Peripheral Nerve PDF

Week 8 Brachial Plexus Lecture 1 Service systems, we're going to look at the upper limb and the lower limb and then I'm going to introduce you ever so briefly, but I will introduce you to the autonomic nervous system, which is technically part of the peripheral nervous system. So in humankind, per...

Week 8 Brachial Plexus Lecture 1 Service systems, we're going to look at the upper limb and the lower limb and then I'm going to introduce you ever so briefly, but I will introduce you to the autonomic nervous system, which is technically part of the peripheral nervous system. So in humankind, peripheral nerve problems are most frequently encountered in the upper limb. The number one mononeuropathy in humans is the so-called carpal tunnel syndrome, which is the median nerve entrapment at about the region of the wrist and that's worldwide. The statistics are are fairly consistent #2 is all N at the elbow #3 is alnar at the wrist of the so- called. The rest are pretty rare. Now the lower limb is even less common. But we do have polyneuropathies due to diabetes worldwide. That's number one call. And also other disorders, systemic disorders. You can read havoc on the peripheral nerves. So the upper extremities we're going to spend a little bit more time on than the lower extremity. And again, we'll come back and talk about some of the conditions as we go along. So the study of human anatomy has been around for ages, as you can see there in that that picture. And we're so blessed to be able to study humans and. Have cadaveric tissue or even photos and videos these days for us doing things online. So it's a real blessing to be able to have that because there's nothing like it when you see it. And I know we're an online program, but it's a really neat thing. If you ever have the opportunity to do it, you should. We're actually working on a few. Continuing Ed programs at the university on weekends where you can come back and and do these lot. So let's take a look at arguably one of the most important structures in the peripheral nervous system. And this is called the brachial plexus. Now plexus means a group of nerves clustered, running and clustered together. Is Latin for arms, so this is the plexus of the nose in the arm. Now you can see that nerve root C4C5C678 and T1, sometimes T2 as a as an anatomical variant, but these are the nerve root levels that form. Plexus Now the brachial plexus comes down diagonally as you can see here, and the highly mobile shoulder joint lends itself to create quite a few great deal plexes problems. Quite a few brachial plexus injuries due to the excessive mobility. In general compared to other things. And so there's a lot of shoulder problems and problems that we encounter, everything from a good old-fashioned whiplash injury. You know, we see people sitting still in the construction zone on the Interstate. And so they did some doing 75 those types of injuries with a three-point harness safety. Stretching on the brake pedal plexes. So the brachial plexus as you can see here gives rise to all the major nerve branches and these nerve branches are the median on our. These are the three main. We'll talk about it as well. And here's a category photo. You can see some of the structure from the great places. So we use a pneumonic. We don't use a lot of neonics, but we use this one. Real teachers drink cold beer. So this is room. Division. Cord. And then branch, which is another way of saying that the real teachers drink with beer and you can see the roots. These are the nerve roots C5678T1 and then the trunks. Are seeing here and then we have chords. Now I'll tell you what is the most important thing clinically is knowing the brachial plexus, but the cords. The cords are where we see stretch injuries and so-called traction injuries and the medial. Because of its tension. That medial cord has in those stretch and that's what we see most of the injuries and therefore the knee joints break their cutaneous nerve, which is in English written as medial companies #4 right here on my first. So we have the lateral cord. So if in the anatomical position is such so lateral or medial cord and then in the back posterior cord. And of course the posterior cord would innervate the triceps and deltoids things that are posterior. So that that makes a big di[erence. Let's start out with the median nerve. And the median nerve is very, very important nerve because. It is the the main nerve that innervates our flexor compartment. And of course humans are very flexible oriented. I would much rather have the ability to flex my wrist, my forearm, my fingers and right then extend. I could, I could conceivably mechanically. Get this writing utensil out. So arguably flexion is the most human of all motions. In fact, it is, and primates as well. So it's a very, very important nerve. Now, interestingly enough, the median nerve arises from the lateral. The medial cords coming together, so axons from the lateral cord you see up here and the medial cord you see here, they come down and they they merge and they form this median nerve. Now the median nerve gets its name like the median of the highway in the midline of the forearm. Now what's interesting about the median nerve is it doesn't do a darn thing until it gets to the antecubital or the cubital region. And so you see it does not provide any sensory modalities. It doesn't provide any muscle innervation until there is just distal to the elbow cubital region. Now it runs with the brachial artery and the basilic vein. We call this the neurovascular bundle. And they run together, right? And so. And then right as it passes the elbow joint of the cubital region, it innervates the pronator terries, the flexor carpi radialis, palmaris longus, flexor digitorum superficialis, so flexor digitorum muscles. That, they're trying to argue, makes a good amount of sense. So flexor of digits, superficial, flexor, digitorum, superficialis. Now here's the trick. That's easy enough, but the trick is that once you go about 1/3 of the way, 1/4 of the way distal. We have a purely motor branch of the median nerve called the anterior interosseous nerve. Now it gets its name because there's an interosseous membrane between the radius and the ulna, and this is obviously anterior to it. In fact, it literally lies on the membrane. It's. So it's it's very, very deep. It's protected by all these more superficial flexor compartment muscles. So it's very rarely injured. That's a really good news. But the deep flexor component of this median nerve is called the anterior interosseous nerve. And it innervates flexor pollicis longus. Remember anatomy policies is thumb. It innervates pronator quadratus, our power pronator because pronator terries up here is our weak pronoun. It's more of a proprioceptor for that pronation supination action and then flexor digitorum profundus. That means flexor digitorum profundus which flexes the the proximal interphalangeal joint, not the distal. And excuse me, the distal flexes the distal joint and the flexor digitorum superficialis. It's the power grip. And if you go grab your, your suitcase, you know, you go to the baggage claim at the airport and rolling around the carousel, you reach over and grab the handle. You choke o[, don't you? You use, use the proximal interphalangeal joints and that superficiality. That's the power. So like this, this additional information and what's unique about this scenario, you'll see this black and white square here that means there's dual innervation. So these. To the index and the middle finger, the distal interphalangeal are innervated by. The muscle that acts on them is flexor digitorum, but not superficialis. It's very deep, right? It's very profound. So it's all provided. And so that is innervated by the anterior interosseous nerve now. If you look at the. Flexor digitorum profundus of digits, the middle or excuse me, the ring finger and little finger, the 5th digit. That's all of our innovative So flexor digitorum Pro funded, which is a flexor of your 4 fingers, not policies, just just just. And it flexes the distal end flanges just like that. So the first two makes sense medium which is. OK, now the median nerve. Not the not the deeper answer interosseous nerve, but the median nerve travels relatively superficial. And travels through the famous carpal tunnel and innervates several muscles, the so-called tenar eminence. And we'll come back and look at those hand motions as well. And this is at Doctor Paul's brothers, Flexor policies, brothers. Upon impulses and the 1st and 2nd lumbrical, everything else in the hand is innervated by the owner nerve, right? So let's be clear, there are no radial innovative hand muscles. There's radial innervated muscles that act on the hand, but intrinsic meaning. With the hand muscles, the intrinsic hand muscles were the scenar eminence are median nerve to the rest are all hallmarks. Here's another easy thing to remember about hand muscles. They're both both sides that's seen on the hypothenar, so the median and the old. Group of muscles as well. They all share the nerve roots. CAT1. CHT, one nerve root, hand muscles, whether it's media or or not, we can see another illustration. I always like to have di[erent viewpoints from di[erent texts and things, di[erent reference books. And you can see the lateral and medial cords coming together right about here, forming what we call with an M shape here. And then that's the median nerve and there's the various muscles that are interface. You can see the anterior interosseous nerve branching o[ here. As long as Fletcher would be fun for fun this information the the traditional or non traditional, but the the superficial division of the median continues on out through the carpal tunnel and invasive enough in there. So that's why when you see these people with carpal tunnel syndrome. I see them in their 70s and 80s and they've had it for 40 years. They have nothing on it. There's total atrophy of muscle. Let's start of our victory is the ulnar nerve and the ulnar nerve. Is really the intrinsic muscle nerve for the most part now it comes out it, it acts on Siri or or come out from if you will from the C8T1 nerve root. They form the medial cord of the breakfield plexes. They continue on around the ulnar sulcus, this epicondylar. And they go under the flexor carpi omaris, as you see here, and they travel out between the hook of the hamate and the piece of form through the so-called canal of someone. And they have a palmar branch that goes across and innervates all the intrinsic hand muscles other than the ones I mentioned previously. Muscle and the interosseous muscles. All the interosseous, specifically both dorsal and palmar, innervated by the G. You can see the sensory distribution of the owner nerve is digit 5 and the former side if you will of doing finger. The ring finger is dual innovator that's why it's the ring finger represents in most cultures. And So what you see is here. Renovation, let's go back. There is a median nerve sensory distribution. I skipped over that kind of quickly and you can see that over here on this portion, the thumb side or the so-called radial side proposition that that half of the median and the other half. The radial nerve is very interesting nerve because this derives from the posterior cord. It gives rise also before it. The posterior cord gives rise to the so- called axillary nerve, which gets its name from the asteroid and is. And so the radial nerve is very, very posterior nerve. To travel. Underneath that actually kind of through your axle and those around the. Kind of the mid shaft of the humerus, in fact it's laying on a little groove in the bone called these spiral groove. So mid shaft humeral fractures which are not uncommon, they almost always damaged, they lesion the radial nerve. So we see that. And then of course, the nerve comes around, branches o[ into a deep radial division. And of course, the superficial radio is o[ensive. But it innervates the extensor wrist extensors and sensors. So let's go through a few of these muscles in this presentation. Certainly it's not all inclusive. This is more introduction level. We're going to go into, we have a course in our masters degree programming personal nervous system. So this is kind of a winter level anatomy. We'll delve into the anatomy a little bit deeper. We'll delve into neurodiagnostic to the peripheral nervous system. We'll start out by a little kind of do a little assay if you will, a little review from head to toe and we'll look at the deltoid muscle. So you'll see my slides and again, these slides are I always include them on our weekly page on Blackboard because. There is a resource as the textbook, vacation textbooks. So not just me as a talking head on the video, but you have this as a resource and download all these, download everything that you get in in this program because when you do the capstone course, I think I've mentioned this before there, there's mentioned again when you just ask. It's a big review, some of the review of the whole program, which is very typical in that program. It's not all it's not to sit down. It was a written exam. Many of the questions are the same questions. Scoping. But that's a lot of people saying, I think remember downloaded these, please do download them all this for your personal use, not please e-mail. So you can just look at the origin and the insertion and the action of these and the innovation is important too. And of course the deltoid muscle AB dot V R&D. After the 1st 15° and this is largely innervated by axillary nerve, it's considered mostly found nervous. Now remember in peripheral nervous system and in our limbs there's not. Muscles that are only one nerve root level. And in fact it's called flurry, segmental innervation, and our designers did that. So we have a backup system. So we have C5 for the deltoid and of course that's just a bit of the muscle on the shoulder girdle. Some areas of anatomical spaces, here's the structure called the triangular space and the triangular space has a couple things. One of them was circumflex scapular artery and you see the quadrangular space and that's where the axillary nerve comes out and it comes o[ the posterior cord and the axillary region, hence its name and then an interface. And one of the branches goes up and innovate container is mine. On the. Then there is a triangular entry hole, which is not a natural space in an interval, is there? And anatomical planes, you have to separate it out with your probe laboratory, but in the triangular shape. And so it's a triangular interval between the long and the lateral head of the triceps and that's where we can. Biceps brachii, of course, is well known. It's 2 heads. That's that's its name. And it flexes the elbow. You can see that it has 2 heads up here really high, and it's got the long head and short head along. The long head originates from the Super glenoid tubercle, the scapula. So it's actually above the joint on the scapula and the short head. Process of the skin and of course they insert distal to the elbow and then the so-called radial tuberosity which causes elbow flexion. And then there is the musculocutaneous nerve. The musculocutaneous nerve is one of the least injured nerves in the human body. Protected it's actually underneath this bicep break and the spinal nerve root level. Whenever you see in my scheme of things, I use bold, bold and under underlying that means the the reference is also the majority of the contribution in this case is. But there is some C5. So if you clip the C6 nerve or in the dramatic injury, would I have any sort of action of the biceps breakdown, the answer is yes. You probably weren't. It would be weak when you receive tremendous amounts of that atrophy. But some of those axons do get some of their innovation. So the musculocutaneous nerve, I mentioned to you here just briefly that it is a very well protected nerve and it is derived from the lateral cord. So if you get in this, you get in the anatomical position I know on this, this. Dark background, it's hard to see. Who were dark, so it doesn't reflect o[ under any images in the unit. And sometimes it gets talking head. But here we are in the anatomical position. And if you look at this, the lateral pretend the biceps is up here. That's kind of lateral, isn't it, relative to the humans. So that's how I kind of remembered it when I was first exposed to that. And that is the musculocutaneous nerve. And you can see that it's underneath the contractor, underneath devices for FBI. One of its major trucks traveling distal underneath that bicep muscle and this has caused the lateral antebrachial. Now the words antebrachial like Brazil. This takes. And you can see that here. Now we're going to see. Which is very clinically relevant. Can you break your plastic? We'll continue on from here. And you see the triceps break the eyes here and there's a lateral, you know, looking at this in the first year of youth that's lateral versus medial. So that's the lateral head. And you can see that radial nerve is well protected by the muscle, but it is very, very intimately close closely here. This so-called spiral grooves. And there it is looking at it from this anterior position in this, this, this, this illustration is basically like I am positioned here. So you can see the brachial artery. You see the basilic vein where they tie it would be the the soic vein. There's the median nerve right here. And that's going to be the owner nerve. We don't really see the radio here too much. Medial head of triceps, long head and arrow heads. Not really seen in this particular picture. And the triceps is considered clinically even though I have it bolded and underlined as C7 N 8 is considered a C6 bellwether test C6 bellwether. So C6 nerve root if it's working well, your tricep. Radial nerve innervated muscles should be working well. So let's move on and let's go take a look at the interior form. Now what I'm going to do for simplicity, if there is such a thing. And by the way, the lower limit I think are easier than the upper left. And it's largely because the lower limbs are more distinctly di[erent in their compartment. So for instance, the anterior lower leg has one nerve for every muscle, one artery that supplies every muscle. The lateral compartment, the posterior compartment, they all have one nerve, one major nerve root, and. One blood vessel, one blood supply. The arm isn't like that. So it makes it a little bit more challenging. However, we're going to break it down into two layers. We're going to break it down into a superficial and then a deep layer. So we've already talked about the forum to some extent. And so remember the pronator Terries, which is just here just. Distal to the elbow, flexor carpi radialis. So it flexes carpi means wrist, flexes wrist and it's inserted on the radial side. That means the radius palmaris longus, which is a tiny little feather like muscle, very short, but it has a long tendon down the middle line that you see right about there and flexor carpi. These are the superficial layers. Now you notice there's di[erent color. There's a yellow line. These four things number thumb is no longer called sun is what the sun is policies just like the toe is how the great toe is houses. This is policy so Fletcher digitorum superficialis flexes the proximal. Join our power. So why did I make these di[erent colors? Well, here's why. The yellow. Is innervated these yellow muscles? The pot being yellow is innervated by the median nerve and flexor. Carpi Omaris is in a very by watch. Ohh man makes sense. It's called the mirror. Ohh, like that you're not all that simple and that intuitively obvious, but this one is. Now let's go to the DVD player who innervates the deep flexor compartment. It's the deep pure mode of branch of the median nerve called what? Anterior interosseous. Anterior interosseous. It's something. Surface of the interosseous membrane. And it innervates 3 the flexors flexor pollicis longus, flexor of the thumb, pronator quadratus which runs a band like muscle across for pronation and flexor digitorum profundus which flexes the distal interphalangeal's like that. Half of that is. And the other half is former innovation. So if you slice somebody's median nerve up here, let's say the guy works in a sawmill and fall in the blade, cut his arm o[ o[ and he lived six months later, you know, slices medium there, but not his own. Hypothetically. This is what he would do. So he would be able to. What's that? All the preachers signed the benediction sign, but the path will sign like the Pope brushing my son like. So why? It's because these two digits, the range and the little finger, the flexor digitorum profundus muscle received their supply containers, but in this case actually online and if the owner wasn't damaged, that would still work. That's what you would look like when I say. Put this rubber ball in your hand and squeeze it and it would be like that. It's hard, it's even hard to do. OK, so pretty profound injury. Imagine, no pun intended. So protein arteries, let's take a look at these deep flexor muscles. The pronator terries is really our our weak. Our weak pronator is not stu[ to start out with like flexors that are superficial and we see it right here. So it originates from the medial epicondyle and then it. On the humoral head, and then it goes over some of it's from the coronoid process of the ulnar head and it inserts midway, Midway. I say, wow, that's all the way down, halfway down the radius. It's a lot further down than it looks with these other fascial planes and muscles over top of it, but that's it right there. Diagonally, so it's a weak pronator. It certainly is a weak pronator and there's a lot of muscle spindles in this muscle. So they think it has a lot of proprioceptive feedback for fine motor control for the upper limb and of course it's median nerve. It's in the flexor compartment. It's median nerve. It's C6C7. There's a little debate on that. It's pretty close. We go with C7 and electrodiagnostic diagnostic world. Of course it's a It's a weak pronator of the two. What's the power pronator? Profundis. Sorry, Pronator quadratus, which is. So the flexor carpi radialis is another one that's superficial, isn't it? So what does it mean? It flexes the wrist and it's on the radial side as you see here. Let's bring in some anatomical cadaveric photos. And the flexor carpi radialis is unique and the Everlast once I remove the skin on the bowler. It stands right out. You have anti cubital fascia that's really tough. We clear that away. We walk in and say, all right guys, gather around. Let's take a look at this guy. What do we see here? See this big white very much. Like a strap, like looking tendon. That's always the FCR flexor. Carpi radialis. It's a power flexor of the wrist with a little bit of a radial deviation. When you flex the wrist it radially deviates. Any origins the medial epicondyle and inserted into the base of the second and third minute carpal and of course it's a superficial flexor compartment and muscle. Therefore it's median nerve and it is unequivocally largely a C7 nerve root level muscle. And you can see when you work it together, when it Co contracts with flexor carpi onerous and flexor carpi radialis fire together, you get a strong wrist flexion without a lot of Omar or radial deviation. So it's a very much these two guys. They really stabilized the hand in flexor positions. Palmaris longus, Well, palmaris longus is absent in about 10% of females and even absent some males, but to a very small percentage. And you can see this muscle over here is a very, very tiny looking feathery looking muscle. Long thin tendon. OK. So flexor carpi radialis is more of the radial side and palmaris long as it's running down the midline here, it actually is very interesting. It inserts into the flexor retinaculum and the palmar aponeurosis. So the flexor retinaculum is a tough connective tissue sheet. That covers our flexor tendons, these synovial sheaths, if you will. These tendons are very, very fragile. They call this area surgical no man's land. For that reason. You don't want to get cut in here. You can ruin these tendons. And this app on the roses really keeps us, gives us a level of protection and an added level of protection. So what we see then is. It's innervated by the median nerve. It actually inserts into the flexor retinaculum, which is the roof of the carpal tunnel. So the idea is that maybe it keeps a little tension up in nerve and when it does its job, maybe that's part of why Someone Like You don't have carpal tunnel syndrome. So this is median nerve. We mostly say C7 and C8, mostly C8 flexor carpal narrows. Who innovates it? On our gives it away right flexor carpi. On theirs it's in the flexor compartment of the forearm but it's innervated by the owner nerve. Don't let that trick you up. Spinal nerve root levels C7 and C8. What does it do to flex is the risk hence its name flexor carpi ulnaris and it studies the risk when it Co fires. Co contracts with flexor carpi radialis. All right, last of the superficial muscles is flexor digitorum superficialis expeditious. Too young for that. I think it was Mary Poppins. I'm even almost too young for that. So flexor Digitorum, although I did see it in the theater when it first came out. I do remember that. Flexor digitorum superficialis. So what does it do? It flexes the fingers. And it is superficial. I love anatomy names When when they when they have a plan like flexor digitorum, profundus. Where's that? Is that in the superficial layer or is it in the deep layer? It's profound. It's deep. You're a profound guy, you know? Or you know, you said a profound laceration means it's deep. So flexor digitorum superficialis is a superficial flexor and all of this red looking tissue, this muscle tissue that you see here with these tendons over top of it, the bulk of what you see in your forearm. Is this muscle? So it is a strong, let's get that in the box. It is the power grip muscle. And of course it's good old plain old median nerve because it's not entering crosses. Is it why it's not deep, so why would it be entering? And it's a C8 innovation. Now back up for a second. What does it do? It flexes the wrist. Yeah, but what else does it do? Well, it's main job is its name. It's a flexor of digits and it's superficial and it inserts. Just distal to the proximal joint. So it's the power grip because it makes our fingers flex at the proximal joint. But because it crosses the wrist, it still is a wrist flexor, isn't it? In fact, it's dumb go as far as to say based on looking at it by itself in this illustration versus flexor carpi radialis and what I've seen for years in anatomy lab. I think it's it's probably the the more powerful than two flexors of the wrist because it flexes the fingers. OK, why? Crosses the wrist joint anytime a muscle or its tendon or tendons cross a joint. Probably act on it, isn't it? So it does it acts on two thing even says it there, doesn't it? Maybe, maybe not, but it does. So let's go to the CD player. There's the word profundis or profound. So it's deep flexor digitorum profundus. There it is. Everybody's superficial's been removed from this illustration. And this cadaveric picture, this cadaveric photo. Has all the flexor compartment, the superficial flexor compartment muscles removed. See the see the the lines up here. You can tell that that tissue has been transected and removed away. And look right down here. Here's the carpal, the wrist bones, carpal region, this is the carpal tunnel and the flexor retinaculum, this connective tissue covering of the carpal tunnel has been removed and we see tendons of these deep flexors going into the wrist, so flexor digitorum. Flex is what distal interphalangeal which is not very powerful. You don't pick things up with your the distal fingertips, you pick them up with your proximal. Don't you? And who intervenes it and tear interosseous nerve for these two think median anterior interosseous nerve here. Over here is more all right. So think owner for those two. It's our first dual innervated muscle that we will see in our little tour of the. So spinal nerve root levels are C8. OK. So very important addition to helping overall grip strength, power grip with superficialis. It's the weaker of the two, but it's not a weakling. It's actually a lot of people go o[. It must be, you know, when you look at it and the cadaver lab is, is it kind of wimpy? No, it's really not. It's just deep. It's unique looking because when you do transact and remove and retract or at least retract away superficialis. It's very much, it's very interesting. It's got this deep white fascia that feels like. Almost like glass. So it's a fascial plane because superficialis and profundus rub on each other when they contract. So you want low friction, you don't want fasciitis. And it's a beautiful looking piece of tissue and you see it by. Flexor pollicis longus. So flexor of the thumb is the longest. You must be aware of this, right? And there it is. And all this guy does, you know, you got one job, 2 Bob, and all you gotta do is flexible foam, right? And there it is. You can see it's going around, it's got a good pivot point going through the carpal tunnel and coming out here to flex the thumb. Is this your supply? I'm going to ask you nervous. I'm going to ask you, sorry, I said nerve root. I'm going to ask you peripheral nerves on our quiz. Well, our final exam, this material will be on it. I'm going to ask the innovation and actions more than anything else. Don't go memorize every little word. So mostly nerve supply and some actions. All right, Pronator Quadratus, there he is. So you see in the illustration, sometimes it's nice to look at artist renderings of what we think it looks like and then what it really looks like. So you can see it's a very much horizontally oriented perpendicular to the bones into the joints muscle. So when this muscle contracts. Physically contracts what's gonna happen between the radius and the ulna what do you think is going to happen you think you're going to be able to squeeze that you're going to bring together the radius and the only not a chance look at that tough interosseous membrane in here and that's actually the anterior interosseous nerve right there which terminates as it's. Quadratus. It terminates underneath it. It does not go through the carpal tunnel. So when this muscle contracts, it makes the radius and the only roll and this is called pronation and this is the power pronator. Like I was putting hooks up in my garage not long ago and. Drywall, but I had these rubber coated hooks like for bicycles, helmets, kayak, whatever. And you know, pretty, pretty big hub, you know. Couldn't overcome it explanation. So I couldn't get through that. But that coronation, that's just muscle. That's the power pronator, pronator quadratus. So there's some more pictures of the brachial plexus, and in this case it's terminal branch called the median nerve from the Netter Atlas. You can see what I love about the Netter Atlas. It wasn't always so scaled drawing to scale, but he tells the story in one play so you know. You can see the sensory distribution, the receptive field. In other words, when I touched my skin here, that's the median nerve picking that up when you go look on the door, some in the fingertips with tips of digits index middle and a portion as you would expect of the ring beautiful and then. And of course, we're at the median nerve derived from the brachial plexus. It is derived from. Coming together. Organizational summary chart of the forearm and this is the anterior surface in the posterior surface of the radius and the owner, and that's the interosseous membrane. So the median nerve innervates what superficial muscle, more superficial muscles in the anterior interosseous. Those deep muscles of the flexor compartment. Now let's take a look at the posterior forearm and the posterior forum. This makes sense, doesn't make total sense. It's radial nerve no for triceps elbow extension, and it has a deep branch called posterior interrupt. It has a deep breath called Deep Breath. You know the anterior compartment is largely flexors and pronators. Well, the back of the arm and the forearm in this case is extension and supination as its main job. Extension and supination. I think we've gone past our normal break. So let's take a quick 10 minute break. We'll come back and talk about the pressure compartment and finish up this last year. See you soon. We were going to just transition into the posterior compartment. So the anterior compartment is flexors and pronators for the most part. The posterior compartment of the forearm is comprised of extensor and supinator muscles and it's mostly under the master control, if you will. The radial nerve, whereas median nerve is the master controller of the flexor compartment. So if we look at the posterior compartment, we're going to break it down in the very same way. It's not quite as clear cut, superficial and deep, but but it is a range in a similar fashion. So if we look at the superficial layer, we've got a bunch of muscles here. The Antonia is the brachioradialis, extensor carpi, radialis longus, and brevis. Extensor digitorum. And extensor carpi. We'll come back to these now. You notice they're in colors too. Take a guess on what you think the yellow is. And it is radial nerve, radial nerve proper. The blue is the deep branch of the radial nerve. Now these all popped in here while I was showing the nerve. And of course the CD player, much like the deep layer of the flexor compartment has the pronator quadratus this has. The main supinator muscle of our four. It's a very, very deep muscle. Radial nerve. The radial nerve traverses out distally, innervates extensor carpi radialis brevis and these are actually deeper to the longest. That's why it picks up some fibers from from the deep branch and then it deep in your base, the supinator and then that nerve. Literally comes out the most muscles are innervated from the low. By the way, the other kind of seeing that or got that idea from these illustrations and it innervates the supinator from below, but as it continues out past the border, it pops up and it forks like a wishbone. OK. And we call that nerve now the posterior interosseous branch of the radial nerve. It's actually according to the anatomical nomenclature system, it's its own nerve called posterior interosseous nerve. Like the anterior interosseous nerve is not the median nerve. It's its own nerve. It's a branch derived from the median. And this is a branch derived from the radio and. Everything in white, you see is innervated by that nerve. So if you look at all of these extensors extensors of the digits extensors of digiti mini me like doctor evil will abort a mini member that or extensor carpi ulnaris, extensor pollicis, extensor pollis brother belongs extensive. They're all posted in the o[ice. So really the majority of muscles called extensions if you're gassing without secure against her department, not memorizing things so much you're trying to learn it, but that's what the interactive. So we'll go through a few of them here and you can see the brachioradialis muscles being here and the breaking. Yeah. So I always call it like it's, it's the same. Yeah, like out West with the cow fence between properties and ranches. It is, it is the flexor and extensor compartment center. So the brachioradialis originate on the upper 2/3 of the lateral supracondylar Ridge, the condyle. Humorous and it originates from the point here is that originate from the humerus crosses the elbow. So what does it do? It flexes the elbow so it flexes a semi prone elbow. So instead of you going to the gym. You go and you do curls with about one barbell like this. You're largely using your biceps brachii. You take a dumbbell. And you grip it vertically like this. You're using this muscle, you're using your biceps, but this flexes the elbow joint in the semi prone, so-called semi prone or some people say semi 2 simulated position and that's what it does and it's radial nerve innervated, it's mostly sees it. Sensor carpi radialis longus and brevis. They're long guy and the short guy and have two di[erent innovations. Sensor carpi radialis longus. It's action is to extend the risk as you would imagine and it also has some cocontraction discredited and this is ready on their proper with final level C6 and C7. Now when we look at extensor carpi radialis brevis. A little shorter brother. What's the trick? It's the deep branch of the radial nerve and it's mostly C7, so deep branch of the radial nerve. And what does it do? It helps out. It is this extensive. So I guess you can figure that out next question, right? Sometimes anatomy makes total sense and sometimes it comes out with you guys and I can get you seen so far which counts. So the origins, the lateral epicondyle, the humorous and extensive attendance and. Enter. Called EDC extensor digitorum communis so if you see it as EDC that C is communist what does that mean it means common and it has a common origin and you see up there it says via a common extensor tendon so when people have. You go out and you do things like I know I was using an electric hedge trimmer not long ago and this spring and I'm using my right hand dominant, I'm holding this thing in extension and it's not something I do a lot of before delayed onset muscle soreness keeps out like 48 hours, two days later it was really tender at that and that's called. That's called lateral epicondylitis. Used to be called tennis elbow but that's when tennis rackets were made of wood and you didn't get that didn't hit the ball in the sweet spot. I know I had plenty of non sweet spots with the Jack Kramer Wilson wooden racket as a teenager. You get epicondylitis and then the advent of metal and graphite, carbon fiber, Kevlar. These are all smooth rackets and you don't see that as much metal. This is sometimes referred to as golfers elbow. We don't see that either because the materials have changed too. You don't hit the sweet spot on the golf ball with a steel shaft club. You get a big Zing don't you up your arm. So things have changed. So this is a common extensor tendon. And of course. This is a major extensor of the metacarpophalangeal and the interphalangeal joints, very, very powerful muscle relatively speaking, and it is all contained by a retinacular. Now retinaculum. We mentioned the the flexor retinaculum. This is called the extensor retinaculum. It is a very tough connective tissue band that keeps these tendons in their tracks. And there's a, there's a bump on the radius called Lister's tubercle. And these, these tendons go, one of them goes right through the cues for bone grass. I've had one done. Sensor carpal naris. What does that do? It extends the wrist and it's on the ulnar side. Simple enough. Who innervates it? Don't be fooled you say? Ohh wait, this is all NAR. Not a chance. It's innervated by the deep, more deep branch of the radial nerve called the posterior interosseous nerve. Try not to read all these. Here you go. You can go back to yourself. I'm hoping if you haven't seen most of my lectures kind of are in a textbook kind of format themselves. I use other materials to deliver a lecture and I I think is is a. Educator, if I'm using this and you don't need to go read 40 other books, you can, you can use my Alice that I use pictures from and I use, I mean, you can see these are from common textbooks, but it's correlated for you, so you don't have to go run around looking for it. And that's how I do quizzes and tests. Abductor pollicis longus. Abductor Paulus. As long as is very unique, it actually crosses over the bone and we don't really see that in anatomy of too much. When muscles crossover bone and it creates friction and it can put that normal undue stresses on joints. Even so we don't see that very much, but it crosses over because it AB ducks that sun AB ducks with them away from the midline and it's supposed to your interosseous nerve as well and it AB. Extends the thought you need to need to ride home. That will help you out. Extensor pollicis brevis is an extensor of the thumb and it's in the posterior compartment relatively deep and it's posterior interosseous nerve CA and it extends the metacarpophalangeal joint of that since her policy as long as extensor policy as long as you see here in the blue. Becomes way across from the Old Norse side of the posterior interosseous membrane. Comes across a pretty sharp angle under the extensor retinaculum. Has a pretty good amount of power on the extensor aspect of the thumb, and it extends the thumb and the interphalangeal and metacarpophalangeal joints of the thumb. You get the picture. The extensor compartment, the posterior posterior arm is radial, extensor compartment of the forearm is radial, deep radial or what else? Posterior interosseous. And the posterior interosseous nerve I think is 16 muscles or something. It's the majority of 16 muscles. And then I think lastly, maybe not lastly, but I think it is extensor indices, meaning index. Di[erent compared to the flexors like Texas Longhorn, we have index and minimum. So we have extensor digiti minimi, which is next coming up, but extensor indices. What's unique about this is clinically it's used a lot. I use it when I do a radial nerve motor nerve conduction study on a patient. Because it is. You see it going here to the index finger. Now, extensor digitorum communis or extensor digitorum, yes, it extends all four digits, not the thumb, all four digits, but this muscle is separate and unique in addition to that acting on the index finger and it's the most. This school in distally innervated radial, if you will, obviously as opposed to interosseous nerve, but it's still considered regular. It's the most distal innervated radial nerve. And in electrodiagnosis we test the most distal nerve that we can. We test the whole segment of nerve and that's as far as we go. You notice there's no muscle bellies. No muscle tissue innervated by the radial nerve or any of its branches intrinsically within the hand. There's muscles that act on the hand, and clearly this is 1, and several obviously are, but it's not intrinsic to the hand. What is intrinsic moth with the intrinsic muscles of the hand? They're innervated by two nerves, median and mostly what? OK, so extensor indices. What does it do? It is causing extension of the index finger assisting extensor digitorum. I find it. I palpate the ulnar styloid. I have the patient move their finger like this at the interphalangeal joint I palpate. Two fingers breathed from the ulnar styloid 1 medial. And that's the ability of the muscle that you see right about where that feels like a little tiny. It's a tiny little muscle. So let's talk about the carpal tunnel. It's probably pretty much our last bit of information for the salient features of the upper limb. And of course a lot of this is neuromuscular because that's what goes wrong. We're not, we're not an orthopedics program. We're in neurology program in neuroscience. And this is a really nice illustration of the flexor retinaculum. So this tendon that you see here. This is Paul Myers longest and that's the. That's the retinaculum. So we cut that away and this is called. This what you see surrounding it and it's underneath it, this fan shaped thing is the retina is the Palmer's longest. This is the flexor retinaculum. It's the roof of the carpal tunnel. That's what you see right here. So carpal, carpal bones make up the wrist. We have two rows, there's eight of them. There's a distal carpal row which has this sca[old and the lunate and the piezo form. And this carpal tunnel is made-up basically on three sides, if you will, by the these carpal bones. So the median nerve goes through there. And the median nerve is you can solve this. It's amazing in the state of health how jam packed this is. It's about that big. I mean, it's, it's smaller than your than your small finger with the power these flexor tendons going through, a lot of those tendons are going through the roof. You can see the forward and so forth. So in the palm, what we do is we divide the hand into the thenar eminence, thenar muscles, the hypothenar, which is this side, the Ulmer side, and then we have a so-called central group. And if you do it this way, it's pretty easy to actually even memorize. So the thenar muscles are innervated, and they're di[erent colors. They're innervated by the median nerve. All right, after it goes through the carpal tunnel and call it the recurrent median nerve because it kind of turns around and goes back to the thenar eminence. And these are the abductor pollicis brevis, flexor pollicis brevis and the opponent which this is opposition, you'll notice there's an opponents here. So think of it this way. There's abduction, flexion and opponents. Those are the actions of these hand muscles, these intrinsic hand muscles. There's one on the thenar side and there's one on the hypothenar. What's the di[erence? What's the dominant feature over here? Did you team enemy? What's the dominant feature over here? The thumb. So it's really simple, Abductor, flexor and opponents of the thumb. Abductor, flexor and opponents of digiti minimi. What are these all our innovative what are these media simple. Now here's the trickier part. If it's that and that is. The so-called central group, we have a muscle called AD doctor. Lot of people screw this up back. National boards and medicine, chiropractic, Podiatry, dentistry. I'm fairly familiar with all of them. They always put this in there. I've been on a couple of those boards and it's a trick point, right? Let's do this. That will trick them. I never really understood that. I mean, I like questions that test the depth and breadth and somebody knows about tricking them. But adductor means I'm bringing the thumb towards the midline. So it's not AB duction, it's adapter and it's a very, very deep muscle. It's innervated by the owner nerve. There are 4 lumber coal muscles and. 4 Dorsal interossei and three palmar interossei. Dorsal interossei means between bones on the dorsum. Palmar interossei mean between bones on the Palmer side. They're deep, but they're in the Palmer side. All muscles. Very, very important here. All muscles in the palm are innervated. All muscles in the hand, let's say hand even, are innervated by the deep branch of the median nerve. Except for the medians, right? So let's rephrase that. Make sure I got it correct, because I think I screwed that up. All muscles in the palm are innervated by the deep branch of the nerve. Except for the thenar eminence and the first two lumbricals which are median and all of them have spinal levels. Look at that. Beautiful. Action pack a[ect keep your work. All have spinal nerve root level CT when the hand is easy. I remember in school everybody was like ohh the hand is so complicated there's 18 muscles. I'm like are you kidding me? They have the same prefixes in the same su[ixes. Abduct. Flexor and opponents. Abductor and Flexor and opponents. And then you got these little weird lumber calls. They're just little cry look like miniature little chicken strips. They're just like these little stabilizer muscles. These two are median. These two are Omar. That makes sense. And then. These guys, they, they're deep hand muscles. So they're all are innovative. Let's take a look at that. So there is abductor pollicis brevis. It's just the meat of your thenar eminence right here. And you can see that it's innervated by the median nerve. We call it the recurrent. Branch of the median nerve, because it it goes through the carpal tunnel back, it's going to run right here next to the tendon of flexor carpi radialis underneath the flexor retinaculum. And it's actually going to come back around and then be underneath what you see there for #2 therefore it's called the recurrent branch recurrent. By way of recurrent arteries, they go past something and they come back. That's just an anatomical term and you can kind of see it turning back here. And it reduces the thought. And I love it when stu[ makes sense because it doesn't always does it, even in neuroscience. I say even in neuroscience, I'm so biased, but it doesn't always make sense by terminology alone. Abductor, digiti minimi, what does he do? Boom, she does same thing. It is a deduction. Now remember when we talk about the midline humans, we say this is AB duction, this is AD duction adding. But when you get to the extremities, the hands and the feet. We used the palmar region and the anatomical position, which is this, right? My shoulder won't move that far. So this is a reduction of these two. That's a reduction of those. So the midline here isn't that weird. It's di[erent than the truncal or larger muscles. Know your AB docking, you're taking this digit team enemy the 5th digit and you're taking it away from the midline and it is fairly lateral. We use this for our ulnar nerve motor study recording site. We do nerve conduction studies and we also use put needle EMG electrode in it when we do elect EMG on that muscle. Abductor, Digiti, Enemy and there you can see it as well. Deep branch of the owner nerve, Nerve roots for the hand muscles or what? No memorization, they're all CAD. One beautiful stu[. So it abducts the little fingers. Dorsal interossei. So on the back of the hand you have interossei, meaning between bones. There they are. And you see how deep and look at everything's gone. I mean, these are deep muscles and it's innervated by what? Innervated by the deep breath of the owner nerve. CAT1. So we say 4 dab and then we also say 3 pad. What's that mean? 4 Dorsal interossei I. And they do what? They abduct. Do this. And then we have 3 pad, 3 Palmer. And what do they do AD they add up? They're the antagonistic muscle. Simple. Remember 4 dad? Then you can say 4 dad, 3 pat. What's the trick? There isn't a trick. They're both both these sets of muscles are all in our innovative. So just kind of a primer or an overview, if you will, of the upper limb starting at the nerve root levels C567 and T1, forming the famous brachial plexus and going out to the three major. Branches, the median, Omar and radial nerves, obviously they have subdivisions and branches for deeper compartments and specialized functions in the forearm. And also these intrinsic hand muscles are somewhat unique as well. So go back and review those what we're going to do in the second-half or the second part of this week, finish up. We're going to take a look at the lower extremities and as I said, it's a little easier. You know, it goes by compartment, same nerve, blood vessel, even nerve roots really for all the compartments. So it's much easier and a little bit less, less number of structures. So it's quicker. And then lastly, we'll do a brief intro to the autonomic nervous system to get us in order because you'll have a class. Anomic nervous system in the future. So appreciate your attention. Have a good rest of the week and I'll see you a little bit later on. We'll talk about the lower, lower limb as well. Have a great day. Lecture 2 Welcome to our second lecture for our last week and you know you are 5401 Advanced Functional Neuroanatomy. So this is lecture 2 or mod 2 and this lecture is a introduction or an overview, a cursory overview of the anatomy of the lower limb, the neuromuscular anatomy. Obviously in the in the field of neuroscience, we're not as much concentrated on on joints and ligaments and tendons and so forth. We're more involved with muscles and innervation. I think you would understand. So let's continue on with this and then what we'll do is one more lecture introducing you to another aspect of the. Peripheral nervous system called the autonomic nervous system. So the lumbosacral plexus is analogous to the brachial plexus that we looked at earlier this week in the upper limb. The good news, bad news scenarios and that and that's what it is. The good news is there's really not a highly mobile major joint or a limb nearby that can stretch or damage the brachial plexus, or in this case, the lumbosacral plexus. There is in the brachial plexus the highly mobile, very freely movable glenohumeral joint. North Mobile joint. And certainly it can stretch and cause problems with the break of plexus. We don't see that with the hip joint. You don't see people that can spin their hip joint around. What we do have a problem with is that the lumbosacral plexus arises from the L1 area, the L1 nerve root all the way down. And what this does is it allows for the viscera that's in this abdomen, if you will, then you know mediastinum is up here and then the abdomen is here. It allows for the potential for visceral organs and organ pathology to a[ect these nerves. So when a patient has. Pain and tenderness, say for example, and the inguinal region or in the anterior thigh region that doesn't match a lower nerve root level pattern for disc herniations and typical lower back pain. That's a little bit of a yellow flag for me that I'm going to work up to make sure they don't have visceral problems. So this is called the lumbosacral. Some people call the lumbar plexus, but we call it lumbosacral when we include all the sacral nerve roots and of course it arises from L 12345 S 123 and down in the S123 levels, the sacral nerve root levels, that's down in the perineum. So things like erectile dysfunction is so-called. Is innervated by nerve roots as 234, bladder and bowel function and so forth. The good news is we don't really have disc herniations that a[ect that area too much. It can because remember that the conus medullaris the end of the spinal cord. And an adult. And an adult person. Not a newborn human, but an adult human word is determinate. Conus medullaris terminates at L basically at L1L2. And you say OK, well this is S234, yes, but here's what happens. These sacral fibers come down through the quarter and this carnation is along the way. And in fact. It's not as likely as the L5 S one, but it can a[ect it. So the major nerves that are derived from the lumbosacral plexus are the sciatic nerve and you can see it's it's depicted here where my my cursor is moving around. Into a medial division which is yellow and a lateral division which is orange. So the medial division is the sciatic nerve. That's tibial division and then the lateral part of that division is the so-called fibular or it used to be called peroneal division. And we see that in terminology these days where we used to call these things like. Deep peroneal nerve, superficial peroneal nerve, they're now called, and we'll get to that in just a few moments. You also see things like the obturator nerve here, and the obturator nerve is very rarely injured because it's very medial, very well protected by the adductor muscles as well. So not a whole lot of problems. Another nerve here that's very large that comes underneath this so-called inguinal ligament is the femoral nerve. Now the femoral nerve innervates the quadriceps muscles. Quadricep muscles or the vastus medialis. Vastus lateralis. And we also see rectus femoris and vastus medialis. And so these are the thigh muscles, if you will, and these are knee extensors. Very rarely do we ever see a femoral nerve lesion. I haven't done a femoral nerve nerve conduction study in five years, maybe more. And I do nerve conduction studies immediately in every week. It's just not a a nerve that has a lot of lesions just by based on the location and and it's it's passageway which is very safe and not very tight underneath this angle. OK, so just an overview of this lumbosacral plexus. Take a look at it and get a sense for where these nerves arise and where they pass through. Now first thing we're going to talk about are the upper lumbar nerves that are mostly sensory. They're not as exclusively sensory, but the vast majority are sensory and they arise. On the old 1234 levels which this carnations do not occur very often in the upper lumbar spine. So when we have problems with these nerves, a little bit of a red flag if not a yellow flag maybe because look what we have here. We have all this viscera, we have the abdominal aorta, we have the vena cava. The kidneys. With these kidneys, with the adrenal glands up on the superior poles. And what's been removed in this illustration is the adnexa and the female, the uterus, the ovaries, the fallopian tubes. And of course the most of the GI tract has been removed in this illustration as well, and the bladder. So just to give you an idea of where these nerves are, they're related to a lot of structures. So for instance, if somebody has has been in a car accident and this happens a lot where I'm at, there's a lot of construction going on on the Interstate. You guys in the Dallas. Or were there, you know, all about this, it's a major growing Sunbelt city. So you'll see somebody sitting still in heavy tra[ic, probably texting, doing whatever and doing a phone call. And I had, I had actually had a patient a few weeks ago who said she was sitting in tra[ic. Testing. That stopped and she had been stopped for a couple of minutes and a man hit her from behind. She was in a Mercedes E Class 4 door sedan. It's a mid size car. He was in a Ford F-150 full size pickup and he admitted because the speed limit was 70 before the construction zone, he admitted he was on cruise. Control. And was texting and he looked up as he hit her. He did not even hit the brakes. This is a major impact. This car was destroyed. And those are those that model cars are pretty solid vehicle. It was destroyed. The seat, the seat itself was broken on the bracket and she had tremendous whiplash e[ect. She has a traumatic brain injury. He's got brachial plexus stretch and that makes sense based on the three-point belt harness. We talked a little bit about that earlier this week that it gives a kind of a pivot e[ect kind of a stretch on the brachial plexus. This isn't the case down here in the lumbosacral plexes, but there's just no kind of. There, there. There's not any way to get leverage with a limb on it. But when we do see people having problems, we have to be thinking maybe there's something going wrong in the viscera and the organs in this region, and it's very prudent for us to do so. And you can see the vena cava and the abdominal aorta. And of course the kidneys and the common iliac arteries here as well. By the way, abdominal aortic aneurysms are very common. It's an older man's disease more than his female. And these abdominal aortic aneurysms, we call them AAA, they can rupture and there's no surviving that. OK, so. That's something to consider as well. So if we look at. These major muscles, we look at some that many of you know about quadratus lumborum, quadratus lumborum, the SOAS major and minor muscles in the iliacus. These muscles are involved in back pain. A lot of people talk about how these muscles have a lot of tension on them producing back pain and when we stretch. Side posture when we roll their pelvis over we stretch these muscles especially SQL and so as so as is stretched by having a patient Lisa Pine or on their back and bringing their hands up to their head and stretching them out and many times this gives people relief from back pain just from those stretches now. Here's what I'm talking about when I talk about these nerves that are in the retroperitoneal space or the posterior abdominal wall. And again, this illustration has a lot of the viscera even more further removed than our previous illustration, but I just wanted to get an appreciation for this. This is the abdominal wall. This is the retroperitoneal space. And so these nerves that you see here are labeled are literally lying on that back wall. So this is called the subcostal nerve, which means below ribs and that just innervates skin and kind of around that region. And I'm going to show you a illustration in a moment where. This so-called receptive field in in other words where on your skin if I touched you with the pinwheel, this subcostal nerve would be transmitting that information and then iliohypogastric ilium and then below stomach you can see it coming out here and going around laterally ilioinguinal. Comes out by the ilium goes out and it actually goes through the inguinal ring and the inguinal ligament and innervates. Some of our inguinal region or genitofemoral actually pierces the belly of the so as muscle and genitofemoral is supplies sensory modalities just what it sounds like. Lateral part of the genitals and into the femur region or into the thigh region. This is not sexual function or sexual sensations. That's the pudendal nerve, that's sacral nerve and that's that's 234. This is just simply touch. So like labium and females and scrotum in males. Verify. Obturator nerve obturator nerve is running down here underneath the inguinal ligament and provides sensory innervation to our AD doctor. Muscles are medial thigh muscles. And of course one last and actually it's fairly well known the lateral femoral cutaneous nerve comes out here laterally and it comes underneath it takes. Actually kind of a tortuous 90° turn underneath the inguinal ligament and innervates the lateral thigh. And then lastly there are really big nerve on the anterior aspect. Of the pelvis is the femoral nerve, which of course innervates the quadriceps muscles and provides some sensory innervation. So muscles in the posterior abdominal wall, we can see these muscles that I just mentioned, the iliohypogastric, ilioinguinal and genitofemoral. And again, I'm not going to. You've got these notes, that's why I give them to you. You can read through this. I want to show you again, this picture is actually very salient because. It shows us the looks are it shows us the location of these nerves and where what we call in sensory neuroscience, we call this the receptive field. In other words, if I run a pinwheel up your lateral thigh, that's the receiving or the receptive field of skin or dermis for that nerve. So you can see the subcostal nerve is a very little tiny, very small patch just under the hip. So your ribs are kind of can't make my cursor go up higher than that. It's just out loudly to rib margin. And then the lateral femoral cutaneous nerve you see here is in the lateral femoral genitofemoral. That's makes sense that it's somewhat. And this patch of skin here ilioinguinal supplies of very medial part of the inguinal region. And again as I said, the scrotum in males and labrum and females, many people, many men especially who have inguinal hernia repair which is the most common general surgery operation in the United States most. At the time they sacrificed this ilio inguinal owner and people complain about abnormal sensation in this region. I've had plenty of patients tell me they've had that done and they just don't really have a whole lot of feeling there. And then lastly here the obturator nerve, even though it innervates the the thigh adductors. It still has a sensory patch if you will, just here above the knee, the obturator nerve. So as we go to the posterior aspect of the thigh and the leg, we dissect away the glue, the gluteus maximus and the medius and the minimus here. And you can see a muscle called the piriformis muscle right here. And the piriformis muscle runs from the sacrum. Out towards the femur and when it contracts it's an external rotator of the femur when it's when you're weight bearing is a stabilizer of the pelvis. But it's fairly famous because this famous sciatic nerve passes underneath it and it can sometimes squeeze that nerve. And of course, the sciatic nerve as it travels down the posterior thigh, about 2/3 of the way down before the so-called popliteal fossa behind the knee, it branches and it branches into a common fibular nerve and then a tibial nerve opposed to your tibial nerve. And there's just some of this sensory nerves over here on the left and providing some sensation to the skin. So again, here's the sciatic nerve and you see it in yellow and green. And the yellow division is the lateral division, that's the so-called tibial division, excuse me, so-called fibular division. And the green is a tibial division. We'll get to that in just a moment. OK, so all these nerves are branches of that. It's a fairly complex plexus of nerves. Now here's where we we should, we should stop for a minute and take a chat. So there's the piriformis muscle as I said, and you can see it runs from medial to lateral. So if it were to contract. It would rotate this this femoral head. External rotation or outward direction, but when you're standing and weight bearing, both of them contract and they're pelvic stabilizers. So you can see a bunch of nerves coming out of here. And of course the the gluteal nerves, it makes sense that they supply the gluteal muscles and superior gluteal nerve supplies. Gluteus minimus and. And the inferior gluteal nerve supplies the glute Max, gluteus maximus, the largest of those muscles. So we have a a strap like a set of muscles that you can see here. Let's say that we have, you know, the femoral heads coming down here and we're going to have the piriformis. Here that you see here going to the femur and then we have another muscle here. And this is the superior gemellus. And then we have the obturator internus and this appear in the inferior gemellus. So superior gemellus, obturator internus and inferior gemellus. And so the sciatic nerve comes out underneath the piriformis. Is actually running over the top of these three muscles. So this can be a side of tension or problems in this static nerve for many patients. So we we want to know how to stretch these and, and therapeutically they're just external rotators. So we stretch them in that, in that direction. And so that's the the nerve supply and those are the muscles. So superior Gemellus. And then the obturator internus is the meat between them. This, if you want to view it that way, is the sandwich. OK, so let's chat about these named peripheral lower extremity nerves. And we we mentioned these very, very deep retroperitoneal abdominal nerves like the subcostal iliohypogastric, ilioinguinal, genitofemoral, obturator, lateral femoral. We named all these, let's take a look at them. So if you look at these upper so-called upper lumbar superficial nerves, these are mostly sensory. And again this is reviewed from what we just looked at the subcostal mirror below the ribs supplies are very, very small area of receptive field. Then we see the iliohypogastric nerve pierces out of the sodas and comes down and it supplies an area of skin kind of above the pubis below the stomach area. So ilium and then hypo below stomach. That makes sense and then. Again pierces the muscle, the so as muscle and it is supplying us nearest skin halfway between the genitals and the femoral head. So it makes sense to me. Genital, femoral and then ilioinguinal comes around the ilium wraps and comes around you. Don't really see it here in the illustration, but it comes around through the actual inguinal ring, comes through the inguinal ligament through the ring and provide some sensory innervation to the very very medial thigh and portions of the gentiles. As we mentioned, lateral femoral cutaneous nerve is. Lateral branch. Sensory nerve and this lateral femoral cutaneous nerve comes out and takes quite a tortuous 90° turn this way underneath the engine ligament to innovate the thigh. So tough nerve study. You can't do these nerve conduction wise or too deep. You can do this. Do you want some? While somebody will ask me to do it and I don't wanna do it because it's very, very challenging even on the most thin people. And then the next thing is, let's say this person does have this, this region that has pain. And I tell you, that nerve looks like it's being compromised. What are you going to do? Is it surgically innervated or intervened? You could potentially have them stretch, maybe stretch and try and do some conservative things, but there's just not a lot to do for it. There's the obturator nerve again, and that's just a very small area of skin for sensory modalities on the medial thigh above the knee. So there's the sciatic nerve again, and the tibial nerve. What's the branch laterally o[ the sciatic tibial division? It's called the common fibular nerve. We already looked at that, so let's finish up by just taking a look at the schematic for these nerves and then we'll move on. So there's the piriformis muscle, and you can see the superior gluteal nerve going up to the glute medius and minimus, and then the inferior gluteal nerve is down here for gluteus maximus. Now people say, you know, it seems like it would be the other way around because the glute Max is so big. It is, but it's actually a little bit lower. So think it's a little lower than glute medius or minimus. Ross roll Cottle copper bottle. So inferior gluteal nerve makes sense. So the sciatic nerve traverses down by the posterior thigh and it innervates ultimately these hamstring muscles, as we call them, the semitendinosus and semimembranosus, the medial hamstrings. And then we have the two lateral hamstrings, the long and short head of the biceps. And the short head has innervation from the common fibular nerve. So common fibular nerve, fibular division sciatic has L5 in it. And fibular division. And so that's the only muscle proximal to the knee that has that, and that's the short head of the biceps. And then of course, the tibial nerve itself crosses through the popliteal fossa and innovates the medial and lateral heads of the gastroc, soleus and of course the deeper muscles and tibialis. And flexor digitorum models and flex your house. So the tibial nerve then continues on. Some people call it in Europe and see it in Canada too. They call it PT it close to your tibial nerve. Most folks here in United States called the tibial nerve. But as it passes through the famous tarsal tunnel. And it has a flexor rat in it, flexor rat neck retinaculum over it just like the carpal tunnel does in the upper limb. And that tibial nerve passes through that region to the foot and right at the tarsal tunnel and right at the flexor retinaculum it branches into how you doing the lateral. OK, So what about the lower leg? If you look at the lower leg, you can see the fibular head and neck right here on the lateral view. And so the the tibial, the tibial nerve, so the sciatic nerve, let's draw that out. So the sciatic nerve is coming down here and the right before the knee and let's draw. That's really what the popliteal fossa is like that So the sciatic nerve comes down and right before this region it shows o[ a branch over the cloud and this is common. Peroneal. Common peroneal nerve. Common fibular nerve, that's what I prefer. That's the newer terminology, common fit. And then this just continues on this branch of the sciatic nerve continues on as the tibial nerve. Still not the gold standard. Nerve. Then goes out laterally and branches. Superficial. Fibular. So it's very simple. This lateral compartment that you see here with this big tendon on it, those are the peroneus. Well, guess what else we call them now and the new terminology regulator. These are peroneus longus and brevis or fibularis, longest and brevis, and they're innervated by the superficial. Goes around anteriorly. They both. You can see it here. It passes around the fibular head, neck, superficial space, lateral, and the deep goes exactly what it's called. It goes deep and goes in, goes distal anterior, and this applies all the interior leg compartment muscles with so-called dorsiflexors of the foot. Seems like tibialis. For longer. Now, I told you in our first lecture earlier this week. When we do the upper room, I said, look, it's a little easier in the lower wind because each compartment only has one nerve. And I haven't really visited that concept which yet with you today in this lecture. But let's start now and talk about that because we have compartments. So for instance. The lateral compartment has one note. Superficial. Thank you. So superficial fibular nerve compartment peroneus or fibularis longest ever. Go up And. What's the nerve? What's the blood supply? Fibular, fibular, simple. So let's go to the anterior compartment. Deep fibular nerve and there is an artery called the anterior tibial artery. Simple. Anything in the anterior compartment, any muscle in the anterior compartment. Let's take a look at them. They're all intubated and. When they receive their blood supply and respected by their structure. So the common peroneal nerve is what superficial peroneal and you can see the deep goes interior innervates tibialis anterior extensor digitorum longus and extensor hallucis longus. Now they there's also peronia Perseus and extensor digitorum brevis from the deep. Now in the superficial or the lateral compartment, sorry, the superficial nerve innervating the lateral compartment, probably as long as some breakfast. So I can have a very simple schema. So there's the tibial nerve passing through the popliteal fossa and you can see it's underneath the gastroc and soleus. The gas truck and solius and it as it goes into the foot, which it's ultimately going to do, you can see it traverses somewhat medially, very slowly. It goes underneath the flexor retinaculum through the so-called tarsal tunnel. And there's not a lot of problem with this. There's plenty of room here. It's not nearly as tight as the carpal tunnel. Could I have podiatrist? Ohh, I'd say monthly I get a Podiatry referral to say hey, do electrodiagnosis on this person because I think they have tarsal tunnel syndrome. And I never, not never, but hardly ever have abnormal nerve conduction studies. But these people have foot so there's something. But it doesn't seem to be very electrophysiological. Lastly, I want to just kind of finish our our our little intro discussion this week in the lower limb by telling you about the famous sural nerve. Sural means cast. So you may have heard that term tricep Surrey, tricep Surrey reflex. The tricep Surrey is the triceps of your calf, then that means the medial and lateral. And so some people call this circle, some people call the Phillies, some people call it triceps. So that's where the word comes from. So you're saying, what does that mean? Well, here's what's happening. This nerve is the most distal. You can see it right here. Disco. The old pumper heart. So remember when we talk about things like diabetic polyneuropathy, these are linked dependent polyneuropathies. Less blood flow. So this serial nerve is what we call the electrodiagnostic version of the biopsy. So in other words, if you say, hey, you know, my mom has diabetes, type 2 adult onset. She was diagnosed 10 years ago with it. She's kicking, numbness and painful tingling in her legs and feet. Would you do it? Diagnostics. Because it is the most distal sensory nerve axons that we can readily test and it's it's positive if you want to call it that and everything from diabetic polyneuropathy to lines and lines disease. And so very, very common task and we'll talk some more about that. We're going to talk about all this stu[ and more, much more in depth and a lot of cool diagnostics in the peripheral nervous system course. So thank you for your attention. We've covered upper limb intro, lower limb intro and the last thing we have to do this week is come back and introduce you to the autonomic nervous system and then our. Our job is done in this course and I'll see you a little bit later this week. Have a great day. Why not? What about the parade yesterday? What about it? 1. I know that. What's happening today? You know, so this girl at the end of the party, she called these two guys and they and they sounded a lot older than us. And then they were showing like she was like showing the rest of the people. Yeah. It's Tuesday. Why? Don't do that. What's happening on Tuesday? Can you ask her? Ask her what's happening. No, while it's hot. You have to drink it while it's hot. Is that what you were talking? That what you were talking about?