 Cartilage, we know it's a connective tissue. What's it made out of? What are the cells that are actually found in the cartilage? Well, since you asked, I guess I'll tell you. First of all, who would you guess? Go ahead and take a wild guess. Think about connective tissue and think, okay, who is one of our connective tissue cells that is going to be present in cartilage? I'm going to give you a hint. Ms. Misankable cells. I'm not going to continue that little adventure. Misankable cells, familiar. These guys are our stem cells for almost all types of connective tissue. So they will give rise to other connective tissue cells. Awesome. In our other connective tissues, what did they turn into? Do you remember? Misankamals gave rise to fibroblasts. Guess what? There are fibroblasts in cartilage, but they have a special name. Of course, because don't you need 30 names for every single structure that we learn in anatomy? They are called chondroblasts. Chondroblasts. And here's the scoop. Chondroblasts are fibroblasts. These guys are producing, I'll make it purple. They are producing, okay, no, we're going to go like this. They're producing the ground substance and the fibers in your cartilage tissue. They're making the matrix. They make the whole thing. Because they're found in cartilage and they're specifically making cartilage, they aren't called fibroblasts. They're called chondroblasts because they're producing cartilage. Chondroblasts, how crazy is this? What do you think about it? Cartilage, it's kind of a bouncy tissue. It's not hard like bone, but it certainly isn't fluid like blood. So it's kind of this in between like trampoline tissue. If you jumped on it, you would get some bounce going on. So a single cell, like a little chondroblast, it's just chilling in the matrix, like building fibers, barfing them out, barfing out fluid and solutes and stuff surrounding them. These little guys literally get painted into a corner. How? Well, it's almost like they're building a little like, they're building, they're like barfing out concrete except it's squishy concrete all around themselves. And pretty soon, what's going to be true? They put out all these ground substance, all these fibers all around themselves, and pretty soon they're going to be trapped. I'm going to tell you this now because it's interesting, but a chondroblast builds ground tissue and substance all around itself, but they're not idiots most of the time. And they actually make, like they build, this is my chondroblast right there. Here's my chondroblast's little nucleus right here. They actually build the ground substance around themselves, and they leave themselves a little space to live in. They paint themselves into a corner, but they leave enough unpainted ground that they are not going to die. And that space has a name, and I don't know why, but I love this. It's a space called a lacuna. So the cartilage cells live inside these little homes called lacuna. Now here's the interesting thing. The chondroblast is building the fiber matrix madness around itself once the chondroblast is trapped in its lacuna. It's not a chondroblast anymore. Do you know what it becomes? It becomes what everybody wants to become. Don't you want to become a chondrocyte? That says chondrocyte. Everybody wants to be the chondrocyte. The chondrocyte is no longer blast building things. The chondrocyte is chilling in this awesome little house it built for itself. It's lacuna matata. What a wonderful day. It's just hanging out in this little house and loving life because it's nice and safe and it doesn't have to work anymore. That's cool. We have mesenchymal cells that become chondroblasts that build the matrix and become chondrocytes like when they retire and they're ready to just hang out and chill. The ground substance that chondroblasts are barfing out is filled with solutes. And I'll tell you right now, these solutes are very hydrophilic. What's that mean? They love water. You know, they don't just like it. They love it. Water is awesome and they like suck water into themselves which makes complete sense. The more hydrophilic solutes you have in a space, the more water you're going to draw in. This is relevant because I'm going to write this down right now because it's really important, but this is kind of going to blow your mind a little bit. Are you ready to have your mind blown? We know that epithelial tissue is avascular. We know that connective tissue is vascular, usually highly vascular, lots of blood running through your connective tissue. Cartilage is the exception. Cartilage is avascular. What? Yeah, true story. It's the only... Are there any exceptions? I don't know. It's the only connective tissue that does not have a blood supply going through it. So why does it matter that all the solutes in the ground substance are hydrophilic? Because our little chondroblasts and chondrocytes, these guys, the only way they can get food and garbage pickup is if diffusion happens. So if there's no fluid in the matrix, if it's dry cartilage or dehydrated cartilage because you didn't drink your water, then those little guys, those little cells, those chondrocytes chilling in their lacuna are not going to have any food and they're going to die and your cartilage is going to be sick, unhealthy cartilage. What? Because the cells rely on diffusion for food and garbage pickup. Everybody else gets to have special delivery right to their house from the capillary. That's how the food and nutrients get there and that's how the waste gets picked up through the blood supply. If you are a vascular, you don't have blood. If you don't have blood, you better have some other strategy for dealing with your garbage. There are three kinds of cartilage that we're going to look at and our three different kinds of cartilage are based on the fibers that we're going to find there. The whole cartilage has collagen fibers. In the case of hyaline cartilage, the collagen fibers are there but they're tiny. They're almost invisible little fibers and so the hyaline cartilage looks really glassy and clear. The matrix looks clear. You can see the big bubbly lacuna and then it looks like you can't see big old fibers running through it. Some cartilage has elastic fibers. What kind of cartilage do you think that would be? Elastic cartilage. Don't you love it when it's like that? How easy is that? If you see those little thin, glassy, break-shattery looking fibers running through your cartilage, then you know that you have elastic cartilage. My last kind of cartilage is called fibrocartilage and fibrocartilage has big, thick collagen fibers in it. And so the fibrocartilage is like, it's super tough. The collagen, you can see it. It looks kind of wavy and it just looks thick. And it has a different function, right? A fibrocartilage, fibrocartilage is found in places where grinding takes place, like the menisci in your knee, between the bones in your knee joint. They're separated by fibrocartilage pads called meniscus side, menisci. Two menisci, one on each side. The intervertebral discs, so the cartilage pads between your vertebrae, those are made of fibrocartilage. The elastic cartilage is found like in your ear pinna and that, you know, it kind of makes sense, right? That seems kind of elastic-y. Like you need elastic fibers in order to be able to twiddle your ears because I know you're twiddling your ears right now. Knock it off. Quit twiddling your ears. And then the hyaline cartilage is found on the tips of all long bones, which we're going to talk about next time. And we can find it in other places. Like, remember when we looked in the trachea and we're like, ooh, what's that really cool-looking tissue? That was hyaline cartilage. It's found in the sea rings and the trachea. All right, you have a view of cartilage. Now let's talk about our different kinds of bone tissue.