hey guys this is Peter from Anatomy Zone and in this tutorial we're going to take a look at the blood supply to the spinal cord so I'll first look at the arterial Supply and then I'll move on to the venous drainage so with the arterial Supply essentially you have two sources which Supply the spinal cord you've got one source which arises at the level of the medulla oblongata inside the cranial cavity and gives off branches which descend vertically down the length of the spinal cord and you've also got vessels which feed in at each different segmental level so these are the segmental spinal arteries or the feeder vessels as they feed in at each different vertebral segment so first we'll take a look at the vertical vessels which run the length of the spinal cord so looking at this model here with the vertebral column the spinal cord and a few blood vessels you can see the vertical artery here coming off the subclavian on either side and we'll just take a look at the right side and you can see that the vertebral artery Rises up and passes through the transverse processes of the cervical vertebra so this vertebra here is C6 and the vertebral artery passes first through the transverse process via the transverse foramen and ascends up towards the cranial cavity so after entering the cranial cavity through the foramen magnum the vertical arteries anastomodes to form the basal artery but what we're interested in is the vertebral arteries giving off the anterior spinal arteries so you get this anastomosis coming off the vertebral arteries on either side and this forms the anterior spinal artery and this artery runs down the spinal cord its entire length and it runs anterior to the ventral median fissure or the anterior median fissure so that's one of the vertical vessels the other two vertical vessels are the posterior spinal arteries and you've got two posterior spinal arteries now if we just rotate the model around so we can look at the posterior aspect of the spinal cord so posteriorly you've got two branches given off from the vertebral arteries which form the two posterior spinal arteries so these run the length of the spinal cord down the posterolateral aspect of the spinal cord so you've got one anterior spinal artery and two posterior spinal arteries so these are the three vertical arteries which originate in the cranial cavity and descend the length of the spinal cord so now we'll take a look at the second arterial source to the spinal cord so this is from the segmental vessels and they're called this because they feed in to the spinal Corda each different segmental level so they enter by the intervertebral foramina along with the spinal nerve roots and these segmental vessels are given off by different vessels depending on the region of the spinal cord that they Supply so in the cervical region you've got the vertebral and deep cervical arteries which give off these segmental spinal arteries and then in the thorax you've got the posterior intercostal arteries which give off these segmental arteries and in the abdomen the lumbar arteries give rise to the segmental arteries so for simplicity's sake I'm going to zoom in to the thoracic spinal region and we'll take a look at the segmental blood supply there so we're looking here at the thoracic region of the spinal column and what you can see is that I've removed one of the thoracic vertebra and you've got the thoracic aorta anteriorly you've got the spinal cord behind and you've got the dorsal and ventral Roots attaching to the spinal cord and then coming off the thoracic aorta you can see the posterior intercostal artery so at the thoracic level the segmental spinal artery is given off from the posterior intercostal artery it then divides into two branches you've got the posterior radicular artery and the anterior radicular artery and these follow along the dorsal and ventral nerve Roots so also you'd have the anterior spinal artery running down in front of the ventral median fissure like this and you'd be able to see one of the posterior spinal arteries running down the posterolateral aspect so at every vertical level you've got this arrangement of a segmental spinal artery giving rise to a posterior and anterior radicular artery but at some vertical levels you've got another branch called the segmental medullary artery so this comes off the segmental spinal artery and it actually directly joins to the descending vertical arteries so the anterior and posterior spinal arteries so this doesn't happen at every spinal level but it's something to be aware of and it acts to sort of reinforce the blood supply that's provided by these vertical descending arteries so also of note is that the largest segmental medullary artery is known as the arterial radicularis Magna which essentially is a descriptive Latin term for what I just said so it just means the great radicular artery and this arises in the lower thoracic and upper lumbar regions and it helps to essentially reinforce the blood supply to the distal parts of the spinal cord so that's the the arterial supply to the spinal cord so next we'll talk about venous drainage and what I'd like to do is just switch over to a cross-sectional diagram to explain the basic basic aspects of this system so we're looking now at a cross-sectional diagram of the spinal cord and its roots so just before we talk about the venous system I'll just draw onto this diagram what we've talked about so postal laterally you've got the posterior spinal arteries and anteriorly in front of the ventral median fissure anterior medium fissure you've got the anterior spinal artery and then you've got these segmental arteries given off by different arteries so we talked about the thoracic level so they were given off by the posterior intercostal arteries so the segmental arteries on either side and the segmental spinal artery is divide into posterior radicular arteries and anterior radicular arteries and then we also discussed that at some vertical levels you've got the segmental medullary arteries directly given off from the segmental spinal arteries to join the vertical arteries so essentially you've got a similar structure to the venous drainage system of the spinal cord so you've got these longitudinal veins which run down the length of the spinal cord you've got anterolateral and posterolateral veins which sit either side of the dorsal and ventral nerve Roots so I'm just drawing these on and then as well as the anterolateral and posterellateral veins you've got an anterior and a posterior spinal vein so all these veins that I've just mentioned basically drain via anterior and posterior radicular veins and these veins then drain to a venous plexus which sits in the extra dual space so you can see the dura Marta covering their spinal cord here so this venous plexus is known as the internal vertebral venous plexus and it is situated in the extra dual space outside the dura Mata so then what happens the blood from the internal vertebral venous plexus then drains to another plexus which is the external vertical venous plexus and the blood then essentially drains back into the big systemic veins so the ascending lumbar vein and the a zygous veins the hemia zygos and the a zygos veins themselves so that's the blood supply to the spinal cord