Musculocutaneous Nerve

00:01 In this lecture, we're going to look at a series of nerves in the upper limb and what happens if these are damaged. So, nerve lesions of the upper limb.

00:10 Let's start off by looking at the musculocutaneous nerve.

00:14 And first of all, let's remind ourselves of the course of this nerve.

00:19 So, the musculocutaneous nerve is the direct continuation of the lateral cord of the brachial plexus and it goes on to supply coracobrachialis.

00:28 Here, we've got the musculocutaneous nerve then passing through coracobrachialis, this supply biceps brachii and the brachialis muscle.

00:37 It then, passes all the way down and you can see the musculocutaneous nerve innervating coracobrachialis, biceps brachii and brachialis.

00:45 You can also see the biceps brachii tendon there.

00:48 As the musculocutaneous nerve passes down through the arm, it also gives rise to the lateral cutaneous nerve of the forearm.

00:55 So, this is the nerve that supplies the skin and that's important to recognize that these nerve contain motor fibers to the muscles but also take sensory innervation back to the spinal cord from the surface of the skin.

01:09 And the musculocutaneous nerve gives off this branch.

01:11 The lateral cutaneous nerve of the forearm which supplies the skin on that lateral aspect.

01:17 We could see it depicted here on this model.

01:20 So, this area of skin is supplied by the musculocutaneous nerve.

01:24 If we were to have damage to the musculocutaneous nerve and this could happen to a number of reasons, maybe some penetrating traumatic injury within the axilla, then, obviously, all of the muscles that are supplied by that nerve distal to where that injury occurs are going to no longer receive their motor supply.

01:43 So, we have paralysis therefore of coracobrachialis, biceps, and brachialis muscles.

01:50 This means we're going to have weakened flexion of the elbow and weakened supination of the forearm.

01:56 So, if the muscles that perform these movements are no longer innervated, then, those movements are going to be weakened.

02:03 We'll also have a loss of sensation from that lateral part of the forearm because nerve fibers now running back with that sensation to the spinal cord will be interrupted via this trauma.

02:15 So, this is a nice, relatively straightforward example of what we mean by these nerve lesions.

02:21 They're going to impact the muscle supply distal to where that injury occurs and all sensation that is distal to that injury will not be able to return to the spinal cord.

02:32 Everything that is occurring before proximal to this lesion will still work as planned because obviously, there's no interruption to the nerve fibers.

02:42 So, the musculocutaneous nerve is a nice, interesting first look at these nerve lesions.