 Okay, this is the bells and whistles, the hair accessories section of the lecture, because there are a lot of other things. We've got our layers of our skin and our tissues, but there are a lot of other things that are associated with skin. The most obvious thing associated with skin is hair. Hair is found in a follicle, and there are many things associated with it. So if you check out this hair follicle, hair is like secreted. It's almost like the hair follicle is like a gland, and it's secreting this thing that then we're like, oh, look how pretty and cool it is, but it's like this weird thing. Associated with hair follicles are a couple of super interesting structures. One of them is this thing. This is a gland, and you'll notice it has an opening right here into the hair follicle itself. That thing right there is a sebaceous gland, and we're going to talk about glands, types of glands in the next section, but the sebaceous gland produces a substance called sebum, which I don't know why, but that sounds super gross to me. Sebum is this kind of oily, maybe it is gross, but it's stuff that lubricates the hair and helps it get out of its follicle. Also associated with hair follicle, this one isn't gross at all. This one might be one of my favorite structures ever. This guy, what does it look like? Does it kind of look like a muscle? It is. It's smooth muscle. So it's a structure made out of smooth muscle tissue, and its name is erector, erector pili muscle. So this is an erector pili muscle, and take a thought about what is an erector pili muscle going to do? Muscle tissue shortens, as we know from the last lecture. What would happen if that tissue shortened? What would happen to my hair follicle? So fun. Erector pili muscle is responsible for goose bumps. Because it's smooth muscle, you can't control it. So even though it would be epically cool to totally be like on command, make yourself have goose bumps, make all your hair stand up straight. Dude, that could be awesome. Yeah, you can't do it. You can think of a stimulus that will cause you to get goose bumps. So it's not entirely difficult, but it's not as easy as just like, dude, go. Yes, those are associated with hair follicles. Check this guy out. We actually have sweat glands associated with skin, which makes complete sense. And we have a couple of flavors of sweat glands, and so I am going to tell you, that choice of words is a little bit unfortunate. One of our types of sweat glands is called a marocrine. Marocrine sweat gland. Marocrine sweat glands, that's a marocrine sweat gland. Marocrine sweat glands are the most common sweat glands. They're found all over your skin, and they produce a really thin, watery sweat. When you work out and you're sweating, and like you're getting all drippy wet, that sweat, that real watery sweat, is marocrine sweat. It's produced by these marocrine sweat glands. So it's super watery, and the purpose really is temperature regulation. Sweat makes water on your skin that evaporates and takes heat from your blood with it when it evaporates, and that's how you end up cooling yourself down with these marocrine sweat glands. Marocrine sweat glands don't stink. However, apocrine sweat glands stink like apes, are stinky. I don't know if apes are really stinky. I hope I didn't offend any apes out there. Apocrine sweat glands produce a protein-rich secretion, and nobody's actually sure what the protein-rich secretion functions in. There's some thought that it might be a critter-to-critter communication, and I will tell you why, because really they are stinky sweat glands, and they're found in stinky spots like your armpits. So you have apocrine sweat glands in your armpits that produce this protein-rich substance that is stinky. So we associate it or we've labeled it as stinky. Some of the stink comes from bacteria that eat the protein and then fart, and when they eat that protein-rich secretion and then pass their little stinky gases, we get stinkier than we otherwise would. Other places that are stinky, anus is filled, covered, embedded with apocrine sweat glands. All your pubic region apocrine sweat glands and your nipples apocrine sweat glands, and that's not all. You thought that, oh God, let's stop talking about apocrine sweat glands, but no, earwax, what? Earwax is produced by a specialized apocrine sweat gland, and that one's kind of like, okay, this one's epic. Breast milk. Breast milk is produced by modified apocrine sweat glands. You're making a protein-rich solution that we decided, dude, feed that to a kid that's hungry, so I don't have to like smash up some bugs or something and give it to them. I can just hook them on and like eat the bugs myself and make all this delicious sweat. It's sweat that your children ingested. If you had me for Bio One, you already know that story because it is so unbelievably cool. Okay, I think that everything, I think I've done everything, like doesn't it feel like I've done everything and more? Okay, glands next.