hey everyone welcome to professor long selectors in anatomy and physiology these videos are being done to the coronavirus shut down they're gonna be quick and crude no editing all one takes so please bear with me I'm doing the best I can but as those of you who are in my class know I walk in asked where we left off and start lecturing I don't really follow I'm gonna follow my notes set but I have it in my head now so I'm trying to think about where we're going what we're doing and what's important so these videos are kind of made up as we're going along please bear with me now in the last video this is from my 24:01 students for part 1 a.m. P this is for lecture test 6 or what would be the equivalent of lecture test 6 we were talking in the last video about the ventricles and the meninges and cerebral spinal fluid one of the things I wanted to point out before I move on to the spinal cord is very often during development not very often but occasionally during development there are some there's some debris and some things that can block these interventricular for that parameter and as we continue to secrete the cerebral spinal fluid there's nowhere for it to drain and the lateral ventricles since the brain tissue is very very early in development that it's very squishy the ventricles get larger and larger and larger and you'll see these babies born with big swollen odd-looking shaped skulls and heads and they call that hydrocephalus water on the brain it's not water it's cerebrospinal fluid usually due to a blocked interventricular foramen occasionally the cerebral aqueduct can also get blocked but it's usually less often so you have to go in and put shunts and other things to drain the fluid off of things anyway I wanted to point that out there's a lot of stuff going on that you'll be dealing with also when someone does a spinal tap in order to sample cerebrospinal fluid I was talking about how it flows in the subarachnoid space well then what they'll do is they'll take a long needle they'll usually have a patient flex their spine and it's the same thing as do epidural block and an epidural block they'll put some fluid so some anesthetics outside in the between the two layers of dura mater I didn't show you both laters the dura mater but there on the model and in this epidural space they'll stick a drug that will numb the the roots of the nerves the spinal nerves we're about to do that Anatomy so I'll talk more about that but if you're going to do a cerebral spinal fluid if you're going to pull some cerebral spinal fluid off it's called a spinal tap they tap into the spinal fluid they actually have to an anesthesiologist will run a needle between your vertebrae and feel the dura mater and poke through it and thence and stop and the subarachnoid space and then pull some of the fluid off and then they can check the cerebrospinal fluid for bacteria viruses other things so it's pretty serious procedure and it requires a lot of touch and feel and so anesthesiologists are usually very very skilled they're very highly paid because they deserve to be anyway [Music] so now we're gonna start on the spinal cord itself this is chapter 13 if you're following in my notes it's on page 81 I'm going to go through all of these structures here and give you some definitions I'm probably going to give you more of a verbal definition than writing everything out or I may draw it so that you can see it okay when we look at the spinal cord there's a certain Anatomy to the spinal cord the spinal cord starts developing as a large mass but in order to fit in the smaller space it folds in on itself and it has a fold on the anterior and the posterior margins so if we were to do a cross-section of the spinal cord on the posterior margin there's a very tight group here called the posterior median sulcus I'm just going to put PMS there and then it folds out like this and then there's some branches that come off and swell up a little bit and do this so sort of the anatomy of your spinal cord and I'm going to draw a specific part of our spinal cord so that we can go over some of this all right and then we'll name all these structures in just a little bit on the anterior margin the gap is a little bit wider it's a little bit more open okay and then we would have all the same features on the opposite side okay these little branches over here we'll talk about it a little bit if not in this video eventually okay doo doo doo doo doo I didn't draw that very well on this side but oh well you'll bear with me here you'll see what I'm getting at and if you're in my class in the notes set I already have drawings of this I know that it's hard to learn to draw when I was a student taking neurobiology we had to do an essay test of this we had a certain amount of time to draw it labeled it and talk about all the functions I believe essay tests so the best way to learn but it's a lot of greedy we have a little hole in the middle called the central canal and then we have the gray matter now in the brain the gray matters on the outside the white matters in the center the spinal cord isn't the exact opposite the gray matter is in the middle and will flare out into these structures that are referred to as horns the gray matter will cross over to the opposite side of the spinal cord and form these structures kind of looks like a funky looking butterfly inside of it all right now this groove on the anterior margin is always a little bit wider gap and they call that the anterior median fissure okay fissures a wide gap a sulcus is a very tight group so anytime you look at a spinal cord you should be able to tell anterior from posterior of course the central canal is a hold of the center of the spinal cord so I'm gonna go down the list and I'm gonna point these features out and I'm going to tell you what you should be writing in your notes you can look this up the posterior median sulcus is simply a fold on the posterior margin of the spinal cord the anterior median fissure is a little bit wider gap or fold on the anterior margin of the spinal cord the central canal is a hole in the center of the spinal cord through which cerebral spinal fluid can flow up and down the spinal cord these three areas up here would be your three great horns and two your gray horn lateral grey horn posterior green horn and then these would be your three white columns over here these structures and I'll talk about the structures and the functions in just a minute we have some branches here that are called the roots these are the roots of a spinal nerve or all of these branches meet right about here it's called a spinal nerve I didn't draw mine quite long enough but you get the idea a spinal nerve is going to be one of the nerves that exits the spinal cord through the intervertebral foramen of your vertebrae so these roots there's we don't use the term anterior and posterior ntral in dorsal root the dorsal root has a swelling called the dorsal root ganglion we have a spinal nerve and then we have several branches this is called the ventral ramus this is called the dorsal ramus and this would be called the Rhema communities it's two different Ramah that communicate with each other and then we have an autonomic ganglion I'm drawing this one for a reason and an autonomic nerve all of this Anatomy we've kind of covered in lab but this is our autonomic ganglia nerve now before I get into all of this one of the things I want to show you I should probably done this first but hanging off the brain as the spinal cord comes down it starts to narrow but it has two enlargements this isn't drawn to scale but you get the idea okay so if I were looking at a human being this area would be near the cervical region we call this the cervical enlargement this is called the lumbar enlargement because it's the lumbar part of your spine where the lumbar vertebra is or are if I take a little piece of this off the little bottom part looks like a little comb so they call that the conus medullaris and coming off of this region there's a whole bunch of nerves that come off and your spinal cord actually stops short of the sacrum a little bit and your sacrum would be that fused group of vertebrae that have holes in it and these little pieces come off and come out of those holes like this and as they come off the conus medullaris they extend down longer than the spinal cord does and exit through the sacrum because it looks like a horse's tail that's called the cauda which means tail Akina okay equine is horse so cata Akina is the horse's tail at the end so let me give you some terminology here if we're following the table on page 81 we did the posterior median sulcus the anterior median fissure we did the central canal which is in the second part of the table or in the second table the cervical and lumbar enlargements are there because of this I want you to think about these terms I have a ferrant neurons coming into the spinal cord and efferent neurons coming out to my spinal nerves and they're going to feed all the muscles and all the organs and everything of the chest and the abdominal and pelvic regions okay but in humans because we have arms and legs we have a lot more nerves going to and coming coming into and out of the extremities the arms and the legs well wherever I have extra traffic coming in on a freeway we have extra lanes we have merging lanes on and exiting lanes off and so we have these enlargements to accommodate those nerves coming into and out of the spinal cord that serve either the upper extremities that would be the cervical enlargement that's an enlarged area the spun cord that accommodates additional innervation to the arms and legs and the lumbar enlargement to the arms I should say the lumbar enlargement accommodates the extra nerves going to the legs so we've knocked out most of this top part the conus medullaris is just a tapered cone at the end of the spinal cord the cada Akina is the thing that looks like a horse's tail it's the nerves and exit through the sacrum and we have a thing called the phylum terminalia which is a little piece of connective tissue at the bottom of the spinal cord at the tip of the conus medullaris that kind of ties it to the in the sacral canal because if we didn't hold it out to length it would start to try to retract and come up and it would stretch those nerves and damage them so the spinal cord has to be held the length by the phylum terminally okay which means the end hair it's a piece of connective tissue that holds the spinal cord to length all right so we knocked some of that stuff out I'm less concerned about all of these structures than I am about the next second table where we're going to talk about the functions of these other structures so you can read about the spinal meninges I covered those in the last video so we're gonna skip that part when you get to the second table I told you the central canal is a hole in the center of the spinal cord through each cerebral spinal fluid flows it's connected to the fourth ventricle now the posterior grey horn here's kind of what happens okay are our spinal nerves are a two-way street if you recall when we did the cranial nerves some cranial nerves are purely motor some are purely sensory and some are a loom of both all 31 pairs of spinal nerves are mixed nerves meaning they have both sensory and motor information coming into and out now if I have a sensory neuron coming in that sensory neuron no matter where it's going to come from is going to enter through the spinal nerve it's going to come through the dorsal root and they're going to synapse somewhere in the posterior gray horn the soma of this neuron is going to live in the dorsal root ganglion if you recall in one of the previous lectures a collection of neuron cell bodies in the CNS is usually called a nucleus or a center in the peripheral nervous system it's called the ganglion so one of the functions of the dorsal root is exactly this the dorsal root contains all income sensory neurons or afferent neurons that are entering the spinal cord from every level of the spinal cord we have the dorsal root containing the sensory neurons the dorsal root ganglion is going to contain the Samata of all sensory neurons entering the spinal cord okay doesn't matter which level rat and by the way I guess I should have done this earlier - your spinal cord is it tapers down is cut into segments like little coins stacked on top of each other and every one of these would have a dorsal root with the dorsal root ganglion eventual root and then a spinal nerve and then that's going to branch forming all these other structures that we've talked about okay these two little branches would be these two all of these would be these over here there's a spinal nerve okay and we would have this on both sides of the spinal cord dorsal root with the dorsal root ganglia on the ventral root spinal nerve dorsal ramus ventral ramus remind communities and then an autonomic ganglia on at least some parts of the nervous the the thoracolumbar region we have in some areas these autonomic ganglia so the next level of spinal cord would have the exact same Anatomy I'm not going to draw all the branches so every level of the spinal cord has the same structures they'll even have the same gray matter in white man now depending on what's going on the gray matter may be much larger and thicker with less white matter or in some parts of the spinal cord there's less gray matter and more white matter but nonetheless every level of the spinal cord is set up identically it has a pair of spinal nerves that are carrying sensory and motor information and each segment has its own pair of spinal nerves there's 31 pairs of spinal nerves there's 31 segments of the spinal cord okay so this may look a little bit different but every level from the cervical to the thoracic to the lumbar to the all of the sections of the spinal cord have a pair of spinal nerves have a dorsal root and a ventral root a dorsal regain neuron in the spinal nerve a little of this might change somewhat depending on whatever happens there not a lot okay now if I took one of these sections out and I flipped it this way that's what we would be looking at okay now now that we got some orientation I hope that makes sense to you it's kind of hard to explain visually what you're seeing there's explain verbally what you're seeing visually so when it comes to these structures one of the things we know is that the dorsal root always contains the incoming sensory axons and the dorsal root ganglion has the Samata of the sensory neurons entering the spinal cord the reason I did that first is because when I look in the lab and the posterior gray horn there are two major areas here that are nuclei there's called sensory nuclei because this is where the sensory neurons are going to synapse release neurotransmitter and then the neurons that receive that information at whatever level of the spinal cord is monitoring that part of your body they're going to send that information up through the spinal cord towards your brain so there's going to be a whole bunch of sensory neurons that live here that are just going to be receiving with their dendrites and everything but the so mots are here and they're gonna be receiving sensory input and they're going to send axons out and then up towards the brain through the white matter these are going to be myelinated axons so usually now because this nucleus here is receiving sensory information it turns out that the one that is further out at the tips of the the posterior horn is called this summit somatic sensory nucleus I didn't write that very well then did I this is called the somatic sensory nucleus okay I'll put SS and up here and I'm gonna explain this it stands for the somatic sensory [Music] nucleus now I want to get something across to you guys when we talk about somatic sensory what we're talking about is sensations from the surface of the body and from some skeletal muscle for the most part so if someone sticks you with the needle at a certain level of the spinal cord that information would come in through a sensory neuron through the dorsal root so the lives of the dorsal root ganglion and it would synapse and the somatic sensory nucleus if you tore a muscle would be the same kind of thing if you have some kind of visceral sensation you do have viscera in the body in the skin of the body like sweat glands and sebaceous glands so let's say you have an infected sebaceous glands it or a boil that's going to send a visceral sensation in here and at some levels of the spinal cord we're going to be receiving visceral information from the abdominal pelvic and the thoracic viscera if that visceral information is visceral sensory it's still going to come through the dorsal root the soma will still live on the dorsal ringing Leon but that neuron is going to synapse and neurons living a little bit deeper in the post to your grave horn and then they will send their axons maybe up a different bundle of axons here then this bundle of axons here okay so this structure is called the visceral sensory nucleus I'm not going to write sensory nucleus out but you get the idea this ro meaning soft organs your guts so I have a somatic and a visceral sensory nucleus so ultimately the function of the posterior grey horn is it contains both the somatic sensory nuclei and the visceral sensory nuclei which are going to receive sensory input from either side of the spinal cord so the function of the dorsal root ganglion is it contains the somatic sensory and the visceral sensory nuclei got it now we're gonna have some motor commands that have to come down from our brain when we take these sensations up to the brain and the brain interprets them we have to have motor commands come down and out of the spinal cord and it turns out we have two motor nuclei we have a somatic motor nucleus and a visceral motor nucleus the visceral motor nucleus is going to have the effects on the viscera of the body like if it's really hot and your sweat glands are going to squeeze out sweat that's visceral motor if we have any of our digestive system that needs to kick off that's going to be visceral motor if I'm moving my body my skeletal muscle that somatic motor somatic motor is always movement of skeletal muscle this role motor is always movement of some kind of visceral soft organ well it turns out that the visceral motor nucleus lives in the lateral great horn of each half of the spinal cord I would receive information from the brain synapsing here the motor neuron from the visceral motor nucleus would send its axons out this direction the ventral root is always going to have the axons of motor neurons exiting the spinal cord we don't have a ventral root ganglion because the neurons live and the nucleus of the spinal cord and will extend all the way out to the visceral muscle okay or at least to a ganglion and then to the visceral muscle we'll talk a little bit more about that so the visceral motor nucleus is in the lateral gray horn and that's the function of the lateral grey horn it contains the visceral motor nuclei of the neurons that will exit the spinal cord the anterior grey horn control contains the somatic motor nuclei when I say somatic motor I mean the movement of skeletal muscle and these neurons would receive information from your brain send their axons out the ventral root since the ventral root contains all motor axons exiting the spinal cord so when we look at the gray matter of the spinal cord we can see that the posterior gray horn has the somatic sensory and the visceral sensory nuclei and no the somatic recliner closer to the outside the this rule a little bit closer to the middle so posterior gray horn somatic and visceral motor nuclei they're going to receive input from sensory neurons coming into the spinal cord and send information at the BRIT up to the brain the lateral gray horn contains the visceral motor nucleus that's going to control movement of mode of smooth muscle and sometimes other viscera in the well their lives in the lateral gray horn the anterior great horn contains the somatic motor nucleus that's going to control skeletal muscle and every level of the spinal cord all the way down all thirty-one segments control different muscles or sensing sensing different parts of your skin so now we have these areas where excellence can cross in the white matter and in the gray matter because the right half of my brain is monitoring and controlling the left half of my body and vice versa some neurons at some point the neurons are going to have to cross to the opposite side some of them come in and cross pretty quickly some of them come in and go up aways and then cross some are coming down from the brain and cross at a specific location if the neurons are unmyelinated in meaning they have no myelin they're going to be in the gray matter so the gray comma suitors contain the unmyelinated axons that cross the spinal cord gray matter contains the unmyelinated axons the green commissaries gene the gray commissaries have unmyelinated axons the cross over the spinal cord the white comma suitors contain the myelinated axons that need to cross over to the opposite side of the spinal cord okay so anytime you see a white Comus here it's got white matter or myelinated axons anytime you see the gray commissaries it has gray matter or unmyelinated axons crossing this one so now now we're going to go look at the white columns these three areas of white matter are called white columns the reason they are called that is because if we were looking at the spinal cord in three dimensions so let's say I have a piece of the spinal cord like okay and here's the gray matter we're not focusing on that so and this is three-dimensional if I have some neurons that are going to exit a particular sensory nucleus down here and they're all going to be monitoring the same information from the same part of our body all of those neurons are going to travel together they get bundled into a tract remember a bundle of axons outside the CNS is called a nerve but inside the CNS it can be called a fascicle or tract while all of these axons are going to send their sensory information up to the brain and they're all going to be bundled together in the same cable let's say I have some other information coming in another level of the spinal cord it's going to synapse and I'm gonna have a bunch of neurons here that are all going to send their axons up to the brain through a different trap and if I look at it and one of these might be in the lateral white column the other one might be in the posterior white column at those levels of the spinal cord so when I look at this this looks like a column like the big thumbs up hold up buildings and things okay so they called the white matter of the spinal cord the white columns okay and what we contain in those white columns are tracts of axons a sending or descending the spinal cord okay so when it comes to the white columns all that we say about the white columns as the white columns contain tracts of axons a sending and descending the spinal cord we're going to talk about the tracts in the next video or in another video in just a little bit and there's specific tracks flowing in specific white columns at different levels of the spinal cord if you ever get into some deep neurobiology then you'll really understand why when someone enters a certain part of their spine the doctor knows which muscles or which viscera or which sensations should be disrupted they can order an MRI of certain part of the spine and see if there's compression a nerve that's interrupting flow into or out of that level of the spinal cord okay so now the dorsal root we already said contains the axons of neurons of sensory neurons coming into the spinal cord the dorsal root ganglion contains the Samata of those incoming sensory neurons and the ventral root is going to contain the axons of motor neurons exiting the spinal cord so you should know those three definitions finally the last definition on the table is the spinal nerve now if you're following them on we're doing the table now that's at the top of page 82 okay the spinal nerve there's you should know there's 31 pairs and that all spinal nerves are mixed they have both sensory and motor information coming in all right so hopefully that covers all of these structures at different levels of the spinal cord the last part I want to do is some sensory pathways okay I'm going to do the sensory pathways and the motor pathways actually I'm going to do those at a different video because this will take a little while and we're already pushing 30 minutes so I hope you know the anatomy of the spinal cord pretty well from this and you know what's going on in which structures you need to know where the sensory nuclei where the sensory of visceral motor and somatic motor nuclei are you need to know what's happening in the spinal nerves and the two routes now this leads to something important like I said before I'm gonna erase half of the spinal cord because that half I don't need but I want to show you something why this understanding this anatomy is important okay and then we'll wrap up this video and I'll move on to the next topic in the note set so if I were to look at the vertebrae the vertebrae are stacked like this with their intervertebral discs at every level of the vertebra if I were to look at the vertebra from a mobile you let's say I have a thoracic vertebra like this they have a spinous process that points down that's something unique about the Rasik very if I stab two vertebra together we have these articular facets that stick up the superior and the inferior articular facet and then I would have the intervertebral discs here that creates this intervertebral foramen and it turns out that your spinal cord is running right about here through the vertebral foramen and that's where a spinal nerve is going to exit through the intervertebral foramina at every level of the spinal cord your vertebrae are numbered they're named and the name is based on the location of the spine and the numbers c1 c2 c3 c4 until we get to c7 and then we get to thoracic nerve one that looks like a G but it's supposed to be C seven okay and then thoracic vertebra to thoracic vertebra three and so on and so forth okay something that's important I think anatomically for people to know is this in the cervical region the nerve comes before the spinal but before the vertebra for example if my spinal cord is running here I'm gonna have a nerve coming out like this on either side that cervical nerve number one and then I have cervical vertebra number one then I have cervical nerve - and cervical vertebra to c3 c4 comes before cervical vertebra for c5 c6 and I didn't draw this very well and then c7 comes off here so let me just put these vertebra in c5 c6 and c7 okay those got crushed sorry okay so you can see how in the cervical region it's the nerve first and then the vertebra so if someone has a pinched c2 or c3 a doctor knows to look between cervical vertebra c1 and c2 and c2 and c3 on an MRI or CT scan and see if there's any disk damage or loss of the gap between the vertebra and see if there's a crushed nerve let's say if you had a problem with the right side of your body in the cervical region or in your upper arm some numbness and tingling or loss of motor function okay now one caveat is after c7 we have cervical nerve eight there's only seven cervical vertebra but there are eight cervical nerves the numbering didn't work out as they went through so they just did this then after thoracic vertebra one is where nerve t1 comes off like this so in the cervical region the nerve comes before the vertebra so if someone says you know you have impingement at Snerd from cervical nerve five then you know it's somewhere between c4 and c5 vertebra you should be looking on the MRI for a lack of spacing or some kind of compression or a bulge - herniated disc okay c8 comes after c7 but before t1 it's an extra nerve and then after the thoracic vertebra all the way down the nerve comes after the vertebra and the thoracic and the lumbar in the sacral region okay just something interesting to note so that's the way the nerves are named now the reason I point that out is this let's say if someone is having some numbness and tingling in a certain part of their arm here your skin if you look there's a picture in your lab manual or in your lecture text as well let's say someone's arm is sitting out like this and you have your digits somebody had too many kids with their president and extra fingers so there's actually areas of your skin that are mapped out like this there's slices of skin that each nerve monitors so c8 2t1 is really monitoring sort of this side of your arm so if you had a crushed nerve in your neck you might be experiencing them so numbness and tingling in a certain part of your skin the doctor knows which nerves are going to go there if it was on this side then it'd be a different cervical nerve and they would go looking at where the damage is and because the nerves are both sensory and motor if the damage is up here it could be affecting sensory and motor if it's only sensory interruption so let's say you have interruption of synthesis here's something that Doc's do you go in and they'll rub your fingers does this feel normal does this feel normal does this feel normal does that feel normal and if you feel numbness and tingling in a certain part they know the damage is to the nerve down here or it could be up at the spinal cord and sometimes it's in both places so they can run a nerve conduction velocity or an EMG electro myelogram of your nerve to see if it's conducting properly if there's no problems down here then you look up at the cervical region maybe the damages appear and they know exactly which nerves should be affected because every swath of skin is innervated by a different nerve if you have sensory interruption only so not only do they rub all your fingers they'll ask you things like this pull up on my hand push down on my hand pull out on my hand push in on my hand and they have you do it on both sides if one side is weak but the other side feels normally strong then maybe you have something damaging the motor output if sensory and motor are both damaged then you could be pressing the nerve here or pressing both routes if sensory only is interrupted then maybe you know the damage is at the dorsal root the bulges in one particular direction if only motor is interrupts that level of the spinal cord and maybe the bulge is pressing on the ventral root because you're only interrupting motor output so knowing the anatomy of the spinal cord and these roots and the spinal nerve and knowing this Anatomy very often excuse me will tell the physician where in the spinal column do we need to be focusing an MRI or CT scan they don't want to waste all that money on all the films doing the whole spinal column if we know the issue is only in the upper extremities or maybe the lower extremities if you're having sciatica down the back of your leg they'll look at the nerves and the joint spacing and all of this if you have foot drop you're you can't hold your foot up and they ask you to sit down and point your toes at the ceiling and hold it if one foot continually drops you have motor damage to a nerve going to your foot if you can't feel your foot there's some numbness and tingling might be sensory damage at a certain level of the spinal cord that controls those muscles so that's really important for physicians and healthcare professionals to know so that you know why you're taking your x-rays or your MRIs or your CT scans and what you're looking for anyway that's why the knowledge of the spinal cord and the dorsal root being purely sensory the ventral root being purely motor output and spawning are being mixed and all of these parts sensory and motor are pretty important a little bit later we're going to talk about the actual white columns whether they're a sending and sensory or descending and motor so there's damage to the spinal cord you could know if it's in which particular column depending on AB it's sensory or motor and which part of the body is being affected we're not going to get into super detail anyway I hope you learned something I hope you had some fun while you did it hope you have as much fun as I did and I hope to see on the flip side in the next video thanks for watching