Neuroanatomy S1 E2A: Introduction to the Spinal Cord #neuroanatomy #spinalcord #medicine

together with the brain the spinal cord makes up the central nervous system and is composed of bundles of afferent and efferent nerve fibers that connect the central and peripheral divisions of the nervous system today we're going to look at the structures that make up surround and protect the spinal cord we're also going to see how motor and sensory neurons come together in the developing nervous system the spinal cord is a cylindrical structure that is a direct extension of the brainstem extending from foramen magnum of the skull all the way down the vertebral column of the spine within the vertebral column the spinal cord is surrounded by meningeal coverings which are continuous with the meningeal coverings of the brain the meningeal coverings surround and protect the brain and spinal cord and help stabilize them within their bony surroundings the outermost layer is the dura mater which forms the dural sac that surrounds the entire spinal cord when you open the dura mater you can see the spinal cord and the next meningeal layers in this specimen we have opened the door from the posterior surface just deep to the dura mater is the next meningeal layer the arachnoid mater it receives its name from its spider web-like appearance during life the arachnoid mater is ballooned up against the dura forming a subarachnoid space between the arachnoid mater and the innermost meningeal layer the Pia mater the subarachnoid space is filled with circulating cerebrospinal fluid this fluid cushions and protects the brain both physically and chemically the spinal blood vessels are suspended within small strands of tissue called arachnoid trabeculae that connect to the PIA mater the Pia mater is the innermost meningeal layer and adheres tightly to the surface of the spinal cord importantly the Pia mater gives rise to a number of outgrowths that function to anchor and provide stability to the spinal cord paired ribbon-like extensions of Pia mater extend laterally and attach to the dura along the length of the spinal cord these are known as then tick youlet ligaments and they arise medially in between the anterior and posterior roots of the spinal nerves another peel outgrowth is the phylum terminally which arises at the distal end of the conus medullaris it stabilizes the spinal cord by anchoring it distally to the bony coccyx the tapered end of the spinal cord is called the conus medullaris this is where the spinal cord ends the conus medullaris is surrounded by long lumbosacral roots collectively referred to as the cauda equina because it resembles a horse's tail so let's look at the arrangement of nerves as they emerge from the central nervous system shown here is a diagram of what the central nervous system would look like from behind the upper swollen end of the central nervous system is the brain and the elongate structure here is the the spinal cord that extends throughout the vertebra or are long the back let's look at the numbers or arrangement of nerves and their bones in relation to the central nervous system the brain gives rise to 12 cranial nerves that are indicated by Roman numerals Roman numerals one through 12 so 12 cranial nerves and the skull is associated with the brain and protects the upper end of the nervous system is in fact the skull the rest of the central nervous system is the spinal cord and we divide it into a number of regions based on the bones that they're associated with and the body regions the first or upper region of the spinal cord is what we call a cervical region or neck region and that region gives rise to eight cervical nerves indicated by Arabic numerals one through eight and there are actually seven cervical vertebra see one to c7 in Roman numerals the next area is the thoracic region this region is associated with ribs and the nerves that emerge from the spinal cord in that area are also associated with those ribs there are 12 thoracic nurse T 1 2 T 12 and there are 12 thoracic vertebrae T 1 2 T 12 you'll notice that the vertebra are in Roman numerals and the nerves are in Arabic nermal's new numerals and that's how we differentiate between the two the next region of the spinal cord is the lumbar region the region of the lower back these vertebra are not associated with ribs and there are five lumbar vertebra l1 to l5 and accordingly there is five lumbar nerves l1 to l5 and again these occur on each side the nerves they're paired next region down is a little bit different than the other regions here you do have five sacral vertebra that develop embryologically but they fuse into one single bone that we call the sacrum but because there are initially five sacral vertebra there are also five sacral nerves the last end of the spinal cord gives rise to usually one coccygeal nerve although there are one two four coccygeal vertebra that develop embryologically these fuse to form one structure called the coccyx as we survey the gross anatomy of the spinal cord you can clearly see two areas where the spinal cord becomes enlarged the more superior swelling is the cervical enlargement corresponding to the segment's c4 to t1 of the spinal cord this gives rise to the spinal nerves which will form the brachial plexus and provide innervation to the upper limb the inferior swelling is the lumbosacral enlargement it corresponds to the L 2 to s 3 segments of the spinal cord these segments of the spinal cord give rise to the spinal nerves which will form the lumbosacral plexus and provide innervation to the lower limb so let's have a look at the arrangement of the spinal cord and related structures in the back the first cervical vertebra would be in about this position and the last vertebra or the coccyx would be down in about this position in this model the spinal cord is indicated in yellow and the dural sac is indicated in blue the first thing that you notice on this is that the spinal cord ends in the back does not go all the way down and correlate with the end of the vertebral column which is down here there's a couple of landmarks in the back that you can use to position the end of the spinal cord in the back the top of the pelvis here or the iliac crest marks for you the approximate position of the spine of l4 if you feel up to spinal levels it'll take you to l2 the one spine above that is l1 and the spinal cord ends approximately at the intervertebral disk between l1 and l2 which is a lot higher than the last vertebra and the vertebral column or the coccyx you'll notice that the dural sac extends all the way down the vertebral column there's a couple of other little landmarks down here that are just out of view behind the belt that are sacral dimples and they mark the approximate position of s2 which is where the subarachnoid space ends and the subarachnoid space contains the cerebral spinal fluid and you'll notice that there's what's called the lumbar cistern that extends from the end of the the spinal cord at approximately l1 l2 down through to approximately s2 where all you have here is cerebrospinal fluid and the the roots of the spinal nerves that are descending to emerge from the vertebral column lower down

Channel: UBC Medicine - Educational Media

Views: 1,516,337

Keywords: Neuroanatomy (Anatomical Structure), Central Nervous System, UBC, University of British Columbia, Faculty of Medicine, MedIT, Educational Technology, Claudia Krebs, Zachary Rothman, Canada, Vancouver, BC, Medicine, Anatomy, Dissection (Taxonomy Subject), Gross Anatomy Laboratory, Flexible Learning, 4K, Toby Gorman, richard neufeld, echocloud, gloo studios, gloostudios, james wallace, Wayne Vogl, gray's anatomy

Id: IAwk0pshcDE

Length: 10min 32sec (632 seconds)

Published: Sun Jan 19 2014