 Good day everybody. Dr. Sanjay Sanyal, Professor Department Chair. This is the spine cadaver, right side of the neck and the right side of the axilla. I'm standing on the right side, camera person is on the right side. This is going to be a demonstration of the brachial plexus right from the neck to the axilla. So as we know the brachial plexus is formed from five components, roots, trunks, division, cords and branches. C5, C6 root, they unite to form the upper trunk. C7 root continues as the middle trunk and C8, C1 root forms the lower trunk. Upper, middle and lower trunk. And we can see that these three trunks, they are emerging between this muscle. This is the scalinus anterior muscle and this muscle. This is the scalinus medius muscle. Both of these muscles are attached to the first rib which is located here. So this is the scalin triangle and emerging through the scalin triangle we have the upper trunk, middle trunk and the lower trunk. We cannot see the roots because they are further medially right next to the vertebral column. Also passing through the scalin triangle will be the subclavian artery which we have cut and we have retracted to one side just to show the brachial plexus in more detail. After the trunks we have divisions and we can see that the upper trunk is dividing into an anterior division and a posterior division. The middle trunk is also supposed to divide but here we can see that it is sharing the fibers but the division is not clearly visible. And the lower trunk, the division is not clearly visible but it is sharing their fibers. Then we have cords, anterior division of both unite to form the lateral cord of the brachial plexus and this is the lateral cord. The anterior division of the lower trunk continues as the medial cord and this is the medial cord of the brachial plexus. And all the posterior divisions unite to form the posterior cord and this is the posterior cord of the brachial plexus. And then we have the terminal branches. Having mentioned that, now let's come back again. The trunks can get compressed in the scalin triangle and that is called scalin syndrome and it can also compress the subclavian artery. And we can see that since the scalinus anterior muscle and the scalinus medius muscle are inserted onto the first rib, if there is a cervical rib, then the lower cord is also likely to be compressed. So this is the scalin syndrome or the thoracic inlet syndrome or the costoclavicular syndrome. We can see that this point where we have the upper trunk dividing into anterior and posterior division, we can see this branch coming out. This is the supra scapular nerve and also emerging from this will be the nerve to subclavius. Which supplies this muscle, this is the subclavius muscle and as it supplies in small percentage of patients, it can also give rise to an accessory phrenic nerve, which can cross in front of the subclavian vein and can unite with the vein phrenic nerve here. And in which case it can entrap the subclavian vein. So therefore this point exactly where my instrument is pointing, this is referred to as the herbs point. And this is a site of lesion and that is known as herb deusion paralysis or upper brachial pexus lesion. Because six things are happening here, the upper trunk is dividing into anterior and posterior supra scapular nerve is coming out. The nerve to subclavius is coming out. This is the herbs point. Now let's continue further. Let's pick up the lateral cord. This branch coming out from the lateral cord. This is the lateral pectoral nerve and we can see it is giving a communication which is going to the medial pectoral nerve in front of the brachial plexus. The lateral pectoral nerve supplies the pectoralis major. Then we can see this nerve coming out from the lateral cord. This is the musculocutaneous nerve which supplies the muscles of the arm, the anterior aspect. And then we have this structure coming out. This is the lateral root of the median nerve. So that brings me to the medial cord. As I said, this is the medial cord. The medial cord is giving this branch here. This is the medial root of the median nerve and the two are uniting to form the median nerve. Ideally, this should have united here at this point, much higher up. Here the union is occurring much lower down. So therefore the median nerve is formed by the lateral root of the median nerve coming from the lateral cord and the medial root of the median nerve coming from the medial cord. What are the other branches coming from the medial cord? We can see this branch coming out. And if we trace it further up, we can see it is starting from here. This is cutaneous nerve of the arm and the cutaneous nerve of the forearm. Additionally, we can see this branch coming out from the medial cord. It is rather low down, so we have to see it very carefully. This is the branch. This is the medial pectoral nerve. And we can see that the medial pectoral nerve is receiving a communication from the lateral pectoral nerve, which I mentioned just a little while back. Medial pectoral nerve supplies the pectoralis minor and then it pierces through the pectoralis minor and supplies the pectoralis major. Again, to come back to the medial cord, we can see after it is given off this branch and after it is given off the medial root of the median nerve, the rest of the medial cord is continuing here. This is the ulnar nerve. This runs from the medial side of the arm and it goes behind the medial intermuscular septum and behind the medial epicondyle. So these are the structures which are coming out from the medial cord. Now let's come to the posterior cord, the brachial plexus. This is the posterior cord, the brachial plexus. And let's take a look at all the branches which are coming out from the posterior cord. We can see this branch. This is the upper subscapular nerve, which supplies the subscapularis muscle and this is the subscapularis muscle. Then we have this branch coming out and we can see it's moving here. This is the thoracodorsal nerve. And we can see it is running now and it's supplying this big muscle. This is the latsomus dorsi. And it is accompanied by the thoracodorsal vessels here, which is coming from the third part of the axillary artery. If the nerve to latsomus dorsi, that is the thoracodorsal nerve is injured, then there is the latsomus dorsi paralysis. And the patient will not be able to climb. It is referred to as the climbing muscle and the person will not be able to use his crutch. Then we can see this nerve. This is the lower subscapular nerve and this supplies the t-rease major. And we can see this is the t-rease major and it also supplies the subscapularis. So therefore the subscapularis receives nerve from the upper subscapular and lower subscapular. Lower subscapular supplies t-rease major. To continue with the posterior cord, we can see this nerve disappearing inside the quadrangular space. This is the axillary nerve. And the axillary nerve as it goes through the quadrangular space, it is accompanied by this artery here. This is the posterior circumflex humeral artery. They go through the quadrangular space and this nerve can be injured in inferior dislocation of the shoulder joint, in which case there will be deltoid paralysis. And the rest of the posterior cord is then continuing. This is the radial nerve. And just to complete the picture, I'll draw your attention to this nerve here. This is the long thoracic nerve of Bell and we can see it is accompanied by this vessel here. This is the lateral thoracic artery which comes from the second part of the axillary artery. This runs on the surface of the chest. It supplies the sedentus anterior muscle. And we can see the origin of this nerve here. The middle portion has been removed. This is the origin. This arises from the roots of C567. And if this nerve is injured, then there will be paralysis of the sedentus anterior muscle and it will lead to winging of the scapula. This is the clinical picture to show winging of the right scapula when the patient is asked to press against a wall. So these are all the branches of the brachial plexus that we can see here right from the neck through the cervical axillary canal to the axilla and the terminal branches. And before I conclude, I need to mention one point. The branches of the brachial plexus can be divided into two categories. One set of branches are those which arise from the roots, trunks. There are no branches from the division and from the proximal part of the cords. Those are called collateral branches. They are actually part of the brachial plexus. While there are other branches which are called the terminal branches which arise from the end of the brachial plexus and they supply the arm, upper limb. They are not truly part of the brachial plexus. And the terminal branches are MARMU. M musculocutaneous, A axillary, R radial, M median and U ulnar. So therefore these are the terminal branches of the brachial plexus and they are not considered strictly speaking as part of the brachial plexus. So this is what I wanted to show you in the brachial plexus all the way from the neck to the axilla and to the arm with their respective clinical correlations. Thank you very much for watching. Dr. Sanjay Sanyal Sanyal, Mr. Kendal Kumbabaj, the camera person. If you have any questions or comments, please put them in the comment section below. Have a nice day.