Nerve Plexuses PDF

All right, this is the second recording and we'll be on the two more superior nerve plexuses. Okay, so nerve plexuses. What are these? They are networks or braids of spinal nerves, right? So here are spinal nerves coming out at each level. each level. Recall that in our thorax and add them in ther...

All right, this is the second recording and we'll be on the two more superior nerve plexuses. Okay, so nerve plexuses. What are these? They are networks or braids of spinal nerves, right? So here are spinal nerves coming out at each level. each level. Recall that in our thorax and add them in there. They're going to come out really single nerves and stay single nerves whereas in these specific areas they are going to form networks, right? form networks, right? So we're going to have several of these. There's cervical nerve plexus, the brachial nerve plexus, the lumbar, and sacral nerve plexus. So these are oftentimes called the lumbar sacral plexus as well. And importantly, they're going to be made up of those anterior rami of the spinal nerve. So if you recall, those are going to be the bigger ones that are going to come anteriorly and provide innervation to our hapaxial muscles, right? So there we can kind of see them all together. So really quick, I want you to think about why we might have these nerve plexuses. And I know on the PowerPoint you had the answers in front of you, but we want to make sure that these locations get the innervation that they need. So we have this really organized way that our axons are going to leave the central nervous system or go into. But we're also going to have these axons go through several different branches of this nerve plexus, right? So if one part gets damaged, there's going to be a likelihood that all that innervation will be cut off, right? So each terminal branch of the plexus is going to carry axons from several different spinal nerves. So I hope that kind of helps clarify why we have these. All right, so our cervical plexus. All right, so our cervical plexus. Cervical, you want to think of neck, right? So in the neck plexus. And we're going to really have a series of loops. It looks very overwhelming to begin with, but we're going to go through it here. So it's going to be comprised of the anterior rami of C1 through C5, right? Cervical 1 through 5. And we can see these spinal nerves coming off of cervical 1, 2, 3, 3, 4, and 5, right? So spinal nerves, specifically, we're going to think of those as the anterior rami. In red, we have the somatic motor branches, right? In red, we have the somatic motor branches, right? So we're sending motor to the muscles in this area. And kind of the big thing that we're going to pull out of this is the anso-cervicalis nerve. And anso-cervicalis is going to be this loop in the neck of nerves. And so if you kind of follow that, it's going to come down this way, and then back up this way. So this is going to provide innovation to the genial hyoid, and then also all of the infra-hyoid muscles, okay? So this anso- cervicalis is providing innovation to the infra-hyoid muscles, which we know are going to help move the thyroid as well as the hyoid in terms of speaking and swallowing and things like that. So pretty important. I have a question. Why is the genial hyoid randomly part of this group? And we're going to talk about it here in a second, right? The genial hyoid is the weird one out. We also have the phrenic nerve, which is going to be our diaphragmatic nerve, right? So it's going to go to the diaphragm, which is pretty important for keeping us alive. So C3, C4, C5 keeps the diaphragm alive is what we're going to think of for that. So if we look at on this right here, we can see that C3, C4, and C5 are all going to contribute to this nerve down there, right? So if we know this kind of thing, and we can look at this image and say, all right, well, which nerves are contributing to these? C3, C4, C5 keeps the diaphragm alive. And just recall that these structures are bilateral. We will see them on both sides of the neck. So there's our motor innervation. So there's our motor innervation. You can see the anciservicalis giving off innervation to all these muscles here. All right, here's a look at it at what it would look like in a very nicely dissected donor. So here's the hyoid for reference, right? So here's the hyoid for reference, right? Here are our infrahelioid muscles right here. We can see this beautifully dissected out anciservicalis, right? So that is going to go back up. It actually does this really neat thing where it hugs the internal jugular vein right here. We also can see the internal crud, external carotid artery actually right here. So this is going to be, I actually think, yeah, so that the internal jugular vein and our carotid artery portion of it is coming up and out. So the anciservicalis is this structure here, and you can see it, oops, giving off nerves directly or innervation directly to these muscles here. And so why does that geniohioid, why is it part of this group? Because, so cool, it's from the same cervical myotome as those other muscles, right? So geniohioid, weirdly superhioid muscle, right, but it's going to come and it's going to migrate from the same myotomes as the infrahelioid muscles, right? So that's kind of our important link between our development and what we see. All right, so the cervical plexus here, we're going to go on to the cutaneous somatic sensory branches, right? So the ones we see here in blue, you can see they're widespread, are going to provide our sensory innervation from the skin, right? And they're going to be named for basically where they go, right? So you can see C2, C3, and C4 are going to bring this information in from these different areas. If we identify these from superior to inferior, we're going to have a greater auricular coming up into the ear, right? The ear is an auricle, the outside flappy part is called the auricle. All right, we have our lesser occipital. You can see that coming back this way. I should do it in black, not blue, because motor is blue. There we go. We're going to come back. So we're going to have the lesser occipital hanging out back here by our occipital bone. And then the transverse cervical across the neck nerve. So there we go. It's going to come on out across the neck nerve. And then we are going to have the suprascapular. So you can see that one coming down and spreading out to the skin that's just above the scapula, right? So using our anatomical terms that we already know, like clavicle and occipital, those bones, right? We can kind of guess where these might traverse. When you move on in your education, if you move on to medical school, then you're going to have to know what spinal nerves from C1 to C5 contribute to these. We're just sticking with identification today. All right, so here is a cool view, right? So those spinal nerves are coming out of the cervical vertebrae, which are going to be deep in here, right? So we have our vertebral bodies in here. We have our posterior root and our anterior roots coming together to form a spinal nerve. And then we have a nice big anterior root coming off, which is going to join up and create these. Here we have our lesser occipital coming up to, we've got to change the color again, up to our occipital bone, right? So there we go, with our greater auricular setting up branches near the ear. Then we have our transverse cervical going right across. All right, this is actually our external jugular vein here. So there we go, it's sandwiched between the sternocleidomastoid and our jugular vein, external jugular. And then our suprascapular right there coming on down. And these nerves will be pretty superficial, just under the skin here in terms of where they're at. All right, the brachial plexus. I know this is like the vein of many people's existence, but it does a lot and we need to know it. So for our purposes, we're going to look at the actual nerves, where they come from, how to define those branches or those segments, and then the terminal nerves that go into the upper limb. I'm not going to ask you to identify where, for example, the radial nerve is coming from in terms of the spinal nerve. So I'll let you do that later on in life. So we're going to have cutaneous and motor innervation carried in these nerves from the upper limb and pectoral girdle, which we know those muscles now, right? At least we're learning them now. It's going to come from C5, C6, C7, C8, and T1. Remember, there's C8 because our first spinal nerve is going to come up above the vertebra, the first vertebra, and then we're going to have C2 coming down below the first vertebra. So we have kind of an extra nerve here. They're going to go under the clavicle. So we can see in this image here, if we pick up the clavicle or go deep to that, that is where we're going to find our brachial plexus. It's going to travel over the first rib and then into the axilla, which is our armpit. You can see those actual nerves right here coming from C5, C6, C7, C8, and T1. These two merge together really quickly. Okay. So as we work through those, so we're going to think that the body is over here. This is going to be the armpit area here, right? C5 through T1 are located here. There are smaller branches that come off more approximately towards the body. Before we get to the muscle, the nerves that we need to know, we're not going to focus on those now. All right. So each of these kind of segments of the brachial plexus are going to be named something. So we have our roots, spinal nerve, anterior rami, right? Our trunks are going to be named from superior to middle to inferior, where they're located to one another. Divisions are anterior and posterior. All the posterior are going to come together and two of the anterior are going to come together. And then we have our cords. The cords are nice and neat because they're actually named for their position around the axial artery that runs right through here. So the posterior is behind it. Right. And then we'll come to our terminal branches or our peripheral nerves here. And these are the ones that we're going to follow into the arm. One of the helpful aspects of this is going to be this down, up, and down. Oh, I do actually expect you to know the peripheral nerves. What we won't focus on is what spinal nerves contribute to the lateral cord, the posterior cord, the medial cord, all the way back. All right. So we do want to know these. That'll help you out, I promise, in the future. Our M helps us because we have our musculo- it's really easy to identify. We have our musculocutaneous nerve, our median nerve, and our ulnar nerve helping make up that M. And then the other two nerves are axillary and radial. Okay. So we are going to go here and kind of identify those, right? So our anterior rheumae are just these structures here. 5, 6, 7, 8, and T1, right? And then we're going to have our trunks. So we're going to have our superior trunk, our middle trunk, and our inferior trunk here, right? We have other nerves coming off that we're not going to talk about this year. Then the next thing we have is going to be our divisions, our posterior divisions are all going to come together and form the posterior cord here. Our anterior division of our lower or inferior trunk is going to come on and just be its own thing here. So anterior division is going to become the medial cord here. It's more medially closer to the body. And then we have two anterior cords here, anterior cord. Here's this other anterior cord. These two cords from the superior and middle trunk are going to come together. Anterior cords to form the lateral cords, our anterior divisions from the superior trunk and the middle trunk will form our lateral division here, lateral cord, excuse me. So the neat thing is when we get into dissection, what we're really going to see are really from here on, unless we really dive in there and get really deep right in the neck. So at this point, we have our lateral, posterior and middle cords all surrounding a nice big artery that runs through here. And those are going to make our terminal nerves, right? So here we have that nice M that I talked about. So this is the musculobutaneous, this is median, and then this is ulnar, just like our ulnar bone is closest to the body. Pretty cool. And then we have our axial right here. And we'll have our radial nerve right here. So I'm going to ask you to practice this and draw this out, right? All right, so here's another view here. And we're going to talk about what these nerves do in general, these big themes. There's always little details in addition to these as well. So we're going for big themes here. So here's our M and the knot M thing. So we're going to do the knot M things first. So the axillary nerve is going to stay on our axilla and run behind the head of the humerus. And innervate, importantly, our deltoid muscle and our teres minor muscle. So our deltoid muscle, which is going to help abduct our arm and our teres minor muscle, which is going to help with lateral rotation, are innervated by this. And in terms of sensory, it'll be skin over the deltoid. So pretty straightforward with that one. So axillary, we'll do that, that color. Our musculobutaneous nerve. I should do radial and ax. I'm going to do radial and ax real quick here. So radial nerve, again, not part of the M, is going to come on down, come on down, and radial nerve runs away, right? Radial nerve is going to come down and shoot in posterior to the humerus here. We're not going to see it for very long. So radial nerve runs away and is going to wrap around the lateral aspect of your arm. We're going to see it again anterior to that lateral epicondyle of the humerus. This is going to be clinically important for us. That is going to provide a lovely big pattern here, posterior upper limb, right? So posterior compartments of the arm, posterior compartment of the forearm. So we're looking at all extensors. So radial nerve is going to do extensor muscles. So that's a really nice big theme here. It is also going to do the skin over the posterior arm, forearm, and most of the hand. Okay, so most of the hand here. Going back to our musculocutaneous nerve here, let's do it in, I don't know, green. Let's go for it. There's green. We're going to have our musculocutaneous. It's going to be the lateral most branch of this M, right? So here's our musculocutaneous. It's going to come on down as it comes through the arm, anterior to the humerus. It is going to provide all of the anterior compartment muscles of the upper limb. So brachialis, coracobrachialis, and biceps brachii, right? Muscles are going to be innervated by the musculocutaneous. So that means all of our flexor muscles in the arm. As it moves on down, it's going to send branches to the cutaneous region, right? So it's going to do all the sensory. It's going to do the sensory of the lateral forearm. We'll see this kind of pattern with these nerves that they're going to provide motor first. And as they continue on down, if they continue on down to certain places, and then they will do, they will innervate the skin, right? So motor first, skin next in terms of proximal to distal. All right, we've got two more to go. So here's our structures here. We're going to do purple now. Here is that radial nerve running away. We can see it coming on down. It's going to split. It's got a superficial branch and it's got a deep branch. We'll get to those. But our median nerve is this one here, part. It's going to be the middle part of the M, median, like a median on a highway. It's going to run down the middle. It's actually going to run with our brachial artery here, which we'll get to next semester. So if we have damage to the median nerve in the arms, usually that's going to affect the brachial artery. It's going to come down right down the middle of our forearm, of our cubitophosa here. Of our elbow joint and go on through the forearm all the way down into our hand. And it is going to provide innervation into the hand as well. So the median nerve is going to provide motor innervation for the large majority of the anterior forearm. So these are the flexor muscles of the forearm, right? It's also going to supply the thanar muscles. So those ones around our thumb, we're going to have a branch that comes back. It's called the radial return to come back. Also, two of our lumbar goals and our lumbar goals do that weird thing where they flex at the MP joint here and extend at the pip in the dip joint. So it's a weird thing that if I was in person, I would shoot you. Okay. So the lumbar goal is for two and three. So that means digits right here, two and three. And then sensory is going to be on the medial side in general, right? So medial skin on the wrist and the hand and then half of our hand, right? So digits two, digits three, and then weirdly half of the fourth digit here. So that is going to be where our median nerve is going to provide sensory innervation. All right, ulnar, here we go. We'll do it in blue again because we are on a different side here. Ulnar nerve is our funny bone because it's tracing. So it's the last part of the end, the medial most part of the end. Going to come on down and it's going to wrap posteriorly around the medial pecan dial, right where all of those flexor muscles are going to come from and go that way. So here's going to come on down. If you ever hit your funny bone, you're hitting your ulnar nerve, right? It's not that funny when you hit it because it hurts. Come on on down here into the hand. So the ulnar nerve is going to be the odd one out in terms of the muscles of the forearm. It is going to flex or innervate the flexor carpioneres, which I hope makes sense because it's on the ulnar side, right? And then half, the medial half, right? Like our ulna of the flexor digitorum profundus, right? Which means the flexion of those most distal portions of our fingers are going to be innervated by the ulnar nerve, right? So flexor digitorum profundus. And then also, in addition to that, all the other muscles of the hand. So that means the hypothanar muscles, right? Hypothanar. Thanar is median. Hypothanar muscles. That's also going to include our intraoscii muscles, both the palmar and the dorsal intraoscii, which help us A-B duct and A-D duct, our fingers 1 through 2 through 5, right? So everything else, and also our lumbar goals for 4 and 5 here in the hand. So most of the hand is going to be innervated by the ulnar nerve, except the thanar muscles. Most of the arm, or forearm, is going to be innervated by the median nerve, except two things, flexor carpioneres in half, I should say one and a half things, and the medial half of flexor digitorum profundus. All right. And let's see. And in terms of sensory, the anterior and posterior half aspect of the medial hand. So this part of the hand, half of the fourth digit, and then on the posterior side as well, digit 5 and half of 4. All right. Here we have everything kind of just spelled out a little bit more straightforward, right? There are some details, of course, that we know. And here's kind of a nice image of where these like dermatomes are located, where we have cutaneous sensory innervation to the skin. Axillary isn't on here, but it'd be just like that. Okay. There's axillary where that would be. So if we're talking about axillaries there, musculocutaneous then is going to be here. Median nerve is going to be orange. So I'll do a big N maybe. And we can see it's a little bit weird in the fingertips here. The ulnar nerve, right, is going to be right here. So the medial stuff, medialmost stuff, then radial nerve, generally just the back of everything, except where the ulnar nerve is, right? So big trends for these. All right. And this is just an image here. I am going to make a separate video, and we're going to talk about the brachial plexus as we would see it in the donor here. All right. All done.