[MUSIC] Okay, so let's look at the spinal cord. The spinal cord is sitting within the vertebral column. And the vertebral column has different types of vertebrae. You can notice that the vertebrae up here look different from the vertebrae here. Do you see that these have very long processes and these don't and then, down here, the processes look different? We're not going to, we're not going to concern ourselves with the different types of vertebral, bones, but these are cervical, these are thoracic, and then we get into lumbar and sacral, vertebral, segments. And sitting inside this vertebral column, if we turn it around, inside here is the spinal cord. This is where the spinal cord has to, to sit. And it's, it's a, you know, it's a small area, but there's a little bit of room. It's unlike the cranium, where there's no room. The brain is right up against the, the dura is right up against the skull. In this situation, there's space between the dura and the side of the, vertebral column. So the spinal cord is inside of this column, but what happens during development is that the spinal cord does not grow as much as the vertebral column does. So, as a result, in the adult, the spinal cord ends at about right here. It ends about right there, which is, on me, it's, it's just a little bit below your ribcage. So it's ending right about here. That's the end of the spinal cord. But there is an anatomical rule, which is that every segment has to leave the spinal cord to go out and be a nerve through the appropriate, foramen, so, or hole. This is the hole. This is where nerves come out of. And the first cranial, or the second, nerve. Excuse me. The second cervical nerve, so these are cervical, thoracic, lumbar, sacral. And each nerve has to come out from this, the, the appropriately named bone. So cervical three has to come out by the third cervical vertebral. The thoracic ten has to come out by thoracic, the tenth thoracic vertebral bone. So, because the spinal cord is so much shorter than the, the vertebral column, what happens is that these nerves have to travel down before they reach the place where they're going to exit the vertebral column. So we have a spinal cord, spinal cord, spinal cord, but by here, the spinal cord ends and, but there are still nerves that are coming down to exit. And that causes a situation where we have, at the end of the spinal cord, we have all of these roots. These are roots that are on, on their way to exiting, below. So, in this case, here's the end of the spinal cord. This is the very end of the spinal cord. But it, by this point, there are all these nerve roots that are coming down to exit farther below. Let's take an-, a look at another one. So here, we can, we can sort of move aside these roots and we come to the end of the spinal cord right here. That's called the conus medullaris. It's the end of the spinal cord and below it are just roots. This is called a horses tail or cauda equina. So it's called the cauda equina and this cauda equina is down here. It's sitting in the vertebral column down here. So what's the importance of that? Well, the importance is that if you wanted to put a needle in somebody to try and either, test them to see if they have an infection in their cerebral spinal fluid or to administer drugs to them. Well, if you do it up here, you risk impaling the spinal cord and that's going to be disastrous. But if you do it down here by the cauda equina, as you put the needle in, imagine that you put the needle in, well, the nerves just kind of move aside. So if you put a needle in here, you're not going to actually puncture a nerve. They, they'll move aside. So this is a relatively, it's a relatively low risk, not without risk, but it's a relatively low risk, procedure compared to if you went up into the vertebral column at a place where you could actually puncture the spinal column. That would actually never happen. So that is the source of, what's called the lumbar puncture, but which is known, I think, in, common parlance as a spinal tap. So this is a spinal tap. You're doing a spinal tap down here where there's no spinal cord, but there's all these, all of, all of these roots. The cauda equina. So let's look at one more thing. What's probably the most common, type of pain that we have? Well, it would be, I think it would be, a close, call between a headache and a backache. They're both pretty common. But backaches are really common. What are backaches? What, what happens? Well, when the nerve comes out, it comes out from this, opening right here. And this opening, in this individual, is pretty, pretty big. But you can see, in this individual, there's much less of an opening. So look here, there's much less of an opening. Why? Because the discs, these things right here, these discs have, have compressed and there's less space between them. And so now there's less of an opening. The nerve can get pinched there. It can get squeezed. It can get otherwise, tickled. And that is not going to feel good, okay? And so this, this is, one of the big reasons for back problems is that these intervertebral foramens, these holes from which the nerves exit, are, get small as we age compared to what they hopefully are, normally. There are many other reasons for back pain, but that is one that we can look at on, on a skeleton. [MUSIC]
