 This is one of the most important topic to be studied in upper links, I am covering this topic. So, I will be covering this topic under following headings, we will see what is the definition of break yield plexus, what are the components of break yield plexus, and various branches of break yield plexus, then the two important applied anatomy related to it, Erb s paralysis and Plum K s paralysis. And lastly I will cover some multiple choice questions related to this topic, okay. So, let us begin with the definition, what is break yield plexus? Break yield plexus is the plexus of the nerve formed by the anterior also called as the ventral rami of lower four cervical nerve and the first thoracic spinal nerve, okay. So, C5, C6, C7, C8 and T1, they form the break yield plexus. Remember only, ventral rami they form the plexus. This is the cross section of the spinal cord, supposing this is the dorsal root, this is the ventral root, they unite to form the spinal nerve, which divides into a dorsal ramus and a ventral ramus, okay. The ventral ramus give rise to the break yield plexus. Now, let us cover the various components of the break yield plexus. So, there are four major components, they can be remembered by a mnemonic R, T, D, C, okay. R stands for the roots, T stands for trunk, D stands for the division and C stands for the cords of the break yield plexus and cords further give branches, okay. So, these are the various components of the break yield plexus. If we see roots and the trunks, they are located above the clavicle. Supposing the clavicle bone is here, the roots and the trunks are above the clavicle, and divisions are behind the clavicle and cords are below the clavicle. This is one anatomical landmark which you can remember to identify the various location of the components of the break yield plexus, okay. So, if you see the break yield plexus, it looks very complicated, but we will try to simplify it and easily remember all the components of break yield plexus, okay. So, let us try to draw a simplified line diagram to understand the various components of break yield plexus. So, here I have listed down the five final segments which give rise to the break yield plexus, C5, C6, C7, C8 and T1, okay. So, these are the five roots. At times there may be contributions from C4 as well. In that condition, the break yield plexus is referred to as prefixed break yield plexus, and when there is contribution from C2, the break yield plexus is referred to as post-sixth break yield plexus, okay. But in general, these are the five components. So, C5 and C6 roots unite to form the upper trunk of the break yield plexus, C7 continues as the middle trunk of the break yield plexus, C8 and T1, they unite to form the lower trunk of the break yield plexus, okay. So, this is the roots and these are the trunks. Remember the formula RTDC, RT we have covered, then it will lead to D and C, okay. So, what are D? D refers to the division. The trunk divides into divisions. Upper trunk will divide into an anterior division and posterior division. Middle trunk will divide into anterior division and posterior division. Really lower trunk will divide into anterior division and posterior division, okay. These are the various divisions of the break yield plexus. Then divisions lead to the cords of the break yield plexus. So, remember the cords of the break yield plexus. Let's start with the posterior cord. Posterior cord is formed by the union of the posterior division of all the three components of break yield plexus. Posterior division of upper trunk, posterior division of middle trunk and posterior division of lower trunk. If we unite these three, it will lead to the formation of the posterior cord of the break yield plexus, okay. Anterior division of the upper trunk and anterior division of the middle trunk, they unite to form the lateral cord of the break yield plexus, okay. So, there is only one division which is remaining. That is the anterior division of the lower trunk. That will continue as the medial cord of the break yield plexus, okay. So, these are the three major cords of the break yield plexus. And they are named lateral, posterior and medial according to the, according to their relation with the axillary artery. Supposing here is the second part of the axillary artery. The cord lateral to the axillary artery is lateral cord. The posterior to the axillary artery is posterior cord. The cord medial to the axillary artery is medial cord, okay. This relation is specific for the second part of the axillary artery. Now, let's cover the branches of the break yield plexus. First, we'll start with the branches from the roots. From the roots, if you see, C5, C6 and C7. They unite to form a nerve which is referred to as nerve to serratus anterior. Also referred to as long thoracic nerve. Also referred to as nerve of belt which supplies the serratus anterior muscle. There is one nerve arising directly from C5 that is referred to as dorsal scapular nerve, okay. Also referred to as nerve to rhomboids. Then from the upper trunk of the break yield plexus, there are two nerves. One is suprascapular nerve and other is nerve to subclavius, okay. This region is referred to as herbs point. Because there are six nerves which are meeting here. The C5 and C6 final segments, then these two nerves. Then the anterior and the posterior divisions of the upper trunk, okay. This region is referred to as herbs point. In herbs paralysis, injury occurs in this region. And there are no branches from the divisions, okay. This we should remember. There are branches from the roots. There are branches from the trunks. There are branches from the cords. There are no branches from the divisions, okay. Branches from the cords we'll be covering now. Branches from the lateral cord can be remembered by a mnemonic L, M, L, okay. Where L stands for the lateral pectoral nerve. M stands for the musculoskeletal nerve. And again L stands for the lateral root of the median nerve, okay. Then branches from the medial cord are remembered by mnemonic M4U, okay. Four times M and a U. At 2M, we can remember by comparing with these two L. There is lateral pectoral nerve here. So here there is medial pectoral nerve. There is lateral root of the median nerve here. So here there is medial root of the median nerve, okay. And there are two cutaneous branches. One to the arm and one to the forearm, okay. So the name is medial cutaneous nerve of the arm and medial cutaneous nerve of the forearm. And U stands for the ulnar nerve, okay. Then coming to the branches from the posterior cord of the brachial plexus. Mnemonic for this is ulnar, okay. Remember only the mnemonic is ulnar. Actual nerve, ulnar nerve arises from the medial cord, okay. Here the U stands for upper subscapular nerve. L stands for the lower subscapular nerve. N stands for the nerve to latissimus dorsi. A stands for auxiliary nerve. And R stands for the radial nerve, okay. So these are the various branches from the cords of the brachial plexus. Now let's cover applied anatomy related to it. There's an applied anatomy which is referred to as herbs paralysis. As you all know, herbs point is the region of the upper trunk of the brachial plexus where six nerves meet. So there is injury in that region that it is referred to as herbs paralysis. How is the mechanism of injury? Excessive increase in the angle between the head and the shoulder leads to herbs paralysis, okay. Nerve roots involved are C5 and C6. The typical deformity of the limb is this. There is adduction of the arm, medial rotation of the arm, extension of the elbow and pronation of the forearm. We'll try to understand the anatomical basis of this position. Adduction of the arm is due to the paralysis of the deltoid muscle. Deltoid muscle is supplied by axillary nerve. Root value is C5 and C6, okay. Since deltoid is the abductor of the arm, it is paralyzed. Arm will go in adduction. And there is medial rotation of the arm because the lateral rotators are paralyzed. The in class binators, stairs, minor, okay. Then extension of the elbow. The biceps, brachialis, brachialis, they cause flexion of the elbow. If they are paralyzed, it will lead to extension of the elbow. Then pronation of the forearm. Why is it so? Because the biceps brachia is also a supinator of the forearm. If it is paralyzed, it will lead to pronation of the forearm. Okay. And this deformity is referred to as Polisman's tip hand. Also referred to as Porter's tip hand. Also referred to as Vader's tip hand. Okay. These are the various things which we should be knowing about. Herbs, paralysis. Now let's cover one more applied anatomy related to the brachial plexus. That is clump case paralysis. Clump case paralysis is caused due to hyper abduction of the arm. For example, if falling from a tree, if someone catches an object, it leads to hyper abduction of the arm. In that condition, the lower trunk of the brachial plexus is injured. The root value of lower trunk is C8 and T1. Okay. And this is the important root value for ulnar nerve. Ulnar nerve has root value of C7, C8 and T1. Majorly it is C8 and T1. So the structure supplied by the ulnar nerve will be affected in clump case paralysis. There is a clinical condition called as claw hand, in which there is hyper extension at the metacarpopalangell joint and flexion at the interpalangell joint. This occurs due to the paralysis of the lumbaricals and introsciitis which are supplied by the ulnar nerve. Okay. And there is loss of sensation along the medial border of the forearm which is supplied by the T1's final segment. And there is also a condition which is called as horner syndrome because the T1 sympathetic fibers are affected. It leads to horner syndrome. It manifests as tosses, meiosis and hydroces. Okay. All these are the features of horner syndrome due to the sympathetic fibers of T1 getting affected. Now let's cover some multiple choice questions pertaining to this topic. So this is the question which of the following nerve carries fibers from all the roots of the brachial plexus. All the roots means C5 to T1 which nerve has components from all the roots of the brachial plexus. The other nerve has root values C5 and C6. Ulnar nerve has root values C7, C8 and T1. For record or cell nerve, it is also called as nerve to latissimus dorsi. Root value is C6, C7 and C8. So this nerve which is remaining, median nerve, what is the root value of median nerve? Median nerve it is actually formed by the union of lateral root of the median nerve and medial root of the median nerve. For lateral root of median nerve, root value is C5, C6 and C7. For medial root of the median nerve, root value is C8 and T1. That's how the entire components of the brachial plexus are taking part in the formation of median nerve. Now let's cover an image-based question pertaining to this topic. First, orient yourself towards this image. This is the right-sided axilla. This is the lateral aspect. This is the superior aspect. This is the region of brachial plexus. So a nerve has been pointed out and it has to be identified. Which nerve is this? So to identify this nerve, we can see this nerve is going towards a muscle and it is piercing that muscle. This muscle is coracobrachialis. This muscle is coracobrachialis. Which nerve pierces the coracobrachialis muscle? That's the musculosquitaneous nerve. So that's how we can identify this nerve. In practical examinations, whenever any component of brachial plexus is asked to identify, always we should start with the musculosquitaneous nerve. One of the easiest nerve to identify, because we can see it will be piercing the muscle that is coracobrachialis. And there is something called as m-pattern of the brachial plexus, which we should be knowing. Now what is the m-pattern? This is the musculosquitaneous nerve. This is the ulnar nerve. I am drawing an m here like this. So in this one limb of the m is formed by the musculosquitaneous nerve. Other limb of the m is formed by the ulnar nerve. And the intermediate v-shaped part is formed by the two roots of the median nerve. The lateral root of median nerve is the medial root of the median nerve. Once we have identified the musculosquitaneous nerve, we can trace it backwards and we will reach the lateral cord of the brachial plexus. From the lateral cord we all know there is a lateral root of the median nerve. And it is united by the medial root of the median nerve. That's how we can reach the medial cord of the brachial plexus. And one of the most prominent brands from the medial cord of the brachial plexus is this. That's the ulnar nerve. So that's how by this m pattern we can identify all the major branches of the brachial plexus. For radial nerve, it will be posterior to the axillary artery and it is the thickest of all the nerves from the brachial plexus. So let's summarize what we have covered in this session. We started off with the definition of the brachial plexus. Brachial plexus is ventral primary rami of C5, C6, C7, C8 and T1. We supply the upper limb. Then these are the various components. We can remember by the mnemonic RT, DC. Cords further give rise to branches. We learnt about the branches from the roots, branches from the trunks. Divisions doesn't have any branch. Then there are branches from the cords. Branches from the cords can be remembered by mnemonic. Branches from the lateral cord can be remembered by LML. Branches from the medial cord can be remembered by this mnemonic M4U. Branches from the posterior cord are remembered by this mnemonic ulnar. Then in applied anatomy, we learnt about herbs paralysis and plumb case paralysis. In herbs paralysis, the injuries in the upper trunk of the brachial plexus, nerve roots involved are C5 and C6. In plumb case paralysis, injuries in the lower trunk of the brachial plexus, the nerve roots involved are C8 and T1. So, this was all about this particular session. If you all have any doubts, then you all can ask in the comments section below. Thank you.