 Here everybody, Dr. O here. Let's talk about the large intestine. So we'll start at the beginning. As you can see there, the ilium, the terminal end of the small intestine attaches at the cecum. So the cecum is a sac-like pouch that receives, is actually hanging underneath the iliocecal valve and it receives whatever is being squirted into it from that ilium. So that's going to be your cecum. It's like the receiving pouch that will then shuttle material through the rest of your large intestine. Another famous part of the cecum, as you can see there, is the appendix or the vermaform appendix. Just so you know, vermaform means worm-like, but I would just call it the appendix. So for years, you know, for a long time, they called the appendix a vestigial organ because it wasn't needed. But we now know, you know, actually research from the 70s was even showing slight disease risk changes with having or not having an appendix. But the appendix is full of lymphoid tissue and these tissues can actually secrete antibodies that help regrow your microbiome after diarrhea or, you know, now in the modern world after using antibiotics. So it does appear to have some immune functions. I kind of look at the appendix and the tonsils the same way. They both part of what's called the reticuloendothelio system that helps mature your immune system and they do have these functions. Doesn't mean you need to risk your life to keep one, but it's also not a vestigial worthless structure, just so you know. All right, so that's going to be the cecum and the appendix. Then we're going to now travel, as you can see here, now we're on the right side of the body going up. We have the ascending colon and then it bends what's called the hepatic flexure because that's where the liver is sitting into the transverse colon that runs across your abdomen. And then we have the left or splenic flexure at the spleen is where it's going to bend again and we have the descending colon. So you have the ascending colon goes up, transverse colon goes across, descending colon goes down. If you have people talking about the hindgut, like you hear about like foregut or hindgut fermentation, all these kind of things, the hindgut is basically going to be the last third of the transverse colon down, but I won't use those terms, but you might hear them, especially with all the discussion we have about the fermentation of fibers and the microbiome and that kind of stuff. So ascending colon, transverse colon, descending colon. Then we have the sigmoid colon. So it's named for its S shaped curve that you see there. And then we go down into the rectum and the anus. So the word rectum means straight. It's the last eight inches of the gastrointestinal tract until we get to those last two or so inches, which is the anal canal. The anus is actually where the anus is going to be where we defecate and how we remove food from our body. So primary functions of all these areas, when I think of the large intestine, the first thing I think of is the reabsorption of water. You produce leaders, maybe 10 liters of digested secretions a day. You need to reabsorb most of those. So the primary function of the large intestine is a reabsorption of water. Obviously it houses our microbiome, which is a topic more for microbiology, but a fascinating topic nonetheless. Then there is going to be some absorption here. Absorption of some of your salts and electrolytes and possibly some of the vitamins produced by that microbiome. Well, let's see here. One thing you don't see here, but there's a couple more features here. They're actually our valves. So there's these folds called rectal valves inside your rectum. The function of those valves is to separate fecal material and gas. That's how someone can fart without any solid material coming out of it. So these valves, their job is to separate the gas and the fecal material. And then at the end, you can't see this, but with defecation, there are two sphincters at the end of the anus. We have an internal anal sphincter and an external anal sphincter. This is very similar to how we micturate or urinate to because the bladder has these same two sphincters. The internal anal sphincter is smooth muscle, means it's involuntary. And the external anal sphincter is voluntary skeletal muscle. So most of the time you have some fecal material in your rectum. You have the urge to defecate. You could defecate, but it's not an emergency. If you reach your points, though, where there's so much pressure in your rectum, that it actually pops open that internal sphincter. So if you've ever reached a point where you're physically having to contract the external sphincter to hold in fecal material, that's what happens when you don't have that smooth muscle sphincter there. So defecation, basically what you have to do is just increase abdominal pressure to force a fecal material out. So that's how those two sphincters, the internal anal sphincter, made of smooth muscle, and the external anal sphincter made of skeletal muscle. That's how they are involved in defecation or preventing defecation. Here just so we talked about with the small intestine and having circular folds and villi and microvilli. There aren't circular folds or villi in the large intestine. But you do have these three structures here. We have the tainia or tiniacoli. These are strings of smooth muscle that contract. And that's what forms the pouches in your large intestine. Those are called haustra. So the large intestine is going to be more wide open and have these big pouches. The pouches are going to be useful in moving material, kind of like an accordion. You want to keep these nice and healthy. If these pouches get weakened, that can lead to conditions like diverticulosis or diverticulitis. Third one on here, epiphylocopenages. Nobody actually knows what they do yet. As you reach the end of the large intestine, the rectum and the anus, you're not going to see these types of smooth muscle. But there are powerful muscles there because clearly they have to contract to help with defecation. So histologically, looking at the lining of the large intestine, the key things here are we have what are called enterocytes, which are going to be the cells in the large intestine that absorb things, primarily water. And you're also going to see goblet cells. Hopefully you've heard that several times now. Goblet cells produce mucus. You need mucus in your large intestine for multiple reasons. Number one, to help lubricate your stool so you're not always constipated. But the mucus can protect from the acidity, right? We talked about with the stomach, how mucus is used to protect from the acidic and viral in the stomach. Well, that's because of your stomach acid. The large intestine can become acidic because of acidic byproducts of the trillions of bacteria living in there. So mucus will form this layer that basically keeps your bacteria and their waste products away from the lining of the intestine. So a nice, healthy mucus layer just as important in the large intestine as it is in the stomach. So this mucus layer, it is what keeps those trillions of bacteria from touching your cells and maybe climbing into your body. So you do want a nice, healthy mucus layer. Now, just from a nutritional standpoint, what's kind of cool here, the colonocytes, these enterocytes in your large intestine, they feed on short-chain fatty acids. So they are designed to eat the fat being produced by some of these microbes. We talk about our good bacteria. Well, they produce short-chain fats that feed these cells. So if you have an unhealthy microbiome, you don't have these bacteria. You could have a real thin mucus layer, and that can lead to all sorts of gastrointestinal problems. But that's for a story for another day. All right, so that's actually it with the large intestine. And so we covered a lot there. I hope this helps. Have a wonderful day. Be blessed.