Today we will discuss the nerves supply the upper limb, and our focus will be principally upon the nerves that supply the musculature of the limb. So, our objectives here are to name the nerves that contribute to the brachial plexus. To describe the significance of the chords of the brachial plexus. Describe the contribution of the cords to the terminal nerves, and name the target compartments of the nerves. To begin with what you see often in anatomy, the term plexus. A plexus is and in the simplest sense where numerous nerves come together intermingle and they redistribute to reach their targets. The plexus that supplies the upper extremity is called the branchial plexus. The branchial plexus is composed of nerves from the mid and lower cervical region to 1. So from C5 to T1, these nerves leave the spinal column intermingle and then distribute to their targets. We see here the nerves leaving the spinal column and passing posture to the clavicle and connecting and distributing as they go. We removed the clavicle here to show a little more detail of the organization. An organizing principle for understanding the branchial plexus involves having some sense of what are called the chords of the branchial plexus. We can see here that the nerves intermingle here to form a lateral cord and another nerves intermingle to form a posterior cord, and another set of nerves intermingle to form a medial cord. These cords are named because of their relationship to the axillary artery which we talked about earlier. So the lateral cord, lateral to the axillary artery, the medial cord, middle to the axillary artery, and the posterior cord posterior to the axilliary artery. We talked first about the musculocutaneous nerve, which arises from C5 and C6. And it's from the lateral cord of the branchial plexus, and the muscular targeted of the nerve are the biceps and break the Alice in the anterior on. So, these are the muscles responsible for flexion of the elbow innovated by the by the branchial plexus. There's also a minor muscle branchial plexus, which is innovated as well. And this cross section through the mid arm shows these what we call the anterior compartment of the arm supplied by the biceps and branchial plexus. We'll see soon the innovation of the posterior compartment of the artery. The axillary nerve also arises from C5 and C6. It actually emanates finally from the posterior cord and it supplies the deltoid muscle that you recall the large muscle that abducts the shoulder as well as the terrys minor, which is one of the rotator cuff muscles. A lateral rotator of the shoulder. And this image again shows a cross section through the shoulder and shows the deltoid muscle supplied by the axillary nerve wrapping around the shaft of the humerus. The super scapular nerve also rises from C5 and C6. But it arises proximal to the cords of the branchial plexus, which is the same more medially closer to the origin from a part of the brachial plexus called the upper trunk. And it supplies the super spin and. We see this as a posterior view of the scapula, we remind ourselves that we have the spine of the scapula here. The super space arises from the scapula superior to the spine. Any arises from the scapula inferior to the spine. We recall, I expect that the super is an abductor of the shoulder. We see it here passing over right here the head of the humerus to attach to the upper part of the shaft and then slightly more inferior. Early here we see the interest bananas which is one of the rotator cuff muscles and the lateral rotator. The radial nerve has a large contribution from nearly all of the roots of the brachial plexus and it arises from the posterior cord. And here we start to think now about how this nomenclature can help us. The posterior cord supplies both the posterior arm and the posterior forearm. So, we see here the posterior compartment of the arm, and we see the triceps muscle entered innovated by their radial nerve which is one of the main outputs of from the posterior cord. And we see here in the forearm it supplies the digital and again posterior cord posture, posterior arm and posture your forearm all all make sense and go together. We now look at the median nerve and the median nerve arises from the lateral and medial cords and its target is anterior forearm and hand. And we'll see shortly, that's also true of the ulnar nerves. So, for thinking about general sense about the targets of these cords. Both the medial and lateral cord are innovate anterior forearm and hand and the posterior cord which we just talked about, innovates posterior arm and posture your forum. So, the median nerve then has no branches in the arm and it supplies most of the anterior forearms. So, we're thinking about the anterior forearm, we think about the lectures of the wrist and the fletchers of the digits as well as that very important set of muscles. The thinner muscles that control movements of the thumb, and then two of the intrinsic muscles of the hand, the lumberckles. The ulnar nerve arises from the medial cord. It has a small amount of innovation to the anterior forum and it supplies most of the intrinsic muscles of ban the ones not supplied by the median nerve. For again, thinking in general terms about the distribution of nerves, we see that C8 and T1 are responsible for the medial cord. And the ulnar nerve is one of the main outputs of that medial cord and its target is additional extremity principally the hand. So we saw C5 and C6 supplying more medial musculature, and C8 and T1 supply and more distal musculature. So, this image here shows a complicated set of muscles here. We show the posterior forearm which we talked about before supplied by the radial nerve and the anterior forearm. The muscles are supplied mostly by the median nerve except for a small amount of muscle, they're supplied by the ulnar nerve. As we progress to the proximal hand, there's a cross section here. This is the thumb side of the hand. This is a part of the section through the scene are evidence which is supplied by the median nerve. And medially here on the ulnar side of the hand, we see a small amount of muscle supplied by the ulnar. And then as we progress more distally into the palm, we see these are intrinsic muscles of the hand which lie between the metacarpals and almost all of these are supplied by the ulnar nerve. Okay, so let's review some of the main points that we've discussed about nerves and branchial plexus, and terms of a quick quiz again this is on graded low pressure. Let's just kind of re examine some of the principles that we've talked about. So, begin with radio plexus arises from spinal levels from C5 to T1. What do you think? You said true that's good. That's the upper extremity is supplied by segments at that level. Segments below that level would be involved in innovation of the chest and more inferiority the pelvis and lower extremity cords of the branchial plexus. Remember, we talked about cords and their importance in thinking about the way their branchial plexus was organized. Are named for their relationship to the humorous shaft. Think about that for a moment. If she said false, that's good. I hope you remember now that the cordial branchial plexus are named for their relationship to the axillary artery. Another question. The posterior cord supplies the posterior arm and forearms. She said true, that's good. And you might also remember that the posterior cord also gives rise to the axilliary nerve which supplies the the deltoid and the terry's minor at the shoulder joint. Now, which muscles are supplied by the median nerve biceps, triceps, fllexors of the digit, thenar muscles or wrist extensors. Think about that for a moment. Okay so, I hope you'll recall that the biceps is supplied by the musculautaneous nerve. The triceps, which is in the posterior arm is supplied by the radio nerve. The median nerve does supply the flexors of the digits except for a small part of them supplied by the ulnar nerve and it supplies the thenar muscles. These critical muscles in terms of of movements of the thumb. And the wrist extensors which are muscles of the posterior forearm are supplied by the radial nerve. Muscles of the anterior forearm are supplied mostly by which nerve? She said median nerve, that's great. And if we recall a little more detail, you may remember that the ulnar nerve supplies a small number or a small part of the musculature of the anterior forearm. Okay, which muscles are supplied by C5 and C6? Think about that for a moment. She said, all of them are supplied by C5 and C6, that's good. Recall that the biceps is supplied by the musculocutaneous nerve. The deltoid is supplied by the axillary nerve, and superspinatus and infraspinatus are supplied by the superscapular nerves. So, all of these nerves, despite their apparent wide distribution are supplied by the C5 and C6 spinal nerves. Which muscles are supplied by C8 and T1? So, we're now talking about the lower part of the branchial plexus. C5 and C6 might be described as the superior or upper part. Now, we're talking about C8 and T1, the most inferior part of the branchial plexus. So, which muscles are supplied by them? If she said all of them, that's great. Recall that the media nerve supplies the muscles of the thenar eminence flexor pollicis brevis. Abductor pollicis brevis and opponens policies and the interossei muscles, the muscles between the metacarpals. They are supplied by the ulnar nerves. So again, just as we saw in the previous question, segments of spinal nerve can branch to supply various muscles through different nerves. So, the hand then being distal, is supplied mostly by the most inferior parts of branchial plexus. Thank you, we'll see you soon.
