hi guys this is peter from anatomy zone and in this tutorial we're going to take a look at the anatomy of the spinal cord so to begin with we'll look at the external features and then we'll move on to some of the basic internal anatomy of the spinal cord so what we're looking at here is a model of the vertebral column containing the spinal cord and you can see the brainstem at the top so rostral II or at the top the spinal cord is continuous with the medulla oblongata of the brainstem and in adults the spinal cord extends to the intervertebral discs between vertebral bodies l1 and l2 so I've just zoomed in to the lumbar region of the vertebral column and if I rotate the model around slightly you can see the distal end of the spinal cord terminating at this level between vertebra l1 and l2 so the spinal cord is essentially a segmental structure so it consists of 31 segments you've got 8 cervical 12 thoracic 5 lumber 5 sacral and 1 coccygeal segments and these segments give rise to spinal nerves so you can see the spinal nerves coming off either side of the spinal cord and these spinal nerves are paired so you've got spinal nerves emerging on either side of the spinal cord so you've got 31 segments of the spinal cord giving rise to 31 pairs of spinal nerves so just taking a look at the shape of the spinal cord itself you'll notice that it's essentially a cylindrical structure but there are two areas of the spinal cord which are slightly enlarged so you've got a cervical enlargement and a lumber enlargement so I've just switched over to a diagram to illustrate this and on the Left we're looking at the anterior aspect of the spinal cord on on on the right we've got the posterior aspect so you can see that there's this sort of bulging out of the spinal cord in the cervical region and the same in the lumbar region so the cervical enlargement corresponds to this segment c4 to t1 the lumber enlarged and corresponds to segments l1 to s3 and it's in these areas where the nerve plexuses which innervate the upper and lower limbs respectively emerge so this is why that area of the spinal cord is thickened because a lot of nerves supplying movement in the upper and lower limbs emerge from these areas so just coming back to the 3d model we're taking a look at the distal end of the spinal cord and you can see that it terminates in this conical structure which I've highlighted in green and this is known as the conus medullaris and extending from the tip of the conus medullaris you've got a strand of connective tissue which attaches the conus middle iris to the first coccygeal vertebra and this strand is called the filum terminale II so I've just drawn that on there and yellow so as you can see the lumber and sacral spinal nerves kind of hang down from the conus medullaris and they formed this kind of arrangement which looks like a horse's tail so the latin for this is called erta quiner and this is what that collection of spinal nerves is known as so just coming back to this model here with the vertebral column shown you can see how the pairs of spinal nerves emerge from between the vertebra so just drawing this on in green so you can see the 31 pairs of spinal nerves emerging from the intervertebral foramina between the vertebra so let's just take a look at how these spinal nerves attach to the spinal cord so what we're looking at now is the cervical region of the spinal cord and you can see that I've removed one of the cervical vertebra just so we can take a look at how the spinal nerves attach to the spinal cord so you can see that there's these little reutlitz which attach to the spinal cord and these reutlitz then converge to form the ventral and dorsal roots so if I just rotate the model around you can see that there's a root at the front so that's the ventral root and a root at the at the back so that's the dorsal root and these roots converge to form the spinal nerve itself and the spinal nerve exits the vertebral column via the intervertebral foramina so immediately after leaving the intervertebral foramina you can see that there's another division so the spinal nerve divides into a ventral and dorsal ramus so it's not actually shown clearly on this model here but the ventral ramus is a lot thicker than the dorsal ramus so essentially what you need to know is that the ventral ramus supplies the muscles and skin of the front of the body and the dorsal ramus supplies the muscles and skin of the of the back so if I just rotate the model around a slightly more you'll notice that there's this kind of swelling of the dorsal root so this is known as the dorsal root ganglion and this dorsal root ganglion contains the cell bodies of the primary afferent neurons which enter into the dorsal Horn of the spinal cord so the cell bodies of the ventral root are actually contained within the gray matter of the spinal cord so I'll talk about this in more detail in the next part of the tutorial but essentially you've got primary afferent neurons entering via the dorsal root and you've got the efferent neurons leaving via the ventral root so how can you remember which is a font which is effort and which contains sensory in which contains motor well you can use the mnemonic afferent arrives and efferent exits so with any structure in the nervous system afferent will mean information is brought to that structure and efferent means information is taken away from that structure so afferent arrives efferent exits and then with regard to the ventral and dorsal roots you can use the mnemonic same Dave so sensory afferent motor efferent same and then Dave dorsal efferent ventral effort so using that mnemonic you can work out that the dorsal root carries sensory afferent information and the ventral root carries motor effort information so in the next part of the tutorial we're going to take a look at a section a transverse section so if I just rotate the model round to the side like that we're going to take a section through the spinal cord like this and we'll look at the internal structure of the spinal cord and the layers that cover it so the meninges