 Hi everybody, Dr. O here. In this video, we're going to introduce the digestive system. This is a critically important system because all systems are interconnected and all are very important. But the digestive system, the health of your digestive system basically determines the health of the rest of your body. That's what I believe. That's what apocrates believed hundreds of years ago, right? So in this video, we're just going to talk about the basics of the digestive system. But just a big picture, what does it do, right? The digestive system is what allows us to take our food and break it down and digest it into a small enough piece so that it can be absorbed and then we absorb it into our bloodstream into our lymphatic system and then carry it through our body. And then we eliminate what we can't use. So really the three steps of the digestive process, if you want to look at it that way, would be the digestion, the absorption and the elimination. Then once these things are absorbed into our body, that's where your metabolism takes over. It takes these building blocks that you've broken down from your food and extracts energy from them. So now we have energy to do work and we have the raw materials we need to do it. So when people say like you are what you eat, that's absolutely true. Whatever you had for breakfast is going to be broken down and the carbohydrates and the amino acids and the fats that are in that meal will become signaling molecules in your body, muscle on your thigh, these types of things. So digestion is what allows us to take this chemical energy, the food that we have around us and break it down in a way where we can take it in and use it. So very, very important that on a whole another level, which we talk about in microbiology, your gut is also the home of the majority of your microbiome. So the ecosystem that you are is built around this relationship between you and your gut microbiome. So we won't talk about that a lot here. That's a topic for microbiology, but it is just fascinating. I think that's probably part of the reason why your gut health is so closely related to your mental health, neurological health, et cetera, et cetera. So this is really cool stuff. All right. So I mentioned the three phases we're going to talk about here, digestion, absorption, elimination. There's going to be videos that talk about all three of those things. Just the system itself, we have the GI tract or the gastrointestinal tract. You're also going to see it called the alimentary canal, but I don't use that very often. It's basically, if you look from your mouth to your anus, it's about a 25 foot tube. It would be 35 feet if you were to unfold it. If there wasn't, there's all the folds and crevices caused by smooth muscle contraction. If you eliminate that, it would actually be 35 feet long, but 25 feet is a nice safe number. One other thing I find really fascinating, kind of hard to wrap your head around, but your gastrointestinal tract is outside your body because the mouth and the anus are both exposed to the external environment. Your gastrointestinal tract really needs to be looked at like a tube that's running through your body. But the contents in your gut, like the fecal material and the gut microbes that are inside of you, they're not technically inside your body, they're running through your body in a hollow tube. Kind of like if you're on a train going through a tunnel in a mountain, you're not in the mountain, right? You're running through the mountain. So I know that's kind of a strange way to look at it, but it is very important because it explains why your digestive glands are exocrine glands. We'll talk about that. It also explains why a massive portion of your immune system is linked to your gut because there are trillions of bacteria and viruses and fungi and all sorts of creatures living inside your gut right now, which is an external surface of your body, and your immune system is monitoring that to make sure they don't get in, right? So I think that is worth noting there. So the first time that food is actually in your body, if you want to look at it this way, is once it's been digested and absorbed into your bloodstream. So that's kind of interesting. Our one last thing is to get out of the way with this introduction before we start diving in deeper. I mentioned this digestion, absorption, elimination. Digestion is definitely the most complicated. So I'm going to run through the different, the six steps involved in digestion. First is just ingestion, right? Deciding what to put in your mouth, deciding what to eat, taking it into your oral cavity. And then we have, I'm breaking it up and all of that, but then propulsion. Moving the food you eat from one organ to the next. So moving the food like from your mouth here to your pharynx, to your esophagus, to your stomach, et cetera. And then we'll also talk about the different names of food as it travels through you that way. And then we do have just the mechanical digestion. So really digestion can be both mechanical and chemical. So mechanical digestion is going to be the mixing and churning and breaking down of food, whether that's your teeth grinding it, your tongue mashing it, or your stomach churning it up. That would be mechanical or physical digestion. Then we have the really important stuff, the chemical digestion. And the huge majority of that occurs in your small intestine, specifically the jejunum. But we'll cover all that. The small intestine uses enzymes to break the food that you eat down. So to break the starch that you ate from your pasta or whatever down to individual glucosis, or to break the protein in the steak you ate down to individual amino acids, or to break your fats down as well. So that's going to be the chemical digestion. And that's the really critical important step because if you don't chemically digest your food into these really small subunits, they can't be absorbed. So that is the next step. Then we would go into that absorption and then whatever can't be absorbed, like the fiber you eat and other things, would be defecated. So I think that's a deeper dive into the actual steps we're going to look at here. Okay. That is a pretty solid introduction to the digestive system. I hope this helps. Have a wonderful day. Be blessed.