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Absorption of Nutrients_Final

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>> Hi there. Are you familiar with the old adage, "You are what you eat?" There is some truth to this, but it's probably more accurate to say, "You are what you absorb." We've covered a lot so far in the process of digestion and how food is broken down into digestible pieces. But perhaps, the most important phase of digestion is if and how those nutrients are absorbed. If this step doesn't happen, then all of that energy digesting was for nothing. Here's the thing. You could be absorbing anywhere from 10-90% of your nutrients and that is a really big discrepancy. Some cases of obesity are even a result of poor absorption, because if you're not absorbing your food properly, your body will want to eat more in order to feed your starving cells, even when you've had more than enough calories. This is where the calories listed on a package can lead you and your clients astray. Also, remember that calories are always an estimate. No one actually goes in and chemically measures exactly how many carbs are in your slice of bread. When you look at a calorie count, it's just an estimate of an average piece of bread that's roughly the same size pulled from a database. When it comes to supplementation, herbs, or medicines, remember, these have to be absorbed through the digestive system too, so absorption is really the root of health or disease. Now that you know that the digestive tract is a tube that exists outside of your body, you can understand that just because you put something in your mouth doesn't necessarily mean you'll be able to make use of it in your body. Let's look at what this means by taking a closer look at absorption. Absorption is regulated by the secretion of enzymes, mucus, and other fluids, and motility, the rate at which the digestive process takes place. Digested foods that have been through the process should be able to pass through the blood vessels behind the intestinal walls, either by diffusion or active transport. Diffusion is when nutrients pass through the mucosal wall of the small intestine. Active transport is when one molecule attaches to another in order to be transported through the circulatory or lymphatic system. There are two ways that nutrients are taken into the body to newer cells, through the bloodstream, and the lymphatic system. When the cells receive nutrients in a usable form, they can metabolize them. Metabolism is the sum of all the chemical reactions in the body from digestion to the use and storage of energy in individual cells. In this course, we'll focus only on digestion. Digestion is a process of absorption and secretion of fluids and nutrients. Throughout the entire process, the tube inside your digestive tract, known formally as the lumen, takes in nine liters of liquid and a total of nine liters has to be removed. When this balance is out of whack, you can end up with things like dehydration, since seven liters of this fluid come from within your body. This is one-sixth of your total body fluid. This liquid comes in the form of saliva, bile, water, electrolytes, mucus, and enzymes. For the overall breakdown, refer to the Absorption Input and Output handout in your Learning Center. For now, know that your body fills the lumen with all that it needs to break down food and then absorbs the nutrients and fluids back into the system leaving only waste behind. Nutrients must cross the intestinal wall and a layer of interstitial fluid via capillaries or lymph vessels to reach the blood or lymph system. The majority of nutrients and fluid absorption takes place in the small intestine, which is divided into three parts, the duodenum, the jejunum, and the ileum. The duodenum is the first section of the small intestine. This is where the pancreas and the liver secrete enzymes when chyme is present. The jejunum, the middle section of the small intestine takes on the bulk of the absorption responsibility. We'll talk about how it does this when we look at the intestinal wall. Lastly, the ileum, the last part of the small intestine, functions mainly to absorb vitamin B12 and bile salts. The cells on the wall of the ileum also secrete more enzymes to keep the digestive juices flowing. Some of these enzymes stay on the wall and are reused every time. Lactase is an example of an enzyme that lives on the wall of the intestines, for the few of us that are lucky enough to have it, although most of us don't. Almost 7 to 8 liters of fluid are absorbed in the small intestine, leaving only about 1.5 liters to pass along into the large intestine. That's a lot of absorption. It's why the small intestine has so many folds and flaps for the purpose of more nutrients absorption. The intestine increases its surface area for absorption even more through villi, which are little wave-like hairs along the wall of the intestine, and every villi has hairs called microvilli. Altogether, this provides enough surface area to fill out an entire tennis court. You can tell our bodies don't want to miss a thing. Each villi or hair-like structure on the intestinal wall contains capillaries and lymphatic tubes to absorb nutrients and carry them through the intestinal wall. Let's take a closer look at the intestinal wall, which is the surface area that brings in all of these nutrients. There are four layers of mucosal lining along the alimentary canal or digestive tract. These are the same four layers of tissue that lined all the cavities or lumen in our bodies. Lumen just means inside of a tube. The four layers of mucosal lining are the mucosa, the sub mucosa, the muscularis, and the serosa. We said before that the gut is lined with a layer of epithelial cells just like all parts of the body that come in contact with the outside world. Epithelial cells have two functions, to absorb nutrients and to keep out harmful substances. The epithelial layer is lined with tight junctions, which we'll talk about later on when we discuss leaky gut. Tight junctions must be, well, tight in some areas to keep potential irritants where allergens from passing through. And they need to be loose in other areas to let the nutrients through. The mucosal layer is the first layer surrounding the lumen. This layer is regenerative. These cells renew every three to four days. They have to deal with so many toxins that these cells have a really short life. This layer also secretes mucus to prevent the acid and enzymes from digesting themselves. The second layer, the sub mucosa is below the mucosa layer. This layer has folds with larger blood vessels and lymphatic vessels which provide a means of absorption. This layer also contains the submucosal plexus, one of the two major nerve networks in the enteric nervous center or the nervous system that controls the gut. That's right, the gut has its own nervous system, but we're gonna go into that a little bit later. The third layer is the smooth muscle called the muscularis. Smooth muscle means it's not under conscious control. This is the muscle responsible for the peristalsis motion that happens in the esophagus and the small intestine. It contracts in a way that decreases the diameter of the lumen as well as the length to shorten the tube. These two actions keep things moving along. The second nerve network of the enteric nervous system, the myenteric plexus lies between the muscles in this layer. We'll speak about the nerves in the nervous system in the gut later. For now, just know that these nerves are in the gut lining. You can also refer to the gut wall diagram for more information. The serosa or the last layer is connective tissue that attaches the organ to the abdominal wall. The serosa adds a little stability so that your organs don't float around while still providing mobility. Sounds like the perfect formula for life. Most nutrients travel through the capillaries to the bloodstream, but fat cannot be directly absorbed into the blood or else it would clog our arteries. Instead, fat is transported via the lymphatic system. A couple of notes about the lymphatic system. Unlike blood, it's not attached to a pump, so to move about it mostly relies on gravity. Our muscles in the legs, for example, pump the fluid in the lymph back up, but we're still fighting gravity. Ever had swollen ankles after a long day? That's the fluid pooling. And this is the same reason we often wake up with puffy eyes. We didn't have gravity working for us all night to drain the fluid. Nurses who are on their feet all day often wear a compression socks to keep that lymph fluid up by constriction. Unlike blood vessels, the lymphatic system isn't filtered through the liver. Any nutrients that enter go straight into our bodies without the final stage of filtering that the liver provides. This may be something to consider when consuming fats. It's a good reason to make sure that they are of the highest quality. In addition to being a channel for fat, the lymphatic system also provides transportation for vitamins that are not water soluble. These vitamins attach to a fat and travel through the lymph. Also, when the body is unable to fully break down a protein, it can enter the lymphatic system as well. Since this molecule is unfamiliar, the immune system may attack it, causing an allergy. This is one reason why some people are allergic to certain proteins like peanuts. When it comes to the absorption of vitamins, some of them need a carrier. Vitamin B12, for example, must be coupled with intrinsic factor or a protein in order to be broken down in the stomach and absorbed in the ileum of the small intestine. Now let's talk about how inflammation can play a role in absorption. Behind the layers of the intestinal wall is interstitial fluid. When there's inflammation in the gut, there is essentially more liquid between your mucus wall and the capillaries. This makes it harder for nutrients to get across the mucosal wall. So someone may be eating all the right food, they may even be digesting the right nutrients, but they're having absorption problems because the nutrients are having trouble making it through the extra fluid. These are all important things to consider because if your clients can't absorb their nutrients, they won't be receiving the building blocks they need to function optimally and then it doesn't really matter how many veggies they eat. We'll go over the signs of malabsorption later in this course. So to recap, the main function of digestion is to break particles down small enough so that they can be absorbed in the blood or the lymphatic system and travel to where they are needed most. Proteins and carbs are absorbed via capillaries to the blood vessels and fats are absorbed through the lymphatic system. The intestinal walls are structured in little folds and with little hairs to have the most surface area possible for maximum absorption. All of this is in place to help us get the most out of our food. Now that you know how hard your body is working, pumping fluids in and out, does that change your desire for what you want to put in? Share your thoughts on the Facebook group. Until next time, when you're ready to absorb even more.

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Duration: 10 minutes and 54 seconds
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Language: English
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Posted by: ninaz on Mar 21, 2018

Absorption of Nutrients_Final

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