anastomosis. If there is any subclavian axillary thrombosis, then this anastomosis constitutes a main form of circulation to the upper limb. Likewise, if any surgical intervention has to be done or if the axillary artery has to be ligated, or if there is any injury to the axillary artery and it requires an intervention, then the axillary artery should be ligated above the origin of the subcappular artery so that the subcappular artery can give the circumflex scapular, which will participate in the scapular anastomosis and the circulation to the arm will be maintained. So that is about the clinical significance of the triangular space. Now from the triangular space, we will move below the T.D.'s major and we will be lateral to the long head of the triceps. This triangular space that we see here, this is called the triangular interval. So this is bounded above by the T.D.'s major, medially by the long head of the triceps and laterally by the lateral head of the triceps and again the humerus. So this is the triangular interval. And it is best seen when I reflect the long head of the triceps and now we can see the contents of the triangular interval. We can see the contents here much more clearly. We can see this structure here. This is the radial nerve. The radial nerve supplies the triceps. Before it enters into the radial groove, it supplies the long and the medial head of the triceps and then it enters into the radial groove. And then it runs behind and it supplies the lateral head of the triceps. Accompanying the radial nerve, we have this vein here and we have this artery here. This is the profunda brachii artery. We can see this is the brachial artery and arising from that is the profunda brachii artery and the profunda brachii vein. They also accompany the radial nerve and they run through the triangular interval. Just to bring you up to speed, this was the triangular interval we saw and now we are seeing it from the other side. So here again we have some important clinical correlations. In fracture of the mid shaft of the humerus, the radial nerve can be injured. In which case, it is likely to produce paralysis of the lateral head of the triceps because the long and the medial head of the triceps have already received branches before it enters the radial groove. Another important clinical correlation is sometimes abnormal insertion of these muscles can produce entrapment of these nerves or these vessels, namely the profunda brachii as well as the radial nerve. Likewise, if for any reason we have to ligate the brachial artery, we should do it below its profunda brachiae branch so that the profunda brachii can be given off and it can provide circulation of the arm through the elbow and osmosis. So this is the triangular interval with the neurovascular structures and finally, since we are looking at the structures from the posterior aspect, this is the right time to show yet one more structure. This nerve which I have picked up, this is the ulnar nerve and we can see the ulnar nerve, normally it runs behind the medial intramuscular septum and we have got the medial intramuscular septum so we cannot see it from the front but we can see it clearly from behind. The medial intramuscular septum is attached to the medial supra-condyler line. Ulnar nerve does not give any branches and arm, it just gives a few articular branches to the elbow and we can see those articular branches. The medial ulnar nerve then runs posteriorly and it runs behind the medial epicondyle and this is the medial epicondyle and we can see it is running here and while it is running, it enters into a tunnel and this tunnel, I am going to put my instrument now to show you, this is the tunnel. This is the cubital tunnel. How is this cubital tunnel formed? The cubital tunnel is formed by an apocalyptic expansion from the flexor carpi ulnaris. The flexor carpi ulnaris aponeurotic expansion comes like this and it bridges over the between the medial epicondyle and the posterior aspect of the ulnar and it fuses with the anti-brical fascia and it gets attached to the posterior aspect of the ulnar thus forming a bridge like this and we have cut open part of the bridge to show the cubital tunnel. This ulnar nerve passes through the cubital tunnel and here again we have two clinical correlations. In fracture of the medial epicondyle, the ulnar nerve can be insured and while the ulnar nerve is passing through the cubital tunnel it can get entrapped here and the condition known as cubital tunnel syndrome in which case there will be weakness of the intrinsic muscles of the hand and there may be a claw hand and loss of sensation on the medial side of the palm. So these are the structures that we wanted to show you with the clinical correlations. Thank you very much for watching. Dr. Sanjay Sanyal signing out. If you have any questions or comments please put them in the comment section below. Have a nice day. Mr. Kendal Kampar Batch is the camera person.