 Now it's time to classify these connective tissues because if we take different combinations of cells, fibers, and ground substance, then we're going to get a huge variety of connective tissues. So what are these connective tissues? What are the possibilities? Connective tissues fall into three categories. Today, we're going to deal only with connective tissue proper. So I'm going to write that up here, connective tissue proper. This is the one we're going to deal with the most today. But I also want to talk about structural connective tissue. That says structural connective tissue. And we're going to deal with those guys in a whole lab, not that far away, but after our first exam. And then we're going to deal with fluid connective tissue. And the nice thing is how many fluid connective tissues do you think there are? You know what? There's one. It's blood. Blood is a bloody connective tissue. It's matrix fibers and ground substance. It's just super watery. It's way, the matrix is way more watery than say the matrix in adipose tissue or bone tissue or cartilage or a realer connective tissue. It's just fluid. So let's look at connective tissue proper. I hope I don't run out of room here in my little diagram. What do you think? Am I going to? I'm going to include the whole thing. Watch. There are two types of connective tissue proper and they are dense and loose. That's pretty straightforward. Dense connective tissues just have the fibers all tightly lined up and not necessarily organized but just stuck all together. The loose connective tissues, the fibers are just kind of floopy all over the place because floopy is a word. Really, dense connective tissues come in two flavors, regular and irregular. So far, so good. That's it. I was expecting to have to go down farther. So we only have two options for our dense connective tissues. The fibers tend to be really thick and close together but in a dense regular connective tissue, they're all lined up and going the same way. In dense irregular connective tissue, it looks like my house, my room. All my stuff is just like in this pile that's super unorganized. If you go to my mom's house where I am right now, I feel like I'm in dense regular connective tissue right now because everything is like really organized and it's all in a nice little package. She's doing all my laundry and folding things up. If I do my laundry, I feel like dense irregular connective tissue. She's making my laundry regular. Thanks, mom. Loose connective tissue has three flavors. Are you ready? I'm going to make my loose connective tissue flavors go this way. Are you following what I'm doing here? There are my three flavors. That way I can fit them on here. Three types of loose connective tissue, one of them is adipose. Adipose tissue is fantastic. It might be, did I already say this? My favorite tissue ever. It has, unfortunately, I don't love it on me, but it sure is cool to look at in your slides. It's basically a cell, a giant cell that literally looks like, dude, that thing, that's an empty cell. Nobody's home. And if you get the right section, you get a tiny, tiny little nucleus. And if you are lucky, you might see a tiny, tiny bit of cytoplasm. Really, what's the rest of this stuff? Yeah, my friend, it's what you would think in a fat cell. It's a blob of fat. Look at this. It's a huge, lipid blob of fat adipose tissue. So you're going to see something that's like huge and empty. It's not really empty. It's storing all your extra energy. Thank you very much. But they're really, really distinctive. Okay, I got distracted. Adipose tissue is one. We also have a tissue called aryler. The aryler connective tissue is loose, although some of your slides might make it look dense. But it looks like tiddlywinks. It looks like you dropped a whole bunch of toothpicks. And then there's like stuff that's spread out. It looks kind of dense. But you can imagine just sticking your finger in there and mixing it around. It's going to go every which way. It's going to be super messy and easy to move. So it is really a loose connective tissue. And it's the packing peanuts of your whole body. Your adipose tissue stores energy and it provides cushioning. That's handy. But aryler connective tissue like is found all over. In fact, when you skin a chicken leg, when it's raw, and you peel off the skin and that kind of like webby, whitish stuff, that's aryler connective tissue. When you come into lab, we can probably find some aryler connective tissue in our cadavers that we can look at so that you can kind of appreciate the net-like webbiness. And it's found all over the place. It's kind of like I've heard it called the packing peanuts of the body because it just kind of keeps everything connected together so we don't wiggle around and have lots of friction but also nicely organized. Not very heavy, not very expensive to make. Last one. Reticular. Reticular connective tissue is made out of and it's found in solid organs. And those solid organs are things like lymph nodes or the spleen. We're not actually going to see it in lab, but we do need to learn about it. I'm going to fill out your structural connective tissue box here because we're going to get really comfortable with it now. We're not looking at any of these in detail right now. We're going to look at all of them later on down the road, but our structural connective tissues come in two flavors. What do you think? Go ahead and guess before I start writing them down. Bone and cartilage. Those are our two flavors of structural connective tissue. Again, we'll have a whole day on the histology of bone and cartilage. Bone comes in two flavors. We have compact bone or dense bone and we have spongy bone. Spongy bone has like 32 names. It's called cancelous bone or trabecular bone. I think spongy is the easiest to remember. So that's what I go with. Cartilage comes in three flavors. Cartilage, we have hyaline cartilage. Again, I'm going to do that little thing where I go down this way so I can fit them all. We also have fibrocartilage and we have elastic cartilage. Again, we're going to talk about these guys in detail later on and we'll look at them. We'll look at different examples and you'll have to identify all of them, but we're just not going to do it today. I want you to have the whole picture so that when we get there, it'll be easy to just plug in our information because all connective tissues have this in common. Let's do the next thing. It says connective tissue histology. I wonder why I'm doing that. Probably shouldn't say that out loud on the video, but I did. So I'm going to go figure out why we're doing connective tissue histology. Maybe we're going to go look at University of Michigan. I'll be right back.