okay so this is a typical spinal nerve and when we use this word typical we need to find spinal nerves that have all the components of all other spinal nerves now coming down from the brainstem the spinal cord forms and it gives off 31 pairs of spinal nerves one coccygeal 5 sacral five lumbar that actually form a plexus we actually have this area of the spinal cord called the lumbar enlargement why is it a little bit larger there because you have SEP sensory information coming from the legs adding to this spinal cord we called the lumbar enlargement we also have 12 just like thoracic vertebrae 12 spinal nerves 4 5 I better start to squeeze in a min more six seven eight nine ten eleven twelve thoracic spinal nerves one for each rib and then instead of seven like seven cervical vertebrae we actually have eight one two three four five six seven eight and that's because at the atlas which rotates around the dens of the axis okay we have a nerve coming out above and below and we have one below see two below see three below see four below see five below see six below see seven so we get eight nerves in the cervical region okay so we have 8 plus 12 plus five plus five sacral plus one coccygeal that's twenty thirty thirty-one spinal nerves there's also another remember there are 31 pairs spinal nerves on this side now some of these cervical ones form plexuses that run down our arm some of these lumbar ones form the lumbar plexus that run down our legs when we talk about a typical spinal nerve we're really referring to these thoracic ones one of these 12 thoracic ones because they have all the components of all other nerves so does l1 and l2 but these are thoracic spinal nerves and we're just going to use one of them to illustrate the layout of all of these now they don't necessarily run under a rib the way that the thoracic nerves do they might run down the leg or down the arm in a plexus but we have all the characteristics present there when we look at a thoracic or a typical spinal nerve okay real click quickly I want to run through a couple other parts of the spinal cord as long as we're here we have this cervical and lumbar enlargement but the spinal cord thins as it runs down our body and you've seen it real thick going through the foramen magnum it is not that large down here at the end this terminus or the end is what's called the conus medullaris that end we have our two enlargements the cervical and the lumbar but we have this overall narrowing of the spinal cord as we come down to the conus medullaris the spinal cord then gets anchored to the sacrum by a band of connective tissue down to the sacrum okay by this filum f AI lü m terminally I'm gonna ask you to come back and watch this video which I'm recording now and I'll put it under helpful resources kind of like I did with my diagram of drawing a vascular tree or my little road map to the joint structures and classifications I'm gonna add this video to helpful resources but you'll want to review these terms for your lecture exam for your final okay right now what we're concerned with is the typical spinal nerve there's one more structure that's not really on your word list I don't think in class and that's called the cauda equina the horse's tail and it's all these sacral and coccygeal nerves coming off that's the cauda tail equina horse the horse's tail okay now I'm going to cut the spinal cord here or somewhere here in the thoracic region and we're going to look at a transverse section of that spinal cord there's one half of the spinal cord there's the other half of the spinal cord okay now coming off the spinal cord and I'm just going to draw it on one side but remember that this is happening on both sides coming off the spinal cord we have something called a ventral root going into the back of the spinal cord we have something called a dorsal root now the spinal cord is opposite of the brain the brain is an Oreo cookie it's gray matter white matter grey matter grey matter white matter grey matter but the spinal cord has it's white matter on the outside and it's grey matter be broken al it's grey matter on the inside forming this butterfly this is all gray matter I can't find my like right here it is so this is a little different the brain which has gray Matt we'll talk about this in lecture more okay so I'm looking at the spinal cord and it's kind of got two hops with white matter on that are on the inside this posterior part is called the dorsal horn the ventral lateral horn or the lateral one and then the ventral horn same thing on the other side dorsal horn ventral lateral horn ventral horn that's where the cell bodies the neurons so mus are Butner actions and they're oftentimes myelinated those extensions are running up and down the spinal cord in the white matter and then they run out when we want to provide motor movement to a skeletal muscle or to smooth muscle and these nerves are going to go from the ventral horn where motor function through the ventral root now sensory information the sensation of feeling what we call a efferent function in from the dorsal root and on enlargement called a dorsal root ganglia are just where cell bodies for sensory information reside they pick up information from out in the periphery and they send it to the dorsal horn now this sensory information and motor function are conjoined the individual neurons of the sensory system and the motor system get wrapped up into this vast into this neural bundle called the typical spinal nerve that's what we see emerge from between two vertebrae that's what's poking out all this other stuff was in the vertebral canal that's what we see poking out and if we were in lab I would show you that yellow nerve poking out from the spinal column okay off this typical spinal nerve we're going to be going under a rib and you might recall from the ribbon atomy the sub costal groove that's where this nerve travels along with an artery and a vein and a little bit of lymphatics a neurovascular bundle a Van vein artery nerve in that order and a little bit of lymphatics that's going under the sub costal groove and it's going to send off what's called a dorsal ramus that then splits up to provide motor function to the muscles of the back and what else would we have back here we would have skin behind our spinal cord on our back this is posterior this would be anterior this dorsal ramus sends off cutaneous branches and muscular branches to the boat to the skin and muscle of our back but it also continues forward under that rib all the way down our sides continuing forward under that rib all the way anterior to the sternum this is called the ventral ramus the ventral ramus and the ventral ramus gives some lateral cutaneous nerves for the skin and the intercostal muscles it also gives ventral cutaneous nerves they go out to innervate the skin near the bellybutton and that the front of our body so this is the basic layout but the reason why we choose the thoracic spinal nerves to represent a typical spinal nerve is because it has this lateral horn you don't see the lateral horn in the lumbar region well after l2 l3 l4 l5 any of the sacral or coccygeal nerves you also don't see it up here in the cervical nerves and that's because this is where the autonomic nervous system comes from and we'll review this at another time but the thoracic nerve has an additional structure coming off of it and that additional structure gets us into this thing called the sympathetic chain and gets us back out of the sympathetic chain okay now I wish I had drawn this a little bit closer here this is like an additional spinal cord alongside the spinal cord it's actually bilateral we have them on both sides and they sit against the vertebral body here now this isn't drawn to scale this would be much much longer to get to the front of our body if I had a thoracic vertebrae here but what we have here is we have something called the white ramus communicants where those nerves can get into this chain and then go up and down it and the gray ramus communicants to get out of this chain there's also sometimes a back door exit into something called the splanchnic nerves but this is a sympathetic chain ganglia we're going to talk more about this right now we're just trying to learn the parts so I'm going to go through and label the parts of the typical spinal nerve and I hope that you understand that we're just choosing one of these nerves if it was in the cervical region it might instead of be taking this format we're not going to have this sympathetic chain here and we're not going to have that ventral lateral horn or the lateral horn it's just going to be traveling down the arm or in the lumbar region it'll just travel down the leg but we choose the thoracic region because it has all the components of all other nerves because only the levels of t1 to l2 have this okay let me label this we have the spinal cord and we're gonna have a dorsal Horn we also have a ventral horn we have gray matter and we have white matter we have a ventral root or I think your book will say root lint we have a dorsal root we also have a dorsal root ganglion or a DRG dorsal root ganglion important structure in physiology and anatomy of course now we have our typical spinal nerve and it's this whole thing you're gonna study for the course typical spinal nerve not just this part going forward but also all this is important we have a dorsal ramus or dorsal Ram I if we're talking about both sides Ram is plural ramus is singular we have dorsal cutaneous nerves supplying the skin and muscles or bringing a sensory information from them we have a ventral ramus traveling forward and off that ventral ramus this would normally be much closer here size-wise we have a white ramus communicants sometimes you see that written as communicant ace and a gray ramos communicants will learn about the color of these when we talk about the autonomic nervous system in lecture okay there's also kind of an escape route a secret door on the back end of that sympathetic ganglion sympathetic chain ganglion this whole thing okay we also off that Ventura Ramos have lateral cutaneous nerves and ventral cutaneous nerve these are the structures of a typical spinal nerve okay I just want to end with one example if somebody tickled you a sensory neuron would pick that up and it would send down an axon a message they travel backwards and it has a choice you can go this way or this way and they always go this way that's actually where the cell body for this cell is and it comes into the dorsal root and synapses or communicates with the dorsal horn that dorsal horn is then going to send information up to the brain through a second neuron now that could be somebody scratching your back or poking your belly button different nerves will carry it back now in response to that tickling you're going to contract the muscles the rectus abdominis the internal oblique your back might even tense and to do that you would send out through an alpha motor neuron this is where the cell bodies for these motor neurons called an alpha motor neuron are we learned about those a little bit with the muscles it's going to send out through the ventral root a motor nerve if I wanted to innervate the tracts I'd go back this way but I'm going to go forward and innervate these muscles of external oblique or the intercostal muscles to pull away from that tickly one of the things we can see is that ventral root only carries motor and that dorsal root only carries sensory but the spinal nerve carries both it's what we call a mixed nerve so if somebody damages coming right out of that vertebrae the nerve they're going to lose sensory function to that area of the body they won't be able to feel the tickling and they won't be able to contract the muscle but if somebody pinches the back they would still be able to control the muscles just fine but they would never be able to feel the tickling or if somebody damages the ventral root pinching the nerve in the front they would be able to feel pain in sensation and tickling but they would never be able to contract that muscle so understanding somebody's symptoms directs you to the appropriate anatomy of where the injury occurred if somebody damages the front of the spinal cord they're more likely to obtain motor function if somebody damages or gets a lesion at the back of the spinal cord they're more likely to lose sensory function okay I know this was a lot I'm gonna post it for everyone so I'm gonna stop this recording now I recommend you watch this on double speed because I kind of go slow in these videos and it'll sound a little smoother