Lumbar Sacral Plexus & Reflexes PDF

All right, our third recording is going to cover the lumbar sacral plexus plus some clinical context in terms of reflexes, right? So the lumbar sacral plexus is really the combination of lumbar and sacral plexus, right? Pretty straightforward. That's going to go from L1 down to S4, okay? So just mak...

All right, our third recording is going to cover the lumbar sacral plexus plus some clinical context in terms of reflexes, right? So the lumbar sacral plexus is really the combination of lumbar and sacral plexus, right? Pretty straightforward. That's going to go from L1 down to S4, okay? So just make note that this is the whole thing and we're also going to kind of talk about them individually as well but they do mix here in that lumbar area here, the lower lumbar, excuse me. So it's going to be located in the posterior abdominal wall. So what we would have to do is take out all the GI tract here, all the reproductive organs, the urinary bladder. We would take out the perineum, this lining, that cavity here, that connective tissue that aligns where all our organs are and then we'll finally see muscles making up the posterior abdominal wall. All right, so lots of stuff in front of this. They are divided into an anterior and posterior division. We're going to cover the anterior division. It's primarily the lumbar plexus and the posterior division is primarily the sacral plexus, but there is some overlap here. So keep that in mind. All right, so here is our lumbar plexus. Our lumbar plexus is going to provide innervation, a sensory motor innervation, to the inferior abdomen, and then also the pelvic structures as well. We also are going to send some sensory motor innervation to the lower limb, specifically the thigh here. So we also want to think about this anterior division is providing innervation to the front. Well, because the femoral nerve is actually going to come from this. All right, so if we go from superior to inferior here, we're going to see structures that aren't going to be named for what they supply, right? So this nerve right here, the spinal nerve is L1, is going to come out and it's going to divide here. The superior one is going to be the ileo hypogastric, hypo above the stomach really. So it's going to be the hypogastric region here. And then the ileo inguinal, inguinal is going to refer to pelvic stuff here. So near the ileum, stomach, near the ileum, inguinal. Okay, the next one down is going to be our lateral femoral cutaneous. I bet you can't guess what this one does. So primarily it's going to bring in sensory information from the lateral aspect of the thigh. So there we go. It's going to actually slip underneath this structure here. It's going to be our inguinal ligament, which we'll talk a lot about when we get to the reproductive system here. Okay, for the next one, I'm actually going to jump over here. So this is our psoas muscle. Coming out of the muscle, the psoas, so kind of unique in terms of what we see other nerves doing, is going to be our genitofemoral nerve. Our genitofemoral nerve is going to send a branch to the femur. It's not the femoral nerves, it's the branch of the genitofemoral nerve. And then we're going to have a genital branch. This is going to go through what we'll call the inguinal canal and go to innervate external genitalia. All right, so moving on from those two here. So here's our genitofemoral branch, genitofemoral and femoral, oh, femoral and genital here. Going more medially here. I guess maybe we'll go laterally here. Coming out on the other side of the psoas here, making its way down. It's going to be our femoral nerve. Femoral nerve is going to go on to do basically all anterior thigh stuff. So big one here. And then our final one here is going to be the obturator nerve. And conveniently, it's going to come on down to the obturator for even where it's actually going to exit and provide innervation to surrounding muscles here. So there we go. We don't have a good donor view of these structures. So that's convenient for you guys. All right, so in terms of what these things innervate, we're really going to focus on the femoral and the obturator. Because again, we're going to go back to those like genitofemoral stuff later on. So you can see, actually, you can see the lateral femoral cutaneous nerve coming on out, and it's going to do this pink area right here, just in case I don't explain that. The rest of this here in blue is going to be innervated by the femoral nerve here, right? So the skin of the really anterior or really lateral portion of the entire lower limb is going to be the femoral nerve, cutaneous branches of that, right? Motor is going to do the anterior thigh. So if we think about motor and our anterior thigh, we know that we have hip flexors where we decrease that angle and knee extensors here, right? And there we go. So then our obturator nerve is going to send motor innervations to our adductor muscles. Our adductor muscles, we want to think of adductor magnus and lungus and so forth. We can see that here. We can see that here. So here's our adductor. Let's see, here's our gracilis. This should be our adductor magnus because it's so big. And let's see, we're going to have our adductor lungus will be here. Here's our adductor brevis, which we haven't learned. And then we also have our obturator externus muscle here and our piriformis is deep there. Anyways, beyond that, it's going to provide innervation to this little part in terms of our sensory, right? So medial thigh muscles, that compartment of the medial thigh, which means lower limb adductors in terms of what they do. All right, moving on to the sacral plexus or more or less that posterior division, right? right? There's again some overlap. It's going to be innervated by that anterior rhema of L1 through S4 here. Well, L1 through S4, all of these, it really should, I mean, so that's going to be the whole almost sacral plexus. So we're going to go to, let's see, L5 to S4 divisions here. We're going to rely on, well, there's a plexus. There's, sorry if I'm making music. There is a, the slide where we have those nerve plexuses defined by which spinal nerves provide them, go by that. Okay, so it's going to provide motor and sensory innervation, right, to the **** region, the gluteal region, the pelvis, the perineum, and the posterior thigh, and then all of the leg. So really this sacral plexus is really big and important for our entire lower limb because it's going to innervate all the muscles outside of that anterior and medial thigh compartment. So motor and sensory innervation, if we look at the five nerves that come off of it here, we're going to have three that come off superficially here and provide innervation really to the gluteal region. So we'll have a superior and inferior gluteal, and then we'll have the nerve to the piriformis muscle come off, and then the rest of, well not the rest, the majority of these spinal nerves are going to come together to form the sciatic nerve, which is really, really big, and it's big because it's going to provide a lot of innervation. The other nerve that you can see here, the smaller one that comes off into the leg, is going to be the posterior femoral cutaneous nerve, providing sensory innervation to the back of the leg. Sensory innervation to the back of the thigh is what I should say. The sciatic nerve is going to be provided to spinal nerves L4 through S3. It will separate into the, or divide into the tibial and common fibular nerves. Fibular means that the lateral and the leg, so if we come on down here, here is our common fibular nerve, which is going to split into a deep superficial version, just like our radial nerve does. Look at that, they're like the same thing. And then we will have our tibial nerve coming on straight down the posterior aspect of the leg here. So here we go, let's go take a little look at this. So this is the sciatic nerve, it's always so big and impressive here. It's pretty neat and easy to see why it can get impinged, squished, and cause pain. The other thing I wanted to show you is we're going to relate it back to our muscles that we know, right? So here's our piriformis muscle, bigger one here, and then we have our gemelae muscles and our obturator internus muscle, well a little bit of the tendon. So here's our superior and inferior gemelae muscles, and then we'll have our obturator internus between that, and here's our quadratus femoris, which we know from looking at the lower limb structures, and then coming out between piriformis and gemelae, it's going to be our sciatic nerve, and we actually have our superior and inferior gluteal nerves as well. All right, so what does a sciatic nerve do? A lot of things, but well, I guess first we'll talk about the posterior femoral cutaneous, only sensory to the back of the thigh, which is where the femoris. Sciatic nerve does everything else, so if we think about sciatic nerve in terms of skin, in terms of sensory innervation, we're going to have the lateral aspect, all these different colors here are all going to be branches of the sciatic nerve here. I'll replace the specific names with just sciatic nerve here, and then it's also going to provide the muscles of the posterior thigh right on its way down. So these are going to be the hip extensors and the knee flexors, and then our posterior muscles of posterior, well, we're going to look at the more specific branches that come off that for the leg, right? So there we go, posterior thigh. Let's look at these branches here. We just said sciatic nerve coming on down. The lateral branch is going to be the common fibular, and that posterior, the branch that stays in the back here, continue on down, is going to be the tibial. It does dive in deep beneath or deep to our gastrocnemius and our soleus, which is why we can see it here, right? So our gastrocnemius and our soleus have been reflected back, taken off to see the tibial nerve coming on down deep. Hopefully it makes sense that it's deep because it's providing all of these muscles innervation, and here's our common fibular nerve going through that lateral aspect here, right? Tibial nerve is going to provide motor innervation to the posterior leg muscles. to the posterior leg muscles. So these are our flexor muscles, right? So flexors of the ankle, flexors of digits of toes, and flexors of the big toe, right? toe, right? And our plantar foot muscles, which are, you know, basically all the brevis muscles. Okay, these are also, and then we look at the common fibular branch here. It's also called the perineal, if you've learned it that way before. It's going to come laterally in our legs, so we're going to come up here to see where it went laterally. We're going to have a superficial branch. Notice that it's, well, very clearly superficial, coming on down. And then we'll have our deep branches well here, diving in deeper. And then we'll have these two branches, our deep fibular and superficial. Oh, I had those backwards. I apologize. This is our superficial here because it's coming over on top of our extensoriculatum of the foot. And our deep one is coming in deep, deep to the extensoriculatum of the foot here. So all the motor of the anterior and lateral leg is going to come from this. So this is going to be our dorsiflexion, right? Pulling our toes towards us. But we're going to be done by the extensors here. So extensors, muscles of the leg, and then also our fibularis longus here and our fibularis brevis, which is deep to that. brevis, which is deep to that. All right. So just kind of contextualizing this stuff because it does impact a lot of people, many people. So if we have common injuries, if we look at common injuries, our gluteal nerves, if we talked about misplaced injections before, but if you're injected into the gluteal region at the wrong place, really, so here or here, maybe a little bit lower, like right here, you can get those superior and inferior gluteal nerves. And that's going to cause a lot of pain, right? And then also here with the sciatic nerve, one, it can be impinged up here, right? up here, right? But we can also have a herniated disc. So note that if we follow the sciatic nerve up, it's going to be coming out of or to have contributions from really this lower lumbar region. Our lumbar region is the most common place to have a herniated intervertebral disc. If it goes laterally or if it impacts these spinal nerves, it can cause sciatica, some extreme pain in the lower limb. We can also have sciatica due to impingement from really as it comes through all of these muscles here. Yep. So common clinical issues with that. All right. I'm going to, this is going to be in a weird spot. I apologize. It's supposed to be before. This is the back of the knee. And as we look at it here, we can see the sciatic nerve coming on down. I better change my color before you can't see anything. Here we go. Sciatic nerve is coming on down. This is the popliteal region. We're going to have popliteal structures, specifically vessels coming through here. Here is our tibial nerve coming in deep, right? We've taken off a lot of muscles to be able to see this. And then we're going to have our common fibular nerve, that lateral aspect, where that's going to split into the deep and superficial branches as well. Right. So we can see kind of a little bit of the knee right there. I can see the biceps femoris. Let's see where we're going to see that right here. Biceps femoris, because it's going to come down. Nope, nope, that's semi tendinosis. Nice and pretty tendon there. So we're going to have biceps femoris over here. Big muscle coming down and touching laterally in the leg there. in the leg there. Okay. Last thing here are reflexes. So this really kind of pulls a lot of our nervous system stuff together. We're not going to really worry about these structures right here, but we are going to look at this here, right? So reflexes, we know what a reflex is, right? An automatic involuntary reaction where our muscles contract, right? contract, right? Or our glands, our stimulator glands, right? It's another way to contract, or another thing that can contract in this way. or another thing that can contract in this way. And really it's some sort of survival mechanism that allows us to skip over sending information to the central nervous system, primarily the brain, right? right? The brain and then sending a response, a motor response back. We're going to skip really that majority of that spinal cord in the brain, right? We don't have to send it all up. We have this immediate response that can happen. So we're going to look over here. So we touch something hot or something that hurts. hurts. That sensory innervation is going to come up through our peripheral nerves, right? through our peripheral nerves, right? It's going to come through that anterior ramus, which is this one here. which is this one here. Primarily, I can't really think of anything that touches our back that makes us reflex. But anyways, here we go. It's going to come in, come in through our spinal nerve, notice that we're still mixed sensory in these regions here. Then we're going to send in our sensory information that dorsal root, dorsal root ganglia there into our spinal cord and through these interneurons that are located in the gray matter here, we can have an immediate reflex, right? right? It's going to communicate immediately or synapse immediately onto motor, right? There's no traveling involved. So here we have then our anterior horn, anterior roulette, anterior root into our spinal nerve, right? This is where our mixed sensory is. We're sending motor innervation out very quickly through the nerves that we talked about. If we're going to go and do our biceps break, yeah, it would be that muscular cutaneous nerve. That is the reaction, right? So I know this isn't actually really a reflex that we talk about, but I don't know, it's like a dad reflex, which is I think pretty good because I think he's like sleeping here. I think she says, wow. wow. Okay, so let's talk about this a little bit more clinically here, right? So we can use this also to test our muscles, but why are we testing our muscles? We can test if they work by flexing them, right? But we're going to use this myotatic reflex, myo, muscle reflex, to test our innervation, right? So we're using these external things to test our internal hidden things to see if they work, right? So we're stimulating these reflexes to see if there's any deficit in our nerves here, right? So we're going to stimulate or activate the sensory receptor, and we do that by whacking a tendon that is associated with a muscle, right? So here we're going to tap the tendon that's our biceps brachii, right? our biceps brachii, right? Muscle. That is going to send sensory innervation. to send sensory innervation. We have sensory to our muscles as well, right? Sensory innervation into our sensory nervous system, right? So we whack that tendon. It feels that it's going to send a sensory innervation into our posterior stuff here, right? Posterior dorsal root, and then we're going to go through this interneuron, and it's going to communicate and tell our muscle to contract, right? So the reflex. And so there's that information going out through our anterior stuff. Here's our spinal nerve, mixed sensory motor, the hoi too. If it's, again, our biceps brachii, it'll be musculocutaneous after it makes its way through the brachial plexus to our target organ, our effector organ, which is going to respond, right? So we can hit the tendons of our muscles to make them contract. That is a reflex, but if we know what that muscle is innervated by, that is a level of spinal nerve we can test to see if it works well, right? test to see if it works well, right? So to test our cervical spinal nerves, we are going to test things in the arm. things in the arm. So our biceps brachii and our triceps brachii. So if we test those, there's how you do a triceps brachii. It's going to be actually your forearm here, triceps brachii, excuse me, to test our cervical spinal nerves, right? right? Because these are resulting, this is the brachial plexus C5 through T1, sending innervation here to be tested. to be tested. All right. If we test our triceps brachii, that's our radial innervated by our radial nerve. That's what we're specifically testing, right? And then we'll have thoracic spinal nerves. We have abdominal reflexes. So if you like, I don't know, tickle the torso. That's not what I mean to say, but if there's specific places that you can stimulate this reflex to test our thoracic nerves, right? reflex to test our thoracic nerves, right? So then our lumbosacral spinal nerves can be tested through our patellar reflex, which I think is probably the most of us think about in terms of this. Our ankle, our achilles tendon, our calcaneal tendon, right? Which is attached to gastrocnemius and solus. And then our plantar reflexes as well. And if you think about, I think we talked about this, if you had a little baby foot, oh, this is a terrible baby foot. It's going to give me nightmares, right? If you run your finger down the medial side of that plantar surface, you're testing some of these muscles here. All right. And that is all I have for you. And that's the last recording.