Today we are talking about the digestive system and how we can help our digestive system function optimally through some yoga and mindfulness exercises. So we're going to start off. I just want to make sure everybody understands how important and vital our entire digestive system really is in keeping us healthy. The main components of today's lecture. We're going to go through what the digestive system really does, what are ways that we can help keep ourselves healthy, keep our digestive system functioning as the best of its ability, and how this can really impact our health overall and long-term. So we talk about the digestive system, we're talking about a long tube that actually goes all the way from our mouth to our anus. So one thing that's really interesting to keep in mind is that, our digestive system, until all of the nutrients and everything we're eating is absorbed, it's really outside of our body cell. So what we're actually doing is we're taking food and components from the outside environment, we're moving it through our bodies and we're allowing certain things to be absorbed. In addition, our digestive system is going to be aided by a lot of different secondary organs that you probably have heard of that are on the screen in this picture such as the gallbladder, and the liver and even the pancreas. In addition, the digestive system is going to have an important immune function too because it's going to allow us to have proper microbiome, proper bacteria living in our gut that is in a symbiotic or helpful relationship, and it's also going to keep out bacteria and other types of organisms that are harmful to our bodies. So when we talk about digestion, it's really important to keep a couple of things in mind. One of the most important things that digestion does, is that it allows nutrients and water to be absorbed into the body or into the bloodstream. It's the entire tract itself is going to be lined by different types of cells. Epithelial cells are one type of the general four types of tissue in the body. The other three being connective, muscle and nervous. The epithelial cells are categorized by shape, columnar, cuboidal squamous and layering. In general, their role in the digestive system is secretion, absorption and protection. Varying types of epithelial align the entire GI track. The goblet cell is a specialized type of epithelial cell that is able to secrete protective mucus along the intestines. One of the biggest parts where yoga really comes into this is that movement is crucial for proper digestion. So skeletal muscle movement is going to support digestion but also actually twisting and movement of the internal organs and cells. The two things that are going to help break down all of our foods into useful macro-molecules or useful material, is both mechanical digestion, which is movement. It can be chewing, but it also can be twisting. It can be running, it can be exercise and then chemical digestion which we're going to see with lots of different enzymes that are going to help break down different types of molecules or food substances. Okay. So digestion is always going to start in the mouth. The process of digestion as it moves from the mouth to be excreted from the body can be broken down into two general categories; mechanical and chemical digestion. Mechanical digestion has to do with physical movement that help break the food down into particles. This starts in the mouth with chewing and continues throughout the digestive track via peristalsis. Chemical digestion also occurs in all locations of the digestive tract. Starting in the mouth, where enzymes like salivary amylase in the saliva helps break down molecules. There are additional enzymes that will break down food throughout, such as [inaudible] in the stomach, and enzyme secreted by secondary organs into the intestines. The epiglottis is a great example of the use of muscles and tissues to compartmentalize the GI tract and separate the digestive organs. In this case, the epiglottis is able to prevent the food from moving into the windpipe. So from the mouth to the esophagus, we'll see another part again between the esophagus and the stomach, and then before the stomach and the small intestine and it's actually made of smooth muscle. As this smooth muscle contracts, it helps to move or protect the movement of the food by contracting which aids in allowing further digestion. Interestingly enough, we have control over this and we have control over keeping these components healthy. So things like exercise, movement, putting our heads upside down, coming back up, these are all things that help to stimulate smooth muscle contraction throughout our GI tract. So what you're looking at right now is a picture of the stomach, and what you can see is that it connects to the esophagus. We have a smooth muscle sphincter that's going to protect food or prevent back-flow from the stomach to the esophagus. So what actually does the stomach do? I think a lot of us are always sort of referring to it in general, and I think it's important to get a pretty good understanding of the function of the stomach. So if you were to imagine eating a piece of food, a bite of a sandwich, you can imagine chewing, as we all do, and then swallowing. The chewing of course in the mouth as we mentioned, helps you start to break down some of the food and mixes with saliva, carbohydrates are to be broken down and the food is brought through smooth muscle contraction into your stomach. Then stomach is actually going to take that food and it's going to process it more. So smooth muscle contraction aided by skeletal muscle contraction, when we move our bodies, when we do twisting postures and yoga, and these are all going to start to mechanically digest the food even more. Of course mechanical digestion is always going to be aided by chemical digestion. Chemical digestion in this case in our stomach is just breaking down proteins. This is really interesting because I think, a lot of times we think stomach is breaking down all of the food components. But it's really not. We have a variety of enzymes in all of our digestive track organs and secondary organs such as peptidase which breaks down the proteins in our stomach. In addition, the stomach has a really important role where it also is able to protect us. So we have acid, which we all probably intuitively know because at some point you've probably eaten something and feel a little bit of acid re-flux. Acid re-flux is the experience of acid building up in the stomach that starts to move back up into the esophagus. So that acid is actually created in our stomach by important cells and it plays a crucial role. Not only does it make all of our enzymes active so they can break down the food, it also protects against infection and bacteria. Right. That hydrochloric acid is very acidic, it's a very low pH. In fact, it would burn your skin a lot if you actually had it poured on your skin. So we keep it isolated in the stomach but it's so valuable for our immune system and the functioning of our stomach overall. Now one thing I just wanted to mention that is often lost with things at the stomach does, is it also helps with B12 absorption and therefore, red blood cell production. So when we talk about the stomach, were not even just talking about digestion, we're also talking about the ability for our bodies to make enough red blood cells and make healthy red blood cells. Okay. So once that food that you just started to digest in your mouth and your stomach, that bite of your sandwich is going to continue to travel into your small intestine. The small intestine is where we start to see this highly convoluted or this highly folded area of our digestive system that's going to continue to break down foods. So that sandwich that you ate, you're going to have molecules that are going to start to be broken down or completed broken down such as lipids and carbohydrates. They're also most crucially going to be absorbed. Right? Because as I said in the beginning, we don't consider that bite of sandwich to be inside our bodies until it's absorbed into our bloodstream from our digestive track. So now we have to get it in. So the interesting thing about the small intestine is that we have these large folds, but then if we zoom in on the molecular level, there's all of these micro folds too and what this is doing, is it's increasing the surface area or the amount of small intestine we have. So after the food that we're still digesting moves from our small intestine into our large intestine, we're going to switch gears a little bit. The large intestine also has all of these folds. But it is larger and it doesn't have as many convoluted folds as we saw in the small intestine. So the large intestine has similar function. We're going to be absorbing nutrients. For the most part, digestion is pretty much complete by the time we get here. The other important thing that the large intestine does is it absorbs a lot of water. So remember the whole time you're eating your sandwich, you are also drinking water and hopefully we're all staying hydrated throughout the day. So this large intestine is also responsible for taking in a bunch of nutrients as well as absorbing all of the water and making sure we have enough water in our bloodstream. Now, looking at the shape, you can tell that to actually move through the large intestine, we need movement to help do this, right? So a stagnant or very sitting sedentary lifestyle where we're in a chair or a desk all day can actually be harmful for our large intestine. So this exercise, movement, twisting, putting yourself upside down that you might not actually do in your regular life all the time is really really crucial. So microbiome is one of the components of our cells that is not actually our cells. So we talked about in the first lecture that we have trillions of cells, and then we have two or three times as many bacteria that are coating our digestive system and our skin. They have a really important role and so part of keeping our digestive system healthy is also keeping our microbiome healthy. They do really important things like, help us produce vitamins, help us break down foods that we might not be able to, help us absorb or create different types of nutrients. We probably have all had the experience of taking antibiotics, and maybe not feeling so well or having a doctor tell us to take probiotics at the same time. The reason for this is when you take antibiotics, you're actually sometimes killing off some of the good bacteria. Okay. So in addition to this main digestive track that we just went through, that's going to do the majority of mechanical and chemical digestion and it's going to be aided by movement, our entire digestive system is also going to be aided by accessory organs. The big three are; the liver, the pancreas and the gallbladder. Now, all three of these organs are going to help produce components that will aid in digestion, and absorption, and will be secreted into the digestive track at some point. First, I want to talk about the liver. The liver, I think it's a perfect name because you cannot live without it. It's one of the most important multifaceted organs that we're going to talk about. So some of the things that the liver can do, the liver actually has so many important functions. I'm just going to talk about a couple. So the liver filters our blood, right? Which is crucial. It stores byproducts of the red blood cells, but it's going to really filter out toxins from our environment. It's also going to store important things like glycogen, which is how we store sugar to make energy. Vitamins, it can make important proteins that we use in our immune systems, that we use in blood, and it's also going to help us break down fat and store cholesterol to be excreted. So these are all really really really important things. So the next one is pancreas. Now the pancreas has a whole variety of hormones and proteins that it's going to make that are directly going to affect things like the small intestine because it helps it to digest carbohydrates, digests proteins, digest fats. It's also going to be responsible for secreting certain hormones like, insulin and glucagon. The last secondary organ I'm just going to mention is the gallbladder. The gallbladder's main function is to store bile.
