 We're going to look at the spinal cord, but I want you to remember, I'm going to draw you a picture of a slice of spinal cord, a transverse section of a piece of spinal cord. But it is a cord, and it travels from your sacrum all the way up to your brainstem, and it travels through the trans... I mean the vertebral foramina of your individual vertebra. This cord, if we sliced it at any level, we're going to actually see a similar picture. I have this visual here for you, just so you can appreciate the fact that I'm going to draw this little butterfly for you, and we're going to label parts, but that butterfly, no matter where I take my slice, that butterfly is going to be there. And these little spinal nerves that are coming off of the spinal cord, those are going to be there as well. Are you ready? Don't forget. It's three-dimensional that we're taking a slice of. Let's slice. You may think, dude, when is a rock star? She gave us a picture of a spinal cord to label on our lecture notes. I am not a rock star. I mean, I totally am a rock star, but you have to draw that yourself. In fact, on your exam, quiz, quiz number one of nervous system fun times, that's one of your tasks. You're going to have to draw the spinal cord on the back of the quiz sheet, so get comfortable. When I draw my spinal cord, I start with those two little twanging-like ear things. Of course, little ear things, right? And, you know, there's kind of a line that connects them. There's a hole in the middle. I guess what that thing's called. I love it when Anatomy's easy. That's the central canal. There are two little bloopies on the side that may or may not be there. There are two little legs that are there. And all of this that I just drew, I'm going to put a tiny little star right here, because all of that stuff that I just drew is gray matter. Now, that means that everything else that I'm going to draw right now, like this and this, all of that, that's all white matter. What the heck is the difference between gray matter and white matter? Oh, let me tell you, white matter is mostly myelinated axons. That's what's making up most of this white matter tissue. And so myelin, myelinated axons, remember that myelin was that fatty covering over the axons that formed those kind of bubbly things that was like insulation. So what you'll actually see in the white matter, I'm going to make my myelin like kind of orangey or yellowy. Yeah, that's good. Here's a little bubble of myelin. Kind of looks like a little cinnamon roll. And no, I'm not hungry. And there's a little dot in the middle of it. What's the dot? That's the axon dogs. The axon is this tiny little dot in the middle. The myelin is that lovely orange circle, cinnamon roll, surrounding it. We'll see in a second why it looks like a cinnamon roll. Most of the white matter is made up of axons. If you catch a cross section of an axon, what does that mean about that neuron? Where's it going? Up or down. It's either going up to the brain or it's coming back down to go deliver messages. What are interneurons? Now, gray matter. What is gray matter? It's mostly cell bodies. And I'm going to show you in a second whose cell bodies we're talking about. But first, I'm going to finish drawing my picture for you. I'm feeling a little sad, a little cramped right now. You know, I'm going to have to squeeze some stuff in here. Look, I actually am connecting. Oh my gosh, I'm never going to fit it. We're going to have to scoot on over to fit it. Know that the same thing is happening on the other side. Now this looks like it has to connect here. This has to come down here. Fantastic. Okay, do you see how I connected them? The plot thickens. And now I've got a little weenie pathway that goes off this way. And then I've got a big old pathway that goes this way. Okay, let's label our parts. And then we'll kind of orient ourselves. First of all, let's look at what's going on with the gray matter. We have A. I'm going to label them on this side. What a great idea. This is the anterior gray horn. This looks like a horn, doesn't it, or a butterfly wing. This is the lateral gray horn. Some sections of spinal cord do not have a lateral gray horn. This is a posterior what? Gray horn might as well do my central canal while we're here. The posterior gray horn does its thing and becomes a posterior root. This is a posterior root. And guess what this little blobby thing is that is not down here. This looks like one of those, oh gosh, I'm going to come up with this analogy for you. It may or may not do anything for you. One of those things in like oak trees that where all of a sudden an oak tree starts getting these big old blister looking things, like the wood actually blisters out because I think there's wasps in there or something. That's what this looks like to me. But it isn't that there are no wasps in there. This is called the dorsal, I mean posterior. You can call it dorsal though. Root ganglion. That actually tells you like nine million things right there. Here's the root. It's a ganglion, which means what's in there? Dudes and doodesses of a feather. That means there's cell bodies in there, right? A bundle of cell bodies in the peripheral nervous system is called a ganglion. Does that make you like kind of excited? I love the pieces together, I love it. So the posterior root ganglion is in there and does anybody remember what color I used for my cell bodies? I better stop drawing them or else I'm not going to be able to fit anything else in here. I can't help it. I have to draw them in. Look, they're going out that direction. I mean, they're bringing information in. I should not have drawn it like that. I should draw it like that and go out here to a whole bunch of sensory dendrites. Look, it's a sensory neuron. And the sensory information comes in through these structures and to the cell body in a posterior root ganglion. What? For real. It's true story. All right, let's label some more parts. We have a really important part right here. What this is that our fibers are passing through, this is my spinal nerve. Is it in the central nervous system or the peripheral nervous system? It's a nerve, dogs, it's in the peripheral nervous system. That means that only stuff in here is included in the central nervous system. All of this stuff is peripheral. Who else is traveling through this? Well, who does this look like? I know it's going to be so exciting to put these pieces together. What? True story. What color is that? Who's being innervated? This is a somatic motor neuron. And it's actually traveling through my spinal nerve as well. The somatic motor cell bodies are found in the anterior gray horn mostly. And what do you notice about the spinal nerve? It contains fibers from both places. Now, we have two more structures that I want to label here. You notice that I split us off. I split off this buddy and this buddy. And these guys are Ramai. This is my posterior ramus. And fibers that are traveling through there are innervating the muscles and stuff going on on your back. And the sensory fibers that come in are from your back. So look how tiny that thing is. Who cares about your back? I mean, let's just not think about that anymore. I mean, I guess we do care. But we have more stuff going through our anterior ramus. It's just a branch of the spinal nerve. The anterior ramus is carrying all the information to anterior body parts and guts. Are there any other structures that I need to label for you? You know, I think that this is relevant. We didn't really label structures in the white matter. But the fact is there are structures in there. And you have like columns or finiculi. This is a finiculus, finiculus, and there's multiple finiculi. And these are basically giant paths, groups, tracts. They're tracts of axons that are traveling up and down, sending information up and down to this spinal cord. So I bring chocolate to lecture and lab on the day that we do this topic. I think so. You're getting a lot of information right now. But that's your spinal cord. I think that's everything that you need to know. Now let's look at the anatomy of a nerve itself.