 Okay, so our stomach, let's check out this lovely thing, this lovely stomach that we're talking about. What do you think this tube right here is? That's actually the esophagus where the esophagus enters the system. So what you'll notice, I don't know, this is kind of an odd way of depicting this, but the stomach has a significant number of a significant amount of smooth muscle, and it actually has three layers of smooth muscle. Let's say three layers. And in the next lecture, we're going to name those layers, of course, and understand like why would you think that we would need three layers of smooth muscle surrounding the stomach? The layers are actually super thick. What's the function? That's one of the functions of the stomach. We've got some mechanical digestion going on in the stomach. The muscles of mastication in your face let your teeth do their job of mechanically breaking down foods. The layers of smooth muscle in the stomach, surrounding the stomach, making up the stomach tube, they allow those layers, allow the mechanical digestion of food to continue in the stomach. It's not the only thing that happens in the stomach. You have chemical digestion as well. In fact, there is super interesting, and we'll talk about this more as well, but there are protein enzymes, and they're called proteases. They're enzymes that break down protein, and they're secreted by the cells in the stomach. And so one of the secretions that is barfed into the lumen of the stomach is this protein digestion, digested protein enzymes. Mucus, holy mucus in the stomach, lots of it. In fact, the mucus is protective of the other thing that is happening in your stomach is acid. In fact, it's hydrochloric acid, and it's an incredibly low pH. It's a super acidic solution of hydrochloric acid that is secreted into your stomach, where if you took a bath in it, it would not be a pleasant experience. That's why when you vomit up your stomach acid, it hurts. That is an unpleasant thing, and it can destroy your teeth if you vomit frequently. The enamel on your teeth can be broken down by the acid, the stomach acid. So barfing is not fun because of the stomach acid, but the stomach acid actually changes the shape of the protein that you eat and allows the proteases to do their job of chemically breaking down some of those proteins. Why does this happen? Why do you do that? Stop it. Let's see. There's a really interesting characteristic of the stomach. I don't know if I would say it's stretchy so much as it's expandable. So on the interior surface of the stomach, there are wrinkles called rugi, R-U-G-A-E, or gastric bulge. And these, like, you can imagine they are, like if you took a plastic bag and you squished it up, there would be a lot of surface area, right, on the inside of the bag, and then if you blew it up, it would remove all those wrinkles, but you could blow up your bag really big. And that's what happens with your stomach. The rugi are these folds in your stomach where it's, like, deflated almost. And then when you have Thanksgiving dinner or your son Kai bakes for you and you have to, like, try a whole bunch of cookie dough and stuff, then your rugi just expands so you can fit more stuff in your stomach. The mechanical digestion happens when those muscles, like, churn the food stuff that you stuck in there. And the more churning that happens, the more mixed up it's going to be, the more it mixes up with the fluids that are being secreted into the stomach and you end up with this gush that then is secreted into this small intestine. And it's allowed to, like, in small amounts, it's allowed to go to the small intestine. The rest of it stays and continues to get mushed up. So let's look at the different areas of the stomach and label these things. So the cardiac region is the area of the stomach where food enters. And it's the first place that you enter. The little, see how there's, like, this, like, bulgy thing? So you enter, food enters into the cardiac region and then there's this little bulge that's almost superior to the entry zone and that, right there, is called the fundus. So that's an area or a region of the stomach itself, the fundus. The body is the bulk of the stomach. So this whole thing is the body. Everything that isn't fundus or pylorus or pyloric region. So the pyloric region of the stomach and the fundus of the stomach and the cardiac region, everything else is the body of the stomach. The pyloric region is just before the pyloric sphincter. And the pyloric sphincter is a significant thickening of the smooth muscle that surrounds the stomach bag, like a super noticeable thickening. In fact, if you palpate the stomach in our cadavers, then like mush, mush, mush, mush, flat, flabby, flabby, flabby. Whoa, holy pyloric sphincter. Like, you can really feel that thing. It's super significant. The pyloric sphincter remains closed. It's a circular arrangement of smooth muscle that can close down and then it opens to let just a little bit of stuff out into the duodenum, duodenum, which is the first portion of the small intestine, and we'll talk about that next. There are a couple of other landmarks that are significant. We have a couple of curvatures. This, okay, here's one curvature and here's another curvature. One of them is the lesser curvature of the stomach and the other one is the greater curvature of the stomach, which one's which? The outer one is the greater curvature. And these are significant because we're actually going to attach other structures to these and to me, it's super clear. The inner one is smaller, a little bit of a sharper curve. It's the lesser curvature. And, did that already? Lumen, greater. How are you feeling about this? Stomach is pretty straightforward. We've got mechanical and chemical digestion happening and now let's go look at the small intestine.