Back To CoursePathophysiology Textbook
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You'll most likely agree with me that when you're really sick, you just don't feel like eating. There's plenty of reason for it. Your body aches, you're all stuffed up, and you've got a massive fever. It's a perfect storm for inappetence.
And wouldn't you know it? When your gastrointestinal tract is sick, it doesn't eat either! Quite literally, it doesn't tear apart nor absorb nutrients that may be important for you.
In medicine, one of the most important things a doctor can do is get their patient absorbing nutrients from their digestive system as opposed to an IV drip. That's because it's so much better at providing for your body, nutritionally speaking.
That's why this lesson will focus on some of the things that can go wrong in the digestive system and how it is that they impact your absorption of life-giving nutrients.
I think it's fair to assume that when I talk about the digestive system, most people think of the stomach and intestines. Others may correctly point to the mouth, saliva, and esophagus as components as well. But I don't think too many people will jump to choose the pancreas, liver, and gallbladder right away.
These three are somewhat in the periphery of the digestive system since they're not directly part of the direct digestive chain of your mouth, esophagus, stomach, and intestines.
However, even though they're not part of this loop directly, they are important players in the absorption of nutrients. They're like special teams players that are on the sidelines but play critical roles at important points in a game.
Let's examine this further. The pancreas is most often associated with insulin production. This is true, without a doubt. And insulin is important in driving energy-giving sugar into your cells after a meal.
But the pancreas has a dual role. It's also something that produces enzymes, proteins that speed up biochemical reactions, which help you to digest your food. These enzymes help to digest fat primarily but also proteins and carbohydrates. If the pancreas malfunctions due to pancreatitis or the obstruction of the pancreatic duct, then these super-important enzymes won't make as much of an impact. This will lead to the malabsorption of nutrients out of your gut and into your body.
A disease affecting the pancreas isn't the only thing that can trigger poor absorption of your meals. Your liver produces a substance called bile. Bile is a greenish fluid produced by the liver and stored in the gallbladder, which aids in the digestion of fats.
If your liver is sick for any serious reason and this disease leads to its malfunction, then it can actually produce little to no bile or improper amounts of bile. This can cause the bile itself to solidify into gallstones. These gallstones can then lodge in the ducts that provide for the bile's outflow from the gallbladder and into the small intestines. This can conversely cause the gallbladder to get sick and infected, which only exacerbates the entire problem even more. Not to mention the fact that if the bile can't make it into the intestines, fat digestion and absorption will suffer.
I hope you can simply appreciate the convoluted nature of how diseases in the gastrointestinal system work. Everything affects everything else in some way. There's no such thing as a closed system in our examples.
Since the intestines are the guys responsible for actually absorbing our nutrients, and there's over 20 feet of them, I think it's important that we now focus in on them a little bit. They're like our main players on the football squad, always in the thick of the gritty action.
There are many processes that can cause malabsorption in the intestinal tract. If you've got a viral infection that causes you to have diarrhea, better known as the stomach flu, then you better believe you won't absorb as many nutrients or water as before. They're coming in one end and out the other in no time - faster than your favorite player can run a 100-yard dash! Due to that speed, your intestines will literally be unable to absorb the nutrients simply because the nutrients are moving too quickly.
Even more so, horrifically, if there are worms - yes, worms - in your intestines, then they may help themselves to a nice serving of some or most of your food (depending on how many there are) before you even get the chance to absorb it.
Oh, and let's not forget the ever-present bacteria. There are always bacteria in your gut. The problems begin only when either the wrong kind of bacteria gets into your body, resulting in things like diarrhea, or the number of bacteria increases beyond a reasonable amount. Small intestinal bacterial overgrowth is a state where the number of bacteria in the small intestine reach larger-than-normal levels. The large numbers prevent nutrients from being absorbed, or they destroy the lining of the intestines, which in turn leads to improper absorption of nutrients as well. If the cells that absorb your nutrients are fried due to a bacterial toxin, then they obviously can't help you get the most out of your food.
SIBO (small intestinal bacterial overgrowth) can be due to improper gastrointestinal motility, which doesn't empty out the small intestines very well, leading to over-accumulation of bacteria. It can also be due to improper secretion of substances that keep bacterial growth at appropriate levels. These substances include gastric acid, bile, and pancreatic enzymes. See? It told you everything was interconnected!
And if I haven't proven to you how all sorts of disease processes are connected, then consider celiac disease, a.k.a. celiac sprue. This disease has been linked to SIBO. Celiac disease is an autoimmune disease culminating in diarrhea, improper digestion and absorption as a result of gluten ingestion. More specifically, a gluten-derived protein, called gliadin, is what actually causes the problem. Gliadin causes immune system cells, called T-cells, to overreact and treat this particle as a foreign invader.
This causes serious inflammation in the upper portions of the small intestines because your body thinks it's using this inflammation for a good thing: to get rid of this supposed 'foreign invader.' But this inflammation negatively affects the intestinal villi, resulting in their loss or atrophy.
Intestinal villi are finger-like projections in the intestines responsible for nutrient absorption. If they atrophy - that is to say, decrease in size or are completely obliterated due to the inflammation - then the end result here is quite predictable: malabsorption in the GI tract, resulting in malnutrition.
But that's not all here. There are so many other causes of malabsorption. I know you know of at least one more famous one: lactose intolerance. In fact, lactose intolerance, a condition where an inadequate amount of lactase enzyme causes improper digestion of lactose, can be caused by something like celiac disease. Unless a person supplements their diet with lactase enzymes before they eat milk products, they may suffer from diarrhea.
What I wanted you to appreciate in this lesson weren't just all of the reasons why malabsorption in the GI tract can occur, not all of which did we cover, but also the utter inter-connectedness between the important parts we discussed. One wrong move in any part in the digestive system can set off an entire sequence of events that affects everything inside you.
We discussed how the pancreas produces enzymes, proteins that speed up biochemical reactions that help you digest your food and your liver produces a substance called bile. Bile is a greenish fluid produced by the liver and stored in the gallbladder, which aids in the digestion of fats. Both of these help you digest food and prevent bacterial overgrowth from occurring.
Bacteria aren't the only pathogens that cause malabsorption; we discussed how the stomach flu and worms also cause this.
Finally, we noted that autoimmune disease, such as celiac disease, a.k.a. celiac sprue, can cause malnutrition. Celiac disease is an autoimmune disease culminating in diarrhea, improper digestion and absorption as a result of gluten ingestion. Celiac disease can also predispose a person to lactose intolerance, which causes improper digestion of lactose.
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Back To CoursePathophysiology Textbook
20 chapters | 274 lessons