 Now we're going to look at what epithelial tissues do. What are their functions? Like why do we have these things lining a space? And in typical Wendy's style, we must begin with a picture. Ready? First, I'm going to draw you a picture of a human. I'm not even going to make you guess. Because we're in an anatomy class. We'll add some eyeballs on there just for your perspective. Might as well add some limbs on as well. There you are! That's you! Look like you! Perhaps we need some explanation here. So this is a human body. This is, like, okay, highly simplified. Perhaps it looks a little more like a crab. If we were playing Pictionary, I might lose. But let me tell you why I'm going to draw you a picture. Why I am justifying this as a human body. First of all, what is this tube down the middle of you? That's your digestive tube. This is your mouth. I could throw a couple of lips on here, right? Oh, look at that and a smile just for the heck of it. So nice. And if you open your mouth like that, then there's a hole! And there's a hole for food to go down. Check it out. It's all in this tube. This is the lumen of my tube, right? And stuff can travel right on out to the opening on the other end between your legs. That's your anus, dog-pounds. I drew your mouth and your anus on my human. And there it is. Really, anything that is in that tube never is inside you. It's inside you, but it isn't inside you. Like if you had a donut, oh, the donut analogy. If you had a donut and I stuck my finger in the hole of the donut, am I really inside the donut? Not so much. I'm actually whatever. However you want to think about that, this lumen is actually outside of the body. Where are you going to expect to see epithelial tissue? Dude, lining the lumen. Look at my lining. This is epithelial tissue. That makes perfect sense, doesn't it? Where else are you going to see epithelial tissue in my little fantastic drawing? Yes. Oh, that's the worst color I've ever picked ever. This is also lining a space. What is that? It's not that bad. It just wasn't quite as bright as I expected. That's your skin. And then all your guts, all your heart, your lungs, your muscles, everything is all in here. In between, basically it's like you're a tube within a tube. And all of your stuff is in between the tube part of your tube. We can get crazy, but that's like your basic body form. And we can look at the functions of epithelial tissue. I feel like I'm running out of color. How's that possible? By using this little buddy, Crabman, here. We're going to see, okay, what are the functions of epithelium? Well, first of all, what's the function of this epithelium out here? Protection and lots of epithelia function in protection. We're actually going to, in the next section, talk about different types of epithelium. And in that one, we'll see the specific type of epithelium that is really good at protection. And we'll see why the structure enables the function of protection. All right, we also have a couple of things that happen, a couple of functions that happen here. So, first of all, lubrication, really, yeah. Basically, we can secrete stuff. Epithelial cells make stuff. So they can secrete mucus, they can secrete hormones, they can secrete digestive enzymes. They are going to make things sweat. They can secrete sweat. And they just squirt it out. So, secretion is the act of taking, producing substances and, excuse me, barfing them into a space. That's secretion. Makes perfect sense. We also play a role in another really important process, which is absorption. Now, absorption, we think about it and we go, oh, we've got to absorb the ice cream cone that I really wish I was eating right now. That's the cherry on top of my ice cream cone. We've got to absorb all of those nutrients. Sometimes we wish there were parts of the nutrients that we didn't absorb, but, you know, we do. Our bodies are very good at it. Epithelial tissues are very good at absorbing the stuff in the lumen that we need and bringing it into your body so that it can go to the rest of your cells. Because, look, here's Joe's cell sitting in there, starving to death. He needs an ice cream cone like right now. So epithelial cells play a role in that absorption. That's it. So that's where we're going with our functions. And now we're going to look at the different classifications of epithelial tissues and kind of what we're going to see in lab.