5. Major Nerves | Upper Limb Anatomy | Dr. Azam | Medical Maven

Added: 2026-05-15

[00:00:06]Welcome back my dear friends and now let us move towards the next segment and the next most important segment in upper limb topic. So we are now moving towards the discussion of the all the major nerves and the minor nerves which we have seen in the brachal plexus guys. So what I will do here first of all let me tell you the entire planning like how we're going to approach this topic and how we're going to make it easy. Then uh later on I'll tell you like how to discuss all the major nerves in the easiest manner possible. So first of all look at this diagram here guys. We have discussed the entire brachial plexus in detail. You can look on the screen here.

[00:00:41]We have discussed the entire brachial plexus in detail and I hope my all my students are like expert in this one.

[00:00:46]Now there are so many branches that you are able to see in the brachial plexus over here. Now out of that many many branches do one thing from now onwards from today onwards what you have to do is divide all the branches of the breakal places into two categories. One is major branches another one will be the minor branches. Now you might be like what is this major branches and minor branches here remember major branches will be those branches those long long branches which will be going ahead and supplying to the muscles of your arm forearm and hand. So those are the major branches. Minor branches will be supplying to only and only the muscle surrounding the shoulder region here.

[00:01:23]Pectoral region. I mean to say like pectoralis major, pectoralis minor, tus major, tius minor, all those muscles guys. Understanding. So that is the difference between the major nerves and the minor nerves. Fine. Now once you understood the meaning here like what is major, what is minor? Out of all these branches like which are the major branches and which are the minor branches. If you have observed my diagram properly, I have written like five branches in capital letters.

[00:01:49]Everything is like well planned. Okay.

[00:01:51]So five branches I have written here in capital letters and those are the major branches and remaining all are minor branches guys. So let's see here. Number one muscularcutaneous nerve number two the median nerve. Number three axillary nerve number four radial nerve and number five the alna nerve. So these are five branches that we have written here in capital letter those are the major branches and remaining all are minor branches that makes the things easier for you understanding and first of all what we'll do is we'll try to discuss these major branches then we'll go ahead with the minor branches later on okay now now I'll give you one important golden rule guys that makes your life easier to tell the nerve supply to each and every muscle fine what is that golden rule first listen to me then we'll Later on we'll write down together. Now arm, forearm and the hand.

[00:02:44]In the arm, first of all, all the muscles of the arm are divided into two categories or two compartments. Anterior compartment and the posterior compartment.

[00:02:53]In the forearm, the muscles are divided into two compartment. One is the anterior compartment. Another one is the posterior compartment. And in the hand, there are no compartments only simply the muscles of hand. And I have already discussed all these muscles in detail in our previous videos. So that it'll be very much easier for us to discuss this major nerve. Guys, just follow my planning guys. Just follow all the videos in the same sequence. Is it okay?

[00:03:15]I repeat once more here. Arm, anterior compartment and the posterior compartment, forearm, anterior compartment and the posterior compartment. And in the hand, simply the muscles of hand here. Now all the muscles in the anterior compartment of the arm, listen carefully guys. All the muscles in the anterior compartment of the arm will be supplied by muscularcutaneous nerve.

[00:03:36]All the musles in the posterior compartment of the arm will be supplied by radial nerve. Similarly, all the musles in the posterior compartment of forearm also will be supplied by radial nerve only. So radial nerve is the one which will be supplying to the entire posterior compartment. Entire posterior compartment guys. The anterior compartment of the forearm. All these muscles are supplied by two nerves. One is your alna nerve, another one is media nerve. Now the same ala nerve will continue ahead and the same media nerve will be continuing ahead and they are the one which will be supplying to all the muscles of your hand that makes our life simple understanding here. So here it is muscularcutaneous here it is radial and again radial here and here it is and median and then muzzles of hand again it is allar and medium guys. Okay so all these are the major nerves. Now let us just write down make a note of this one. So we are going to first discuss about the major nerves.

[00:04:26]So in total we are dividing all the nerves into major and minor. In total there are five major nerves guys. And these major nerves they'll be supplying to your compartments or the muscles of your arm and the forearm and hand.

[00:04:43]The muscles of your arm, forearm and the hand. Now in the arm all the muscles are actually divided into two compartment.

[00:04:48]One will be the anterior compartment of the arm and another one will be the posterior compartment of the arm. This and as we have discussed just now all the muscle in the anterior compartment of the arm will be supplied by muscularcutaneous nerve.

[00:05:06]Muscularcutaneous nerve guys and the posterior compartment of the arm all the muscles will be supplied by radial nerve. Wow. Next one. In the forearm all the muscles are actually again divided into two compartment. One will be the anterior compartment and another one will be the posterior compartment. Rest and then all the muscles in the posterior compartment are supplied by which nerve only? They are supplied by radial nerve. Fine. And the muscles in anterior compartment of the forearm will be supplied by two nerves that is your alnar nerve and median nerve.

[00:05:43][snorts] Alna nerve and the media nerve.

[00:05:44]And as I told you in the hand no compartments at all guys. Just you got to remember that all the muscles in the hand will be again supplied by your alna nerve and the median nerve. That's all easy. So such an small small table here but it makes a clearcut idea in your mind. Okay. So if tomorrow someone ask you the question biceps muzzle will be supplied by muscular cutaneous nerve.

[00:06:07]Similarly triceps will be supplied by radial nerve. So in this manner like you know flexars should be supplied by nar and median and the extensors should be supplied by radial nerve. It makes sense now. Now if you're observing properly here totally we are having like how many major nerves guys totally we are having five major nerves but out of them we have just written only four of them. One more which is left out here is your auxiliary nerve.

[00:06:30]Now remember axillary nerve will be supplying to only and only two muscles guys [snorts] and just remember that two muscles forever. Number one will be your deltoid muscle.

[00:06:43]Deltoid muscle and number two will be the ter muscle. But the important thing is whether it is ter minor or major. I want you all to concentrate there. Most of the students will be making a mistake there only. So remember it is ter minor.

[00:06:58]It is teras minor muzzle. So auxiliary nerve will be supplying to two musles.

[00:07:02]One is your deltoid muzzle. Another one will be the terus minor muzzle guys.

[00:07:05]That's all. So this is our golden rule here. And this will be helping you a lot when you will learn about all the five major nerves first of all guys. Okay. So now out of all these five major nerves first of all let's get started with the muscularcutaneous nerve. We are going to discuss all of them one by one. First let's begin with the muscularcutaneous nerve here guys. So the first major nerve that we are going to discuss right now is musculocutaneous nerve.

[00:07:36]Now guys make a habit here always whenever you're learning about any nerve any nerve first make a habit of writing the origin of the nerve from where it is beginning and then what it is supplying to and of course in the supply we'll be learning about the motor supply to the muscle and the sensory supply to the skin fine so in any nerve first of all make a habit of writing the origin first and origin I don't even have to teach you right now all my students are like expert we have discussed in detail in brachial plexus muscularcutaneous nerve will be originating from lateral chord.

[00:08:10]Lateral chord of brachial plexus. Can you just recall the pneummonic in your mind? The for the lateral cord it is L ML and there M stands for muscularcutaneous nerve guys. M for muscularcutaneous nerve. Then what is the root value guys? All the branches which are originating from the lateral cord the root value will be C5, C6 and C7. So therefore its root value is C5, C6 and C7 guys. Now after writing the origin the next thing to write down here is the supply muscular cutaneous nerve will be supplying to what?

[00:08:45]It supplies to all the muscles present in the anterior compartment of arm.

[00:08:54]Just now we have seen this in our golden rule. Okay. So muscular kitinius now will be supplying to all the muscles which are present in the anterior compartment of the arm.

[00:09:04]Now if you people have gone through uh the previous video where I have discussed about the muscles of your arm, forearm and the hand. Now you'll understand the complete purpose of that.

[00:09:12]Now you don't even have to mug up here.

[00:09:14]What are the muscles present in the anterior compartment of the arm? You have got your BBC muscles, corokchialis, the biceps and the brachiialis. So just write it here and finish it off guys. So therefore in the anterior compartment of the arm number one you have got the coroor brachiialis muscle and number two you have got the biceps brachi muscle.

[00:09:38]There will be a biceps brachi muscle and finally number three there will be a brachiialis muscle.

[00:09:47]brachiialis muscle. So these are the three muscles present in the anterior compartment of the arm. Understanding?

[00:09:53]So now my dear doctors if you just look at the screen here if you are properly following all my videos from the very beginning now I bet you I challenge you you don't even have to mug up anything here guys we already know the root value we already know the origin we already know the compartment and also we already know about the muzzles present in that compartment so it is just like you know combining everything at one place over here in the easy manner and there is no tension at all here no pressure here to mug up the things guys it makes sense Now in the supply we have just completed the supply to the muscles here guys. Ant anterior compartment of the arm muscles there. So now let us see the sensory supply also. If you have actually concentrated on the name of the nerve muscularcutoutaneous nerve musculo it will be supplying to the muscle.

[00:10:38]Cutaneous yes it will also have the supply to the skin also guys. There'll be even a sensory supply also. Now just look at me here. I'll tell you in easy manner here. muscular cutaneous nerve is going to enter into the anterior compartment of the arm. Now in the anterior compartment of the arm it will be supplying to corore brachialis biceps brachi and brachiialis muscle. After supplying to these three muscle it is not going to stop here. That muscularcutaneous nerve will actually continue into the forearm and it is the one which is continuing as lateral cutaneous nerve of the forearm. So it will be sublateral side of the forearm guys. Okay. So from today onwards remember it like this here. Musculo it'll be supplied to the muscles and arm and then cutaneous it'll be supplied to the skin in the forearm. So musculutaneous nerve musculutaneous nerve guys. Okay. So just mention there musculoutaneous nerve continues as lateral cutaneous nerve of forearm. You have to be like really careful with this one here sir. Forearm. Please underline that one. Muscular cutaneous nerve continues as lateral cutaneous nerve of forearm not the arm guys forearm I have seen some students getting confused over there so it'll be supplying to the muscles and arm but whereas the skin in the forearm guys that's all done that completes everything regarding the musculinous nerve okay so we have completed almost like everything about the muscularcutaneous nerve here guys the root value the origin the supply to the musles motor supply as well as sensory supply now after completing here everything regarding this one let me just discuss certain important MCQs which has been tested previously in the exams. So just write it like a note there. Note number one out of these three muscles out of these three muscle that is your corore bracalis biceps and brachialis muscularcutaneous nerve pierces one of the muscle and remember it is going to pierce the corcoalis muscle guys. So try to make a concept like this in your mind.

[00:12:36]Muscularcutaneous nerve is going to enter into the arm by piercing this coroccoalis muscle. It will enter into the arm by piercing this coroccoalis muscle. Guys, that is the first point to note. Now, muscularcutaneous nerve pierces corac brachialis muscle.

[00:12:58]Muscularcutaneous nerve pierces cororeialis muscle guys. Then next number two, one more thing which has been asked in your exams. Now please look at this diagram here guys. Just look at this diagram here. Now in this diagram you'll get a very very clear picture of you know muscular nerve how it is traveling the entire course of that first of all in this diagram you are able to appreciate here this one will be the auxiliary artery here guys.

[00:13:22]So this will be the auxiliary artery.

[00:13:24]Fine. And I have already told you auxiliary artery is the one auxiliary artery is the one with respect to that the nomenclature of the chords is given.

[00:13:33]I mean to say the chord which is present lateral to that lateral cord medial to that medial cord and the one which is behind the auxiliary artery will be the posterior cord. Now in this diagram you can you are able to see that this one is present towards the lateral side. So this is lateral cord here and this is towards the medial side. So this one is a medial cord here and the posterior chord is not visible in this diagram here. It will be actually present behind. So there is a lateral cord, there is a medial chord and then there'll be a posterior cord behind the auxiliary artery. Not visible in this diagram. Now recall about the lateral chord guys. Lateral chord is the one which will be giving rise to three branches that is L, ML branches. M for muscularcutaneous nerve. And now in this diagram look at this nerve here guys. Just look at this nerve here. That is muscularaneous nerve. That is muscularaneous nerve. And that is the one which is actually piercing this muscle. This muscle here will be the coroco brachiialis muscle.

[00:14:28]This is coroco brachiialis muscle here.

[00:14:31]And you can clearly appreciate there muscular nerve is piercing the cororealis number one and after that it is moving forward. Okay, moving forward.

[00:14:40]Then it is actually present between the brachialis and the biceps brachia muscle overlapping this one here. Now in this diagram you are not able to see the biceps brachia muscle. It has been removed from here. So just try to understand that the muscularcutinous nerve is going to continue between the brachialis and the biceps brachia muscle above. Now after that guys if you see this last part here you can see here it's not stopping here. The muscularcutaneous nerve is not stopping here and it'll further continue here and that will further continue as the lateral cutaneous nerve of the forearm.

[00:15:09]Lateral cutaneous nerve of the forearm.

[00:15:11]But what I want to you know teach you one more important thing here which has been already tested in the exam guys.

[00:15:17]Muscular kitinus nerve is piercing the corore bracialis and supplying the entire corbracalis muscle completely done. Number two it is supplying the biceps bracha muscle completely done.

[00:15:27]Then it is supplying to brachialis muscle but not completely guys. Remember muscularcutaneous nerve will be supplying to only like one half that to medial half.

[00:15:38]So it is just supplying to the medial part of the brachialis muscle.

[00:15:43]So the third one here the third muscle that is your brachialis muscle. Muscular cutis nerve is not supplying to the entire brachialis muscle guys. It is just supplying to the medial part medial part of the brachialis muscle. Then what about the lateral part? Just think like this here. Okay. So this is your humorous bone and humorous bone the shaft of the humorris behind that you'll be able to find the spiral groove. I I'm sure that every medical student knows this one. Now in the spiral group the radial nerve will be passing from here.

[00:16:09]The radial nerve will be actually taking a turn and going on the other side and here it will be supplying to the lateral half or the lateral part of the brachialis muscle guys. Understanding the radial nerve is the one which will be supplying to the lateral part lateral part of the brachialis muscle. So that is the second important point that you have to make note here guys. Yes. So please write down there brachialis muzzle and brachialis muscle you can divide that muscle into two parts.

[00:16:38]One will be the medial part and another one will be the lateral part of that and remember the medial part of the brach brachialis muscle will be supplied by muscularcutaneous nerve whereas the lateral part is actually supplied by the radial nerve guys.

[00:16:58]lateral part is supplied by radial nerve. Now what is the importance here?

[00:17:02]What I'm trying to actually teach you here is these type of muscles are actually known as the composite muscle guys.

[00:17:10]Composite muscle or else it is also known as the hybrid muscle.

[00:17:17]Hybrid muscle. So what is the meaning of composite muscle or hybrid muscle? It's a muscle which is actually supplied by two nerves. So you can clearly see here brachialis muscle is actually supplied by two nerves. muscularcutaneous nerve as well as the radial nerve guys. So if you wish you can just write down in short there what is the meaning of composite muscle? Muscle supplied by two nerves.

[00:17:41]A muscle which has to be supplied by two nerves and one of the best example of that is brachialis over there guys. So brachialis muscle the medial part of that is supplied by muscular cutaneous and the lateral part of that is supplied by radial nerve and that is the reason why it is one of the composite muscles in our body. There's a second point that you have to remember here. Now welcome to note number three. So basically after completing the topic of muscularcutaneous nerve I'm even trying to cover all the MCQs which has been tested in our previous exams and all every concept related to muscular various nerve guys. Now just imagine that this one here will be the lower end of the humorris and the lower end of the humorus will be having epicondile. There will be a lateral epicondile and then there will be a medial epicondile. Lateral and medial epicondile guys. Now in some people what is going to happen? The humorous bone will actually have an a bony spur here. A bony spur there. And from here what is going to happen? There will be a ligament. From this bony part there will be a ligament going and getting attached to the medial epicondile. Not always present. Okay, it is actually one of the abnormality.

[00:18:47]So what is the name of this ligament here guys? This ligament is said to be the struther's ligament.

[00:18:55]This is Struther's ligament. Now already this has been asked in the exam. What is this actually representing? Remember Struther's ligament is actually representing the third head.

[00:19:07]third head of corcoialis.

[00:19:12]Now Struthther's ligament is actually representing the third head of corcoalis. Now s what is the meaning of this one? Remember in the lower animals what will happen is the coroco bracialis muscle will be actually in the extended format. It will be having that third head also but it's not in the human beings. It is actually in the lower animals but in the human beings during development in some people what is going to happen? It persist. If it persist in the form of ligament and that ligament is nothing but truthless ligament.

[00:19:38]Getting it? So normally it is not a feature of human beings. Remember it is a feature of lower animals but in some human beings if it persist that then it'll be in the form of a ligament. That ligament is known as struther's ligament. So already it has been asked in the exam struther's ligament is representing what? It is actually the third head of corokchialis muscle. One thing done. Now if it is present then is there any problem here? Of course. If this truth ligament is present here then what is going to happen the median nerve can get compressed beneath that and not only the media nerve guys guys along with that one even the brachial artery I hope you remember the media nerve and the brachial artery will be coming here as a content of cubital fossa but because of the presence of this ligament what is going to happen here sir the media nerve can be compressed beneath that one leading to a syndrome and that syndrome is said to be the struther syndrome guys. Is it okay? So this is the media nerve here and this will be the brachial artery.

[00:20:40]Okay. And even this also has been tested in your exams like what is the most common nerve that will be involved in struther's syndrome and that will be your media nerve. Median nerve can be compressed in the struther syndrome guys. So basically this is also related to like corokchialis muscle present in the anterior compartment. That is the reason why I just wanted to finish off this concept also here also. Here only guys. Okay. So, better you just mention that last and final point here. What is the most common nerve to be involved in the truther syndrome? That is your median nerve. Just mention there guys.

[00:21:13]Most common nerve to be involved in struther syndrome.

[00:21:24]Done. So by this we have actually completed the entire muscular cuterian nerve guys. Not only like the normal supply, the motor supply and sensory supply. We have even seen like the MCQs which has been previously asked. So I want all of you to remember these three notes here. Note number one, let us just summarize here. Note number one, muscularcutaneous nerve is going to pierce cororealis muscle. Number two about the brachialis muscle being a composite muscle supplied by two nerves muscularcutaneous as well as radial nerve. And then number three remember about the struther's ligament and the struther syndrome guys. So that's all about the muscular cutinous nerve. I hope you all remember still our planning. We are discussing all the major nerves. So we are totally having like five major nerves. Out of that muscular cutinous nerve completed. Now let us go to the second one here that's axillary nerve guys.

[00:22:14]Axillary nerve. Now as I said you in any nerve first of all you write down the origin and origin my students are like expert. Axillary nerve will be originating from the posterior chord.

[00:22:28]>> [snorts] >> Posterior chord of brachal plexus. Now try to recall the pneummonic guys. What is the pneummonic for the posterior chord? It's lunar lunar and in this a here stands for the axillary nerve. Then what is the root value of the axillary nerve? It will be C5 and C6. Yes, we have seen that in the posterior chord all the five branches lunar branches we have studied about the root values in detail and remember axillary nerve has got the root value of only C5 and C6. Now after origin the next one will be the supply. It supplies to which muscles guys.

[00:23:04]Aillary nerve will be supplying to only and only two muscles. Number one it will be deltoid muscle.

[00:23:10]deltoid muscle that uh that beautiful muscle which is actually forming that rounded shape of the shoulder guys deltoid muscle and another one will be that muscle and in this again I'm telling you please concentrate on the minor it is tus minor muscle not major muscle I've seen many students getting confused over here so by this we are done with axillary nerve wow so if you follow my method here guys no tension at all no stress at all without mugging anything we already done okay now that is a supply only to the muscles now what about the sensory supply. Yes, remember axillary nerve will be actually supplying to the skin covering the deltoid.

[00:23:47]The skin covering deltoid. Now in simple words we can say that the aid nerve is applying to deltoid muscle as well as the skin covering deltoid. But guys how to describe this anatomically look here for example I'm sitting straight here.

[00:23:58]Now this is my deltoid muscle and the skin covering the deltoid muscle is over here. That means it is towards the lateral side of the arm. So that means axillary nerve is supplying to the skin on lateral side of the arm. But is it supplying to the complete lateral set of the arm? No, it is only supplying to the upper lateral set of the arms. Fine. So therefore, write down there a nerve will be supplying to skin over upper lateral side of arm. Upper lateral side of the arm. And if you are interested there guys, you might be wondering if upper lateral side is supplied by a nerve, what about the lower then? The lower lateral surface will be supplied by the radial nerve. I just told you the radial nerve will be taking a turn here. So radial nerve will be taking care of the of the lower lateral side of the arm. So coming back to our topic here, axillary nerve will be supplying to upper lateral side of the arm. Now try to understand the applied aspect here. Suppose if the axillary nerve gets injured. If there is injury to axillate nerve, then the person will not be able to sense anything from the upper lateral set of the arm. Okay. The person will not be able to sense anything from the upper lateral set of the arm guys. there'll be loss of sensation and that is actually referred to as the regimental batch sign. Regimental batch sign I hope you have seen in that army about the regimental batch and all. So they'll be wearing the batches over here here you know. So therefore the doctors have kept the name as regimental bad sign. So basically what is a nerve involved in the regimental bad sign? It is your axillary nerve. If a nerve is gone there'll be a loss of sensation in the upper lateral side of the arm.

[00:25:31]So better you do one thing here just write down there as applied aspect I'm writing in short as aa applied aspect in that regimental badge sign now what is this regimental bad sign guys regimental bad sign is loss of sensation [snorts] from upper lateral side of arm upper lateral side of the arm noise fine. So what is regimenal basine? It is nothing but a loss of you know sensation sensory loss from the upper later side of the arm. And of course what is the nerve involved here? It is because of injury of the auxiliary nerve guys. And this completes your axillary nerve also.

[00:26:15]So out of the five major nerves we have completed two of them that is muscularcutaneous and axillary. And now comes the most important ones that is your alnar and the median and the radial. All of them we'll be discussing together. Thank you.