We've been learning the axial skeleton, and now we've reached the most central axis of the axial skeleton, the spine. Alright. The spine, or also called the vertebral, or if you're feeling fancy, the vertebral column. It's going to be made of 24 vertebrae, plus the sacrum and the coccyx. And we have an image showing this here. We see the axial skeleton from the side. We see the skull, the vertebral column color coded so that we can label it, plus the ribs, and we also see here, the coxal bones added in so that we can see the pelvis. Now when you're learning the vertebrae, each vertebra doesn't have its own, you know, completely unique name. We put them into groups and label them that way. So the first group that we're going to learn is going to be the cervical vertebrae. Now, if you remember, cervical refers to your neck. So these are the vertebrae that are in your neck, and there are 7 of them. Now, when you learn the vertebrae, one way to name them is to take the first letter of the group that they're in. So here it's c for cervical, and then number them from the top of that region. So cervical, we start it would be the c₁, c₂, c₃, all the way down to the c₇. And I'll label that on our image here. This is going to be c₁ through c₇. Alright. The first two cervical vertebrae are unlike any other vertebrae, and so we're gonna go over those now. The first one is called the atlas. So the atlas, also just called C₁. The atlas, we're going to say, holds up your head like Atlas holding up the heavens. So your head sits on the vertebral column, and it sits directly on that C₁ on the Atlas. And if you know any mythology, Atlas, I actually forget if it's Greek or Roman, but Atlas had to hold up the heavens on his back for eternity. So your Atlas is holding up your head. And when you nod your head just like this, just a little bit, what you're actually doing is the head is rocking back and forth on the atlas. Now, your C₂ or your axis, well, it's easy to remember these two together because they're both a word, so I always remember them together, the atlas and the axis. Well, the axis allows the head to turn on an axis. So when you do this, what's actually happening is that Atlas is turning back and forth on the axis. Okay. With that, let's talk about our other regions. As we go down, we reach the thoracic vertebrae. There's gonna be 12 thoracic vertebrae. Remember, your sort of chest region is your thoracic region. And what makes the thoracic vertebrae unique is that they all articulate with ribs. Each thoracic vertebra articulates with two ribs, one on each side. And we can number these t₁ through t₁₂, so we're gonna see it right here. In orange, we have the T₁ through T₁₂. Going down, we reach the lumbar vertebrae. And if you remember lumbar, that refers to your lower back. There're gonna be 5 lumbar vertebrae, and these are gonna be the biggest, thickest, heavy vertebrae because they're bearing so much more weight. The vertebrae, as you go down, get bigger because they carry more and more weight. So we're gonna name them 1 through 5, and we see right here L₁ through L₅. Oops, I wrote a 3. There we go. L₁ through L₅. Okay. Finally, we've reached the sacrum, and the sacrum is gonna be the back part of the pelvis. So together, the sacrum and the coxal bones, your hip bones, make up the pelvis. Now, the sacrum is sort of part of this vertebral column. It's a single bone, but it's grown from 5 fused vertebrae. And so you can still see and identify the different bones that fuse together to make it, so you can label those bones s₁ through s₅ if you need to. So we can see the sacrum here. I'm just gonna circle it. Here is the sacrum, that back part of the pelvis. The final part of the vertebral column is going to be the coccyx, and the coccyx, that's your tailbone. This comes from 3 to 5, typically 4, fused vertebrae. So these small vertebrae fuse together. Usually, they fuse into one bone. Sometimes it's more than one bone, but usually it's 1. And you can see it just right down here, your coccyx. Now the name coccyx comes from ancient Greek, and in ancient Greek, coccyx refers to the cuckoo bird, because the ancient Greek animists thought that it looked like the beak of a cuckoo bird. Okay. Now, as we look at our spine, you'll see your spine is not straight like a flagpole. It has curvatures, and specifically, we're gonna name four curvatures of the spine. You see them right here. We have 1, 2, 3, 4. It sort of makes this wavy line as it goes up, and those four curves are just named after the regions of the spine, named after the vertebrae that are in that region. So we have the cervical curve, thoracic, lumbar, and sacral curve. And instead of just being straight like a flagpole, having that bend, that just gives your spine just a little bit of spring to it. Right? So it acts a little bit like a spring, makes it not such a rigid pole. Now the other thing that you'll notice about these vertebrae is that they're not right on top of each other. In between each one, you have this little cushion of connective tissue and cartilage, and these are the intervertebral discs. So this is cartilage and connective tissue that cushions between the vertebrae. Right? So you don't want just bone on bone banging down on each other, and you also want to have a little bit of flexibility in your spine. The spine isn't super flexible, but it can move. And when it's moving, that's those vertebral discs just squishing down and stretching just a little bit between the different vertebrae. Now importantly, these vertebral discs, we'll just note they are absent between C₁ and C₂. And if you remember, that's your atlas and your axis. And that's because instead of being sort of fused with these vertebral discs, where it just has a little bend between them, those you can actually twist back and forth. Alright. That's our vertebral column. I'll see you in the next video.