in this lecture I will be going over the spinal cord and nerves okay so the structure of the spinal cord is going to begin on the superior end through the largest opening in the skull called the fem and Magnum then the structure of the spinal cord is going to end at the level of a an adults L1 or L2 vertebrae but then you might be questioning so what occupies the space below the L1 or L2 vertebrae because you still have to go through the remainder of the lumbar and the Cal vertebrae that's going to be occupied by nerves that extend off the spinal cord so when you are born your spinal cord occupies your entire um vertebral fans from your base of your skull down to the sacral bones but then when you grow the spinal cord doesn't grow with it what grows are the nerves that extend off of it when it comes to the protection the spinal cord it is the same protection that's going to be around the the brain so there's going to be the bone which in this case instead of being cranial bones it is the vertebrae there's going to be the connected tissues of the meninges which are the same layers that surround the brain and then there's going to be the fluid called the cerebral spinal fluid or CSF fluid which is the same fluid around the brain as well so it is continuous around both structures so anatomically structures of the spinal cord right up here begins at the frame in Magnum so that's where it's going to attach to the most inferior structure of the brain called called the brain stem and then it ends right here roughly at the L1 L2 area what extends off of that then is going to be all of these neurons that occupy that space of the spinal or the vertebral forment so the main functions of the spinal cord is that it's going to be a two-way communication to and from the brain and the body so how the brain and the body connect is via the spinal cord it's also going to be important reflex center many of your major reflexes are initiated and completed at the spinal cord level so they don't involve the brain until after the spinal cord has done the reflex itself okay so the structures that are going to be protecting the spinal cord the structures are going to be the same that are going to be surrounding the brain so we have the most exterior which is going to be the bone so bone is going to be in this case the vertebrae in the middle of the vertebrae is the opening called the invertebral foramen and that's going to be where your spinal cord is going to be found protecting the spinal cord then are the three layers of the meninges so this is the same three layers that was surrounding it in the brain so we have the duramat which is a thick um tissue along the exterior um it's inelastic we have the arachnoid matter arachnoid means spider so this is a spider Webby type mesh uh webbing and then pamada which is a delicate piece of tissue directly on the spinal cord itself so those three layers are considered to be the meninges then when it comes to the spaces the spaces are also the same when it comes to the brain and the spinal cord so we have the epidural space because Epi means superficial or outside so this is going to be between the bone and the Duram matter we have the subdural because sub means below so this is going to be below the Duram matter and in between the Duram matter and arachnoid matter and then we have the sub arachnoid space so sub means below and that's going to refer to the arachnoid tissue now a couple differences here as far as when it comes to the spinal cord with the meninges is that the epidural space is a place in which we can put anesthetics when someone gets an epidural you've probably heard of a pregnant woman getting an epidural when she's in delivery and it's called an epidural because this is where those anesthetics are placed the subarachnoid space is the same when it comes to the brain where the CSF fluid or your cereal spinal fluid is going to be flowing so it's the same as the brain additionally what also is different is the fact that your PM matter has some extensions from it called denticulate ligaments the word DTI means it looks like a teeth a tooth I should say because it does but it's these extensions of the pmot that help to Anchor the spinal cord in its location so let's go over those structures again protecting so we have the vertebrae so that's going to be the vertebrae on the outside then we have our three layers of the maninis so we have the outermost layer here which is going to be the Duram matter then we have the middle layer which is going to be the arachnoid matter and then we have the innermost layer which is going to be the pamat and so we can see the webbing representing the AR noid the three spaces then we have the epidural space so that's going to be between the bone and the Duram mat so right there often times it's filled with fat we have the subdural space so that's going to be below the Duram Mater and then we have the subarachnoid space which is going to be below the Reid space or the Reid matter and that's where your CSF fluid is going to flow and then extending off to the side although it's not very well identified right through here those are the denticulate ligaments and so that's going to help keep the spinal cord anchored in its location okay it coming off your spinal cord are going to be the spinal nerves and spinal nerves are part of the peripheral nervous system so there's a couple uh more detail coming up about it when we get to the peripheral nervous system as far as the identification of the nerves but what's helpful for you to know is that spinal nerves attach to the spinal cord and they are paired together um there are 31 paired roots and they are named based upon where their going to be exiting the spinal column as far as the bones um when they exit together they often times are going to form interweaving with other spinal nerves and we call these nerve plexuses and we go over those when we get to the peripheral nervous system so those 31 pairs of nerves are going to be mixed as far as the fibers so they're both sensory and motor in it and how we identify them which is going to be exactly similar to how we identify um your vertebrae is we identify it by a letter indicating the region that it's found in and then the number indicating where it's going to extend off in the vertebral column in the region so if you recall when it came to the vertebrae you had seven cervical vertebrae 12 thoracic five lumbar five sacral and between three to fiveish coxial Bones this is very similar but there are a couple differences so instead of having seven cervical nerves you actually have eight so the eighth one um we say because you have one that extends off on top of C1 is where that eighth one comes in so eight cervical nerves 12 thoracic nerves which corresponds with the 12 thoracic vertebrae five lumbar nerves which corresponds with the five lumbar vertebrae five sacral nerves which corresponds with the five sacral vertebrae and then only one coxial nerve and because you have a range of coxal Bones this is not going to align with that when it comes to the spinal cord Anatomy there's going to be some structures that you can see so where your upper neurons from the upper limbs join the spinal cord it creates a slight enlargement that we call the cervical enlargement so it's just a widening really of mainly white matter from the neurons from your upper limbs that are joining the spinal cord then you have your lumbar enlargement which is also a slight widening because this is nerves from your lower limb that are going to be joining your spinal cord so you have a cervical enlargement and a lumbar enlargement then what happens is your spinal cord is going to taper and where it tapers is at a structure known as the conus medulas so the conus medis is the tapering end of the spinal cord roughly the L1 or L2 area and then the neurons that extend off of it we call this the K equina the word K means tail equina for horse so it looks like a horse's tail these are all nerves that are going to be extending off the spinal cord and that's what occupies that intervertebral framan space below the L1 L2 area additionally in the Cina there's going to be a structure that we call the philm terminali and the phm terali although it's in a bundle of nerves it is actually not a nerve it is a strand of pamer so it has kind of a shimmery silver color to it and its job is to Anchor the inferior end of the spinal cord to the coxial Bone so it does nothing with nerve impulses so let's identify those structures so here we can see on the left side the cervical enlargement representing where the um spinal cord gets slightly widened because of that additional nerves and then we have the lumbar enlargement down here representing where your um spinal cord is widening just slightly to allow the lumbar or the nerves from your lower limbs to join then we have the structure called the conus mellis so it forms a cone and then we have the cot equina that extends off of it so here's the cot equina as well and you can see that it looks like a horse's tail and then amongst this is that structure called the philm terminale that is not a nerve that is actually pamod to help to Anchor the inferior aspect of the spinal cord so here's another view of those structures so we have the conus medelis at number two we have the kot equin shown at number one and number one over here and you can see off the very very tip of Kus molis is number three which is that philm terminali and that's going to help to Anchor the spinal cord to the coxy bone because it's anchored on the superior end at the brain stem okay so a cross-section through the spinal cord is going to provide additional anatomical structures to know um so first of all there's going to be some divisions on the right and the left side but it's not fully separated the divisions can come from the fact that you have a deeper Groove and a shallower Groove the deeper Groove we call the ventral you can also use the word anterior median fissure fissures always mean deeper and wider and then on the posterior or dorsal side we have a median sulcus so median means middle sulcus means shallow so both of those structures are going to help to create a right and left half but not fully separate out your spinal cord the spinal cord is really no bigger than your pencil so it's quite small but there's so many anatomical and important structures that pass through there in the cross-section you're going to see that the gray matter is found in the middle it often times look like the letter H um sometimes it's called The Butterfly and then the white matter is going to be on the periphery or the outside of it in the middle of the spinal cord is a structure called the central canal and the central Canal is a small little opening it's a canal that's going to run the entire length of the spinal cord and this is filled with the cerebral spinal fluid to allow that fluid to flow down through the spinal cord and then out around so here we're going to have the central canal right there in the middle and then we're going to have our white matter around the periphery and we have our gray matter through the middle we can also see here that this is the vental also called anterior median fissure so it's a bit deeper and wider and then on the posterior side we have the dorsal also called posterior median sulcus so it's more narrower and not as deeper here's an actual picture through a spinal cord that can still show you those structures so on the an anterior median fissure so we can see that this is deeper and wider and then we have the posterior also called dorsal median sulcus so narrower and not as wide then we have the central Canal that structure right through the middle we have the gray matter here is the butterfly and then white matter along the outside so the gray matter is going to be that inner gray structure it often times looks like the letter H or sometimes people say it looks like a butterfly great matter remember means that these uh neurons are unmated so they don't have that fatty substance what's connecting the two halves of the spinal cord is What's called the gr commisure and the gr commisure is the crossbar in the letter H so if I do my letter H the gr commisure is the structure right here that's connecting the two sides it also is going to be surrounding that opening in the spinal cord called the central Canal now when it comes to the gray matter we can divide the gray matter into three horns and so those three horns are going to be the way that the spinal cord um is going to compartmentalize its neurons in the gray matter then we also have the white matter the white matter is along the periphery and so when it comes to the white matter this is composed of melinated axons that are going to go up and down the spinal cord um from the brain down to the body and from the body up to the brain now this matter is divided into um compartmentalizations that we call columns sometimes they're called finicula so there's a couple different ways that we can refer to it um both the gray matter and the white matter then have the locations of anterior lateral and posterior it's just a matter of if you're going to call it a horn when it's in the gry matter or calling it a column as well as the word finicula for the white matter so when it comes to the structure of the spinal cord it is important to note that the spinal cord has a particular anatomic iCal orientation to it so you have the anterior also called ventral root and this is going to be formed by all the anterior rootlets that extend off of the spinal cord um and this is going to contain all the motor information so motor means movement that's what's going to be extending off here and then the posterior root also called the dorsal root comes from the posterior rootlets and this is always going to um form the sensory or come from the sensory neurons so sensory always goes into the spinal cord on the posterior or dorsal side and MTAR always comes out another key structure that's only found on the posterior or dorsal side is a structure called the dorsal root gangion sometimes it's also called the posterior root ganglion a ganglion is a structure that contains nerve cell bodies so it's usually a widened structure and we only see this on the posterior route now what happens is the posterior anterior root eventually unite and when they unite together they form a SP nerve so a spinal nerve has mixed both motor and sensory to it but as it gets closer to the spinal cord it divides and all sensory information enters the spinal cord through the posterior that we also call dorsal root and all motor information is going to leave the spinal cord through the anterior or the vental root so here are those rootlets as compared to the roots so a really important understanding here is that the rootlets are these smaller more singular structures and then they group together to form a root and so you have posterior rootlets forming the posterior root anterior root lets forming the anterior root so a cross-section through the spinal cord what we see happening is out here is the spinal nerves remember spinal nerve has both mixed information of having both motor and sensory so what will happen is you have the information coming in on on the posterior side or the dorsal side that contains that posterior or Doral root ganglion so right through there it's a widen structure and there you can see that they're identifying the cell bodies by those structures there this is always going to contain sensory information so that information will go into the spinal cord then always leaving the spinal cord on the ventral root side is going to be all the motor information so it's going to go this way and so it's the same thing with every approach sensory goes in the posterior dorsal side mottar comes out the anterior or vental side always always the case and then they unite together and they're going to be forming a spinal nerve over here which has the motor and the sensory it's just efficient for your body to have both directions in the same structure just like a road has traffic going One Direction and traffic going the other direction on a road so when it comes to um going up and down the spinal cord if the pathways are going to go up we call them ascending Pathways if the pathways are going to go down we call them descending Pathways oftentimes sensory pathways are going up and so this is sending information to the brain and so this is sensory receptors that need to communicate to the brain motor pathways are going down and this is often times going to be information that needs to go from the brain to the rest of the body usually the brains to muscles to the glands of the body when it comes the motor pathways they are going to decussate um and decussate means to cross over this is talked about in the brain lecture where the decussation happens at the level of the medulla aanga that we call the um decoation of the pyramids what happens here then is that the right side of the brain controls the left side of the body and the left side of the brain controls the right side so this is your voluntary um control so the controlateral means that again 90% is controlled on the opposite side and that comes from those motor pathways crossing over um in the spinal cord area near your medulla oblongata or in the medulla aanga I should say at the decussation of the pyramids so here you can see an illustration showing you in the red is going to be the descending tracks carrying the motor information the blue is going to be the ascending tracks carrying the sensory it's wild to think about that in a structure no bigger than the size of your pencil that you have all of these various collections of nerves which is just crazy but that's how it's going to communicate is going up the spinal cord and down the spinal cord and out to any other muscles glands or neurons that it needs to communicate with so again here you can see that information is going to be going up in the sensory information and then motor is going to be coming down but as afor mentioned always sensory information goes through the posterior or dorsal side and motor information comes up the anterior or the vental side so it's still the same even with information going up or ascending and motor information going down or descending now covering your nerves you're going to have a couple different layers and so this um image is showing you those three layers and the names of the three layers are very similar to the muscle layers so we have the epineurium so Epi means outside nuum referring to the nerve that is the outermost layer that's for protection then we have the Paran nerve so per means around and perin nuum is going to wrap itself around a fasle so a fasle just like a muscle is a group of in the ca instead of muscle fibers neuronal fibers that are going to give it a grouping or a bundle so we call that a fasle and that's wrapped right a Paran nuum then on in each individual neuron we have What's called the endon nuum and endon nuum is wrapped around each Exxon which is not the same thing as the myin sheath so in a real neuron here we can see a transverse section through a neuron where we see the epineurium along the exterior then we have quite a few different facies in here you can see how that's also then subdivided as it is and so as it's subdivided through here each one of these facies has parin nuum surrounding it and then each individual nerve is going to have that individual fiber called an endon nuum one of the most important functions of your nerves is to create a map on your skin that we call a dermatome a dermatome map is showing what nerves from your spinal cord are going to inate your skin segments um and so this map is really functional for areas such as massage therapy physical therapy or when people lose sensation or touch or movement to particular areas of the body um dermatomes can help to indicate that there is Damage Done to one or more spal nerves because if you happen to have a location on the skin that's lost sensation then it can refer to the nerve that would go to that area um and so there are the nerves that go to the skin but there's also then the nerves from that spinal cord area that go to um internal organs this also then can lead to what's called a referred visceral pain so this is that phantom pain that exists at the skin level because something is happening deep down inside so for example the nerves that go to your heart are going going to have sister nerves that go to your skin in the dermatome levels and so often times when people have a heart attack they feel pain down one of the arms they can feel between the shoulder blades they can also feel it for example in their jaws because those are the nerves that went to that person's heart that are then to the skin level so here's showing you a map the dermatomal map of the body and so again this is just the skin segment that's going to be interated by those spinal nerves n and so this can indicate if there's something going on at a spinal cord level uh when it comes to these neurons as well as some internal organs that we know will have these neurons if it exists on the skin then it can indicate that something is happening with that organ so we have a couple clinical views here so the first one is called shingles so shingles is related to the idea of the dermatomes because what happens in shingles is there's a virus that um is the chickenpox virus that for people who have had chickenpox what happens is that you get Chickenpox and once you are um over or have healed from chickenpox the virus stays inside your body and then it stays latent which means it's not being active on one of your dorer root ganglions and it's going to typically remain latent until you get to adulthood then what can happen is the chickenpox virus can be stimulated to exist and it forms a patch of these raised bumps and blisters that creates burning and tinkling sensation and we call that shingles but what's fascinating about it is that whatever dorsal R ganglion that it um was found on it is going to um just create a map of that area so you can see that this person had shingles found on their T6 T6 level because that's where the rash is appearing and so that's fascinating that it helps us to be able to see the map of the body now for those of you who didn't get uh chickenpox because you got the vericella zuster vaccination you could still get shingles unlikely uh because you already have a vaccination for it um but it could happen um and then for those of us who have had chickenpox we can develop shingles but there are vaccinations out there to help protect against the possibility of developing shingles even if you've had chickenpox now um something that can happen to the spinal cord um via traumatic injuries we name them based upon what um damage is done to potentially what limb so if someone has monoplegia it's going to refer to one limb of the body uh that's what the prefix mono means hemia versus peria so hemia means half so the full right side or the full left side paraplegia means is it Superior or inferior when it comes to the traumatic injury quadriplegia the word quad means all four limbs are effective the damage that results from traumatic injury depends upon which spinal cord section is impacted as well as potentially what degree of compression of those segments are involved um oftentimes this type of traumatic injury is irreversible and it is permanent unfortunately another clinical view here is a lumbar puncture so a lumbar puncture can be done to analyze somebody's CSF fluid often times to see if there's some sort of infection that can be found in the fluid so what they do is they take a needle and they're going to go below the level of the spinal cord so usually L3 L4 because your spinal cord ends at L1 L2 so if they go below it then they're not going to puncture your spinal cord um and so they are going to stick a needle in between your vertebrae into this sub aroid space to get your CSF fluid and therefore they can analyze the CSF fluid to see if there's any sort of infection or um bacteria or injury happening there a lumbar puncture is the same thing as a spinal tap