 Okay, this is really exciting. So exciting because we're going to look at all of our spinal nerves. We're going to look at all of these guys right here. And how many of them do you think we have? Well, we actually have 31 pairs of spinal nerves. And I hope you remember that our spinal nerves actually travel out of the spinal cord. They travel away from the spinal cord, and they have to get out of that main hole in this hole right here. The spinal cord is traveling through that hole. And our spinal nerves have to get out of there so that they can go into the periphery and do their thing. And to get out, they have to travel through those intervertebral foramina. This is the body of my vertebra, vertebra, or vertebra, depending on where you want to place your emphasis. And you can imagine that the hole, the vertebral foramin, is approximately right here. And through that vertebral foramin is your entire spinal cord. Do you agree that if I was a rock star, I know you think I am, but every now and then, not so much. But if I was, do you agree that I could actually draw my little cross-section of spinal cord right on my spinal cord? I could cut it in half and draw it. And then do you agree that I actually would have, you know, a dorsal root ganglion? I just made that supposed to be one. There's my dorsal root ganglion. And it's actually going to combine and form a spinal nerve. Do you follow what I am doing right here? I'm trying to show you that all this is, is my big column of spinal cord running through the vertebral column. And then my actual spinal nerve, which we are totally comfortable with. We've seen these. We've gone in. We've gone out. We've taken our spinal nerve. We've named it. We've circled it. We've split it into an anterior ramus and a posterior ramus. That's going to come out through these inner vertebral foramina. These are structures that we learned already in the spinal cord. So look, do you agree then that I could draw, if this was, let's say, the body of my vertebra, and I could draw, I do not. Do you agree that I could draw, just for the fun of it, my inner vertebral foramina like this, and I could draw a stack of vertebral bodies? Do you agree with this? I'm just drawing my vertebral column. And do you agree that every single one of them is going to have an intervertebral foramine, and every intervertebral foramine is going to allow a spinal nerve to come out? Do you also agree that I could actually name my vertebrae? Every single one of them. You could name them. In fact, I'm going to name one. I'm going to name this one C7. And then you fill in all the others. Well, if this is C7, clearly this is C6, this is C5, this is C4, and clearly this is T1, and this is T2, easy. Do you agree that if I were the rock star, I know you think I am? I could actually draw my entire spinal cord, pulling through the vertebral foramina of each one of these vertebrae. And I could draw my little butterfly. Yes, you're cool. So you agree that we could pass the spinal nerve through this hole. Do you agree with that? Here's a spinal cord. Here comes an actual spinal nerve. My spinal nerve is going to split into a posterior ramus and an anterior ramus. And here's another spinal nerve that passes through that is going to split. It would be super awesome, like crazy awesome, to actually go in and draw your spinal cord in this space traveling all the way through here. That would be really awesome. More power to you if you choose to do it. No worries if you choose not to do it. Little green circle, which was my intervertebral foramin, is now actually surrounding my spinal nerve. Are you ready for one of the easiest things in anatomy? Did I just say that? I take it back. I don't know if it's going to be easy or not. Every spinal nerve has a name. Every spinal nerve is named for one of the vertebrae that it is next to. Here's the exciting part. If you know where C7 is, if you know the name of the vertebra, you know the name of the spinal nerve. Oh, and it's that easy. C7, the spinal nerve traveling superior through the intervertebral foramin superior to C7 is spinal nerve C7. Every spinal nerve traveling superior to C6 is who? Dogs, that's C6. The spinal nerve traveling superior to C5, dogs, that is C5. Do you see the pattern? It makes perfect sense. There's one place that it doesn't make perfect sense. Are you ready for that place? I'm going to put it in my favorite color so you never forget it because it's my favorite color. I'm sorry for this. The spinal nerve that is inferior to C7, what would you expect its name to be? T1, it's superior to T1. The bad news is no, it's C8. What? Really? It is. Nobody knows. I mean, that makes absolutely no sense. But since they made up C8 and they threw in spinal nerve C8 inferior to C7, vertebra, now we start numbering inferiorly. So who's my next spinal nerve? We're back into, we're in a different pattern. So which one is going to be inferior to T1? Is the T1 spinal nerve. Inferior to T2 is which spinal nerve? T2. So C8 marks this very interesting place, C7, marks this very interesting place where we do a flip-flop and we're no longer numbering for the vertebra until the spinal nerve. We're now numbering for the vertebra above the spinal nerve. That's cool. As long as you remember that it happens at C7 and C7, that's one of our, that's vertebra prominence. That's a marker, a surface anatomy marker. You can palpate your C7 and that's how you know that, okay, now we're going into thoracic vertebrae. So it's a good one to have this switch take place. It's kind of random, but it is what it is. Now, now you've got named spinal nerves. Now we're going to do stuff with these guys. The fact is, named spinal nerves go places that we can actually map where they go. Where does C8 go? It goes lots of places. These spinal nerves actually like braid. They mix and match with each other, which is totally wild. And then you end up with all these peripheral named nerves that you can trace back to a specific spinal nerve in the vertebral column. Let's look at a concept that each one of these spinal nerves has some fibers that travel to skin and they actually relay sensory information from your skin. So every single spinal nerve has some fibers that bring in sensory information from a certain part of your skin and that can all be mapped. In the next part, I will introduce you to my friend, Dermatome Man.