 These cutaneous membranes are actually super similar to our other membranes. They consist of an epithelial tissue attached to a connective tissue via a basement membrane. And interestingly, the epithelial tissue layer is known as the epidermis. And y'all know that already, right? Whoa, what? Stop. That's a bit of flair. The epidermis is made of what kind of epithelium do you think? Hopefully, that's not a hard question to answer. Of course, it's stratified squamous epithelial tissue because stratified squamous epithelium is thick, lots of layers, the layers on the top are flat. Think about your skin. You can like do some pretty serious abrasions and not get through to the connective tissue layer where you have blood. And if you do break through to that layer, what's that layer called? The dermis. And there are a couple of types of connective tissues that we're going to find in the dermis. There are five layers in the epidermis and there are two layers that we're going to know in the dermis. So to say that we're done with layers, if you know epidermis and dermis, yeah, it was a good effort, not quite. We're going to look at all of that. Don't forget that we do have a basement membrane that connects these two things. And the epidermis, the stratified squamous epithelium, but it's also, it has an adjective describing it. It's keratinized, keratinized. And we're going to look at keratin. We're going to talk about, you know, what distinguishes the different layers in the skin and the presence of this protein called keratin is a really significant characteristic. Skin, because of the keratin, skin is, it has some important functions. First of all, it's waterproof. Think about that. Do you want your skin to absorb water? I mean, think about what would happen if you took a shower if you actually absorbed water through your skin. I'm just going to leave it at that and try really hard not to expand. Everybody pat your skin and say thank you for being waterproof. It's because of the keratin that it's waterproof. That waterproofness is about protection and your skin is absolutely protective. Your skin also plays a role in thermoregulation in maintaining your body temperature. Think about if you get hot, your skin flushes, it turns red, and really that's about blood vessels in the dermis vasodilating to get more blood closer to the surface of your body so that it can cool off next to air as opposed to, you know, maintaining 98.6 or whatever the homeostatic temperature is in your body. So, skin also has sweat glands which participate in thermoregulation. Skin plays a role in calcium homeostasis via vitamin D. Vitamin D is a molecule that your skin actually produces when exposed to sunshine and vitamin D helps. It's like a hormone or a signaling molecule in your body and it actually helps you absorb more calcium. And then there's one more thing, one more, ah, ah, this is an important one. Dude, skin tells you about your environment. Ew, I just evoked like, what kind of information could my skin give me right now that I wouldn't like? Like if there was like some little critter that decided to crawl on my neck. My skin would communicate that, like it would pick up that sensory information and then I'd be like, yeah, bye-bye little critter, get off my neck. I don't know, that was the worst idea I've ever heard of. So, yeah, skin plays an important sensory role. Now I'm going to go shake out my clothes and make sure there's no critters on me and then we're coming back to talk about the layers of your skin.