 Okay, let's build some connective tissues. What were the components of our connective tissue? Remember, go ahead and think back in your brain and write down the three ingredients that you need to make a connective tissue. We're going to need some cells, right? We're going to need some fibers, right? And then we're going to need some ground substance. And this is because connective tissues are cells in a matrix of fibers and ground substance. What kind of cells can we possibly find in connective tissue? Lots and lots of options. So let's talk about some of the more common. There's a cell that we're going to see often, especially when we're talking about our other connective tissues like bone and blood. We're going to see these cells called mesenchymal cells. Comal cells. I'm not going to write the word cell down because if it's in the cell pile, it's a cell. Mesenchymal cells are stem cells. And so these guys give rise to all sorts of other types of cells that you can find in connective tissue. Another type of cell that you will find quite commonly is called a fibroblast. Fibroblasts are specialized cells that actually build fibers. So guess what? Check it out. Our friend, the fibroblast, is basically going to barf out a bunch of fibers into the surrounding environment and produce the fibers of the connective tissue. So fibroblasts are actually building the fibers. I remember that, blasts, build stuff, and we're going to see that again, especially when we talk about bone. We're going to see other blasts that are building stuff. That makes it a little bit easier to remember. We also have different kinds of connective tissues, have different kinds of cells. There are cells called adipocytes. These guys are only found in adipose tissue, which is fat, and we'll see them of all of our tissues that we're going to learn. I think adipose tissue might be my favorite. We see it everywhere in almost every single histology task that we have. There is, if we're looking at an actual organ or an actual structure in the body, we will be able to find adipose tissue in almost everything. So these guys are kind of fun. We'll look at them in a little more detail. Then you have a whole bunch of immune cells, and these guys basically patrol the connective tissue. And you, I don't know, it'd be interesting to find out, like, what are you made of mostly? I would think they're, I don't know, muscle tissue. I would argue that you are more connective tissue than any other kind of tissue type. But I'd be really curious. The one that I would think might be close is muscle tissue. There might be more muscle tissue in the body. Somebody go look that up and tell me, or somebody in YouTube land post a comment, because I'm really curious about that. Hmm, what is the most common tissue type in the human body? The immune cells that we're talking about, they're going to include macrophages, mast cells, that says mast, and somebody else, and various lymphocytes. Okay, so basically a whole bunch of immune cells that come in and are patrolling the area to make sure that everything is cool. Is this it? Is that the only kind of cells that you're going to find? Absolutely not. And when we look at specific kinds of connective tissue, we will look at other possibilities as well. Fibers. Here's your menu of cell types, and you can throw in whatever you want to make your connective tissue. There are three possible fibers that we can use. First of all, there are collagen fibers. Collagen fibers are big, rope-like fibers that are super strong, wholly strong, but they're not very stretchy. So collagen is strong, not stretchy. So that collagen fibers for their diameter or size, whatever, they're stronger than steel, very cool. You also have fibers called reticular fibers, and this is going to make you mad. This word is going to make you mad. So burn into your sweet, precious, brilliant little brains right now that there is a type of fiber called a reticular fiber, and in Achillea, it's actually made of collagen. What? So you have collagen fibers, which are big, thick, strong ropes of collagen, which is nothing more than a protein. And then you have reticular fibers, which are thin, like kind of bouncy, like a bouncy ball. You can use reticular fibers to make bouncy balls, or lymph nodes, you choose. But they're also made of collagen, so collagen is just a little bit, what's the word? Dinner. That was the word. Then you have elastic fibers. Elastic fibers are what? Holi stretchy, they're the stretchy little fun fibers, and they're made of a protein called elastin. They're really fun to see in a slide, because they're really distinctive. They're like worms, like long, thin, dark worms that are different, the collagen fibers. Sometimes the collagen fibers are so big and thick that you don't even realize that you're looking at a fiber. You just think that that's the background, but it actually is a collagen fiber. So, okay, so those are our three fiber choices on the menu tonight. Now, shall we add in some, I think we're gonna go for some pink ground substance. The ground substance is what everything is floating in. Can you imagine that? It's like the cup, and we have fibers, which could be the spaghetti in the cup, and wait a minute, the ground substance isn't the cup. The ground substance is like the fluid in the cup. Top ramen. You have a cup of top ramen, and the brothy broth is the ground substance, and then the noodles are the fibers, and then because you are smart and you want to eat your vegetables, you're gonna throw in some chopped up carrots. Those are yourselves. You just made a ground substance for dinner. Fantastic. Ground substance is mostly made of water. That's the broth. But is the broth like nothing but water? No, it has some stuff in it. So it has solutes in it, flavoring. I'm gonna give you some names of solutes, and we're going to see why we care about these when we get to cartilage. But proteoglycans, I'm not even gonna write them down, because we'll write them down when we get to cartilage. Proteoglycans and glycosaminoglycans are really hydrophilic substances that are found in the ground substance in cartilage, which is really fantastic. And that helps, and they're found in lesser amounts in other connective tissues. And because these solutes are so hydrophilic, they love water, they suck water into your connective tissues and keep you nice and hydrated. That was me trying to say hydrated and bloated at the same time. I was trying to think of, hmm, I wonder if those solutes are responsible for lotion. That's a word. You guys, where's my matrix? I'm just gonna throw this out here right now. If we add these two together, that's my matrix. Do you wanna look at how we classify different connective tissues? Because here they are, these are all of our possibilities. And then, if you throw in a whole bunch of collagen fibers, you're gonna get one kind of connective tissue. If you throw in a whole bunch of elastic fibers, it's gonna have a different characteristic entirely. So you can imagine how we can fiddle with these things and we can make a great diversity of connective tissues. So let's see what kind of connective tissues we can make. Great idea.