The Spine: Study with Video Lessons, Practice Problems & Examples

The vertebral column, or spine, consists of 24 vertebrae, the sacrum, and the coccyx. It is divided into cervical (C1-C7), thoracic (T1-T12), and lumbar (L1-L5) regions, with the cervical vertebrae supporting the head and allowing movement. The thoracic vertebrae articulate with ribs, while the lumbar vertebrae bear significant weight. The sacrum, formed from fused vertebrae, connects to the pelvis, and the coccyx, or tailbone, consists of fused vertebrae. Intervertebral discs provide cushioning and flexibility, except between C1 and C2, which allows for rotation.

Spine (Vertebral Column)

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.

The Spine Example 1

Our example wants us to match the section of the spine to the type of vertebra found there. Then it wants to fill in the number of vertebrae found in that section and determine if the curve of the spine is concave or convex posteriorly in that region. Alright. So as we look at our image here, we see a spine, we see the curves of the spine, and I can tell that this is a side view of the spine, and it wants us to know anterior and posterior here. So this is the anterior side and this is the posterior side. So if this was in a person, this person would be facing forward in that way. What I can tell is that all these processes are sticking out the back. Those are those bumps that you can feel in your spine as you touch your back. Alright. So here we have our different regions. They're listed in alphabetical order, not in the correct order. So let's go through them and match them up. Alright. Cervical. So which region is your cervical vertebrae? Well, remember, cervical, that refers to your neck region. So the cervical region is going to be at the top here, and that is going to be A. How many bones in your cervical region? Well, we said it was C1 through C7. 7 cervical vertebrae. And now this curvature question, concave or convex posteriorly? Alright. Before I answer that, I just want to remind myself of concave and convex because it always gets me confused. So I always remember this trick that I learned in elementary school. I draw a curve, and I say, alright. Which side looks like you're walking into a cave? Well, that's the concave side, which means that the other side is the convex side. So as I draw the curve on this cervical vertebrae, it's sort of curving that way. So that to me looks like that concave side is facing posterior.

Okay, that brings us to the coccyx. So which letter here is the coccyx? Oh, remember the coccyx? That's your tailbone. So it's down here at E. I actually think not all the bones are there, but we're not going to worry about that. So the coccyx may be E. How many bones make up your coccyx? Well, your coccyx is a single bone, but I'm going to put in parentheses here 3 to 5, or you could just write 4. Remember the coccyx is made of these smaller bones that fuse together in an adult to make that one bone of the tailbone. Alright. Finally, the curvature here. Before we did say the curvature though, I just want to stress and remind you we had 4 major curves of the spine. The coccyx is not one of those major curves of the spine that you need to remember, but we can still see the curve. So I'm going to draw that curve that I see here in. And as I look at that, well, which side is facing posteriorly? Well, that looks like the convex side.

Next up, we have lumbar. So which one is your lumbar vertebrae? Well, remember, lumbar, that's your lower back. So those are those big, heavy vertebrae of the lower back. So as I look here, lumbar is going to be C. How many lumbar vertebrae do you have? Well, see we said lumbar. It was L1 through L5. 5 lumbar vertebrae, and I'll draw in the curve. Alright. That's the curve I see for those vertebrae. So which way is that facing? Well, the posterior side looks like it is concave.

Which brings us to the sacrum. Alright. The sacrum, which letter on here is the sacrum? Remember the sacrum is that bone that's part of the vertebral column, but it connects it to the pelvis. So I can see here that's going to be D. So D, the sacrum. How many bones make up your sacrum? Well, definitely only one bone in the sacrum. But again, I'm going to put in parentheses 5 here because remember the sacrum is made of 5 fused sacral vertebrae. Definitely only one bone in an adult. Alright. Curvature. Well, I'm going to draw in the curve again. Alright. So is the convex or concave side facing posteriorly? Well, to me, that looks like the convex side is.

Lastly, we have the thoracic vertebrae. We have only one letter left, but hopefully you could figure out anyways. Alright. So lastly, we have B here. Remember, thoracic, that refers to sort of the chest region, the area of your rib cage. So thoracic vertebrae are going to be B. How many do you have? Well, just like pairs of ribs, you have 12 thoracic vertebrae, and we can draw in the curve. As I draw in that curve, it looks like the side is facing posteriorly. Now just a quick reminder on the curves, as you go down, these curves should alternate. So it should be, concave, convex, concave, convex. Then remember the coccyx isn't an official curve, and that gives your spine that little bit of a spring action that it has. Okay. So with that, we've named the vertebrae. We've figured out where they are. We've said how many there are, and we've identified the curves. Good work. More problems to follow.

In a skiing accident, Marcio broke his T2 and T3. Where is his injury?

• A. In his neck.
• B. In the middle of his back.
• C. In his upper back.
• D. In his lower back.

Which part of the spine will have fewer individual bones as you age?

• A. Cervical vertebrae
• B. Thoracic vertebrae
• C. Lumbar vertebrae
• D. Sacrum

Here’s what students ask on this topic:

What are the different regions of the vertebral column and how many vertebrae are in each region?

The vertebral column is divided into three main regions: cervical, thoracic, and lumbar. The cervical region consists of 7 vertebrae (C1-C7), which support the head and allow for its movement. The thoracic region has 12 vertebrae (T1-T12), each of which articulates with a pair of ribs. The lumbar region contains 5 vertebrae (L1-L5), which are the largest and bear the most weight. Additionally, the sacrum, formed from 5 fused vertebrae, connects to the pelvis, and the coccyx, or tailbone, consists of 3 to 5 fused vertebrae.

What is the function of intervertebral discs and where are they absent in the spine?

Intervertebral discs are cushions of connective tissue and cartilage located between the vertebrae. They provide cushioning and flexibility to the spine, preventing bone-on-bone contact and allowing for slight movements. These discs are absent between the first two cervical vertebrae, C1 (atlas) and C2 (axis), to allow for the rotation of the head. This absence enables the atlas to pivot around the axis, facilitating head movements such as nodding and turning.

What are the unique features of the first two cervical vertebrae, C1 and C2?

The first cervical vertebra, C1, is known as the atlas. It supports the skull and allows for the nodding motion of the head. The second cervical vertebra, C2, is called the axis. It has a unique structure called the odontoid process, or dens, which acts as a pivot point for the atlas, enabling the head to rotate. Together, the atlas and axis facilitate a wide range of head movements.

How do the sizes of vertebrae change along the vertebral column and why?

The sizes of vertebrae increase as you move down the vertebral column. Cervical vertebrae are the smallest, as they only need to support the head. Thoracic vertebrae are larger because they bear more weight and articulate with the ribs. Lumbar vertebrae are the largest and thickest, as they support the most weight from the upper body. This increase in size is necessary to accommodate the increasing load and provide stability to the spine.

What are the four curvatures of the spine and their significance?

The spine has four curvatures: cervical, thoracic, lumbar, and sacral. The cervical curve is in the neck region, the thoracic curve is in the chest region, the lumbar curve is in the lower back, and the sacral curve is in the pelvis. These curvatures give the spine a spring-like quality, providing flexibility and shock absorption. They help distribute mechanical stress during movement and maintain balance.