 Good day everybody. Dr. Sanjeev Sanyal, Professor Department Chair. So this is going to be a demonstration of certain spaces and the neurovascular structures therein. This is a prone cadaver. This is the right side of the cadaver. Just to bring up to speed, this muscle, this is the latsomal dorsi. This is the T.D.'s major. This is the T.D.'s minor. This is the infraspinatus and this is the supraspinatus. This is the trapezius, which we have lifted up and this muscle that we see here, this is the deltoid. To continue, this is the long head of the triceps. This is the lateral head of the triceps, which we have cut here and deep inside we can see this muscle here. This is the medial head of the triceps. So with this background, now let's come to the first space. We can see a quadrangular space, bounded, inferiorly by the T.D.'s major, superiorly by the T.D.'s minor, medially by the long head of the triceps and laterally by the surgical neck of humerus. So this space is the quadrangular space and passing through the quadrangular space, we can see this structure, which I have lifted up here. This is the axillary nerve and accompanying this axillary nerve, we can see a blood vessel. This is the posterior circumflix, humeral artery and vein, which comes out from the axillary artery. The posterior circumflix, humeral artery and vein, it comes out from the third part of the axillary artery. As it comes out, the axillary nerve, it gives a branch and we can see that branch here. It gives a branch to the T.D.'s minor and the rest of the axillary nerve then continues through the quadrangular space and we can see one branch here and we can see another branch here and they enter the inner surface of the deltoid and I have put my finger here to lift up the whole thing. And it supplies the deltoid muscle and after that it pierces through the deltoid and supplies the skin in this region. So this is the content of the quadrangular space. In this connection, we have some important clinical correlations. If there's a fracture of the surgical neck of humerus where my finger is located. This is the next rave, the shoulder to show fracture of the surgical neck of the right humerus. Or if there's an inferior dislocation of the head of the humerus, which is located just above the quadrangular space, then it can impinge on the axillary nerve and can produce an injury to the axillary nerve. And that will lead to paralysis of the deltoid. The person will not be able to abduct his shoulder from 15 degrees upwards. There will be atrophy and basting of the deltoid. The acromion process will become prominent. The paralysis of the T.D.'s minor is not clinically significant. So that is one structure that we can see here. Now let's move a little medially. We can see a triangular space bounded below by the T.D.'s major, above by the T.D.'s minor, laterally by the long head of the triceps. This triangular space is called the triangular space itself. And if we look very closely, we can see an artery going through the triangular space. This is the circumflex scapular artery. The circumflex scapular artery enters into the scapula between the attachments of the T.D.'s major and the T.D.'s minor. And it participates in the scapular anastomosis. This scapular anastomosis is a communication between the branches of the third part of the axillary artery and the branches of the first part of the subclavian artery. And it provides an important collateral circulation in occlusion of the subclavian artery. And as you grant to show occlusion of the subclavian and the axillary artery and prominence of the right scapular anastomosis. To continue with the same, we can see this artery coming from deep inside. This is the last branch of the third part of the axillary artery called the subcapular artery. And we can see that it is giving this branch here. This is the circumflex scapular and the rest of it we can see is continuing downwards and I've lifted it up here. This is the thoracodorsal artery. And if we were to trace the thoracodorsal artery on this side and I've retracted the T.D.'s major and the latsomers dorsi and we can see the thoracodorsal artery here with the vein entering into the latsomers dorsi. So this is the full course of the subcapular artery dividing into thoracodorsal and the circumflex scapular going through the triangular space. Now let's come a little laterally and further lower down. We can see a triangular interval. It's called interval because the vessels are visible through it but they are not passing through the interval. First let's take a look at the boundary of the triangular interval. In the triangular interval we have come below the T.D.'s major. So this is the T.D.'s major. Medially it is bounded by the long end of the triceps and laterally it is bounded by the lateral end of the triceps which we have cut and we can see these neurovexical structures passing through. This is the radial nerve and accompanying it is this vessel here. This is the profunda brachii artery and the profunda brachii vein which comes out from the brachial artery. The radial nerve after it is visible through the triangular interval it enters this area here and my finger is located in this region and we have split this. This is the radial groove or the spiral groove on the posterior aspect of the humerus and it is located under the lateral head of the triceps between the lateral head and the medial head. As a matter of fact the lateral head is called lateral head because it is lateral to the radial nerve and the medial head is called medial head because it is medial to the radial nerve. This is the radial of the spiral groove. In the triangular interval if there is hypertrophy of any of these muscles it can compress the radial nerve but even more important than that if there is a fracture of the mid shaft of the humerus then it can injure the radial nerve and in which case it will produce paralysis of the extensor muscles of the arm. This is the next ray of the left arm of the patient showing fracture of the shaft of the humerus. What about the triceps itself? We can see that the branch to the medial head of the triceps comes out from high up and this is the branch to the medial head of the triceps and we can see that here. So therefore the medial head of the triceps receives a branch before the radial nerve enters the triangular interval or the radial groove. Even the long head receives a branch before while in the triangular interval and in the radial groove the lateral head receives branches. So therefore if there is a fracture of the mid shaft of the humerus most of the triceps will be spared. Only the lateral head will be paralyzed and lateral head as we know is responsible for powerful extension. So therefore extension of the elbow will not be a serious disability but wrist drop will be a serious disability. And to continue further as it goes down it continues and it comes to the elbow in front of the lateral epicondyle and thereafter we can see it only in anterior view. Just a few quick words about this profunda brachii artery. We can see it here. We can see that it is giving communications with anastomosis with the posterior circumflex humeral artery. The profunda brachii comes down. It is a big artery. It's a deep artery of the arm and it comes to the back of the arm and here it finishes by giving a radial and a middle collateral artery. This radial and the middle collateral artery in conjunction with the superior and inferior ulnar collateral artery participates in what is known as elbow anastomosis. This is reinforced by four arteries from below the anterior and posterior ulnar recurrent, a radial recurrent and interocious recurrent. So therefore four arteries from above and four arteries from below they form an elbow anastomosis and they provide collateral circulation in case of radial artery occlusion and blood supply to the arm. So these are the three spaces that we saw. The quadrangular space, triangular space, triangular interval with their respective clinical correlations. Now let's come to the medial side. We can see this septum here. This is the medial intramuscular septum which is attached to the medial supra-condyler ridge of the humerus and running behind the medial intramuscular septum we can see this nerve here and if you were to trace it here we can find that it is disappeared here. That means above this it is in front of the medial intramuscular septum and below this it is behind the medial intramuscular septum. This runs on the medial side of the arm and we can see it is disappearing just behind the medial epicondyle. This is the medial epicondyle. This location where my instrument is located this is called the cubital tunnel. How is this cubital tunnel formed? It is formed by the olecranon process the medial epicondyle a bridge of aponeurosis which is formed by the aponeurotic expansion of the flexor carpi ulnaris which bridges over between these two and it fuses with anti-brachal fascia and it fuses with the subcutaneous part of the ulnar so this forms a tunnel and that is referred to as the cubital tunnel and we have split that cubital tunnel here and we can see one margin of the split here and we can see the other margin here and we can see running through the cubital tunnel is the ulnar nerve. This ulnar nerve can be injured in fracture of the medial epicondyle but more commonly than that it can also get entrapped in this cubital tunnel and that is referred to as cubital tunnel syndrome injury to the ulnar nerve will produce numbness, tingling, peristhesia on the medial side of the hand and the forearm and it will also produce what is known as a radial claw hand and accompanying this ulnar nerve we have seen this is the superior ulnar collateral vessel which I have already mentioned participates in the elbow anastomosis and just to complete the story this vessels and nerve that we see here they are not related to this discussion this is the basalic vein and this is the medial cutaneous nerve of the forearm which is present on the medial side of the arm and the forearm so these are the structures which I wanted to show you these neurovascular structures with their respective clinical correlations thank you very much for watching Dr. Sanjay Sanyal signing out David O's the camera person if you have any questions or comments please put them in the comment section below have a nice day