It's been a long time since I have been able to get to another post, and for that I apologize. I was able to have a nice family vacation at the end of February, and then, well, my brain was shut off for a while. Still not sure if it is on yet, but here goes.
Our last couple of posts dealt with the lungs and the heart, but now I think it's time to move on. Time to get down and dirty with the food pipe. The G.I. tract. The sh#t factory. Exciting? Maybe not. Essential? Most definitely.
I thought today we would just talk a little bit about the anatomy of the GI tract first, and then in subsequent posts move on to more specific parts of the system. Ready? Here we go....
Triple Venti Half Sweet Non-Fat Caramel Macchiato
In the most simplest form, the Gastrointestinal (GI) tract can be thought of as a coffee maker. Yes, a coffee maker. Think about it. What do you need to make coffee? Well, you need to start with a food substance, grind this up, add some stuff to it, mix it together, and then filter the stuff that you want away from the stuff that you can throw away. Coffee beans ground up and mixed with hot water can be filtered into coffee (mmmm...) and coffee grounds. Simple.
The GI tract is like this too, and in general terms performs all of these functions. Let's start with the coffee grinder.
The Upper GI Tract - A Bit of a Grind
Our last couple of posts dealt with the lungs and the heart, but now I think it's time to move on. Time to get down and dirty with the food pipe. The G.I. tract. The sh#t factory. Exciting? Maybe not. Essential? Most definitely.
I thought today we would just talk a little bit about the anatomy of the GI tract first, and then in subsequent posts move on to more specific parts of the system. Ready? Here we go....
Triple Venti Half Sweet Non-Fat Caramel Macchiato
In the most simplest form, the Gastrointestinal (GI) tract can be thought of as a coffee maker. Yes, a coffee maker. Think about it. What do you need to make coffee? Well, you need to start with a food substance, grind this up, add some stuff to it, mix it together, and then filter the stuff that you want away from the stuff that you can throw away. Coffee beans ground up and mixed with hot water can be filtered into coffee (mmmm...) and coffee grounds. Simple.
The GI tract is like this too, and in general terms performs all of these functions. Let's start with the coffee grinder.
The Upper GI Tract - A Bit of a Grind
The upper tract are the elements of the GI tract that we may be most familiar with. And, if you have been reading this blog from the beginning, we are actually talking about the tube AND the circle. Gums, teeth, tongue, pharynx, larynx, esophagus, stomach, and the duodenum all make up this first part, or "upper gastrointestinal tract". Now, we all know that the teeth perform a significant part of the "grinding" portion of our food, but the stomach also plays a big role in getting those tacos ready for further digestion in the more distant bowels of the bowels. The stomach is basically a big muscle bag, and it churns and grinds the food into a sludge that is more easily passed through the system. This step is really important for digestion, which we will get to later.
No Additives? Fuggedaboutit
We also need to add water to make coffee, and thus our body needs to add stuff to the food to make our "coffee". We certainly can add water by drinking it, but the more important things added in the upper tract are saliva and stomach acid. These help to begin digestion from the mouth on down. Saliva? Yes, not just for sidewalks, it contains many things, but important to digestion of food is amylase (for breakdown of starch and sugars) and lipase (for breakdown of fats). Saliva is also mostly water and mucous and anti-microbial compounds too. Think about that the next time someone gleeks on your face. Stomach acid (or gastric acid) is mostly made up of hydrochloric acid and other digestive substances that begin the process of protein digestion, as well as continuing the breakdown of sugars and fats. The churning action of the stomach muscle, the saliva, the stomach acid, and the chewed up fish tacos all form a slurry of nutrient goodness that is then passed out of the stomach and into the duodenum (first portion of the small intestines). Anything else? Of course! We needs to gets us some bile and pancreatic juices, yo! Bile comes from the gallbladder (basically a storage facility for the liver - more on that later in another post), and pancreatic juice from the (you guessed it) pancreas. These substances contain a whole host of digestive goodies that continue to aid in the digestion and breakdown of our food products. The stuff that is passing through now, think of this as what you would see inside the coffee maker as the grinds are mixing with the hot water. Not quite ready for prime time, but dang, looking good....
The Lower GI Tract - Absorby McFilterson
Where do we begin? Well, technically the lower GI tract begins before the duodenum even ends (WTF?). Yes, the first 2/3 of the duodenum is considered part of the upper tract, and a transition point (at the ligament of Treitz) thus begins the lower GI tract. The lower tract is made up of the rest of the small intestines (some of that duodenum, the jejunum, and the ileum) and then the large intestines, also referred to as the colon.
No Additives? Fuggedaboutit
We also need to add water to make coffee, and thus our body needs to add stuff to the food to make our "coffee". We certainly can add water by drinking it, but the more important things added in the upper tract are saliva and stomach acid. These help to begin digestion from the mouth on down. Saliva? Yes, not just for sidewalks, it contains many things, but important to digestion of food is amylase (for breakdown of starch and sugars) and lipase (for breakdown of fats). Saliva is also mostly water and mucous and anti-microbial compounds too. Think about that the next time someone gleeks on your face. Stomach acid (or gastric acid) is mostly made up of hydrochloric acid and other digestive substances that begin the process of protein digestion, as well as continuing the breakdown of sugars and fats. The churning action of the stomach muscle, the saliva, the stomach acid, and the chewed up fish tacos all form a slurry of nutrient goodness that is then passed out of the stomach and into the duodenum (first portion of the small intestines). Anything else? Of course! We needs to gets us some bile and pancreatic juices, yo! Bile comes from the gallbladder (basically a storage facility for the liver - more on that later in another post), and pancreatic juice from the (you guessed it) pancreas. These substances contain a whole host of digestive goodies that continue to aid in the digestion and breakdown of our food products. The stuff that is passing through now, think of this as what you would see inside the coffee maker as the grinds are mixing with the hot water. Not quite ready for prime time, but dang, looking good....
The Lower GI Tract - Absorby McFilterson
Where do we begin? Well, technically the lower GI tract begins before the duodenum even ends (WTF?). Yes, the first 2/3 of the duodenum is considered part of the upper tract, and a transition point (at the ligament of Treitz) thus begins the lower GI tract. The lower tract is made up of the rest of the small intestines (some of that duodenum, the jejunum, and the ileum) and then the large intestines, also referred to as the colon.
There is continued digestion in these parts, as all of the stuff entering in from the stomach and duodenum continues to mix and grind like the dance floor at a college campus bar. However, and more importantly, this is where the absorption of nutrients really starts to ramp up. Sugars, fats, and protein
(oh my!) are all being sucked out of the intestines and into the very complex network of blood vessels that surrounds these food pipes. Different parts of the small intestine are uniquely structured to maximize absorption of certain nutrients, all while keeping unwanted substances (i.e. coffee grounds) out.
Breakdown, absorb, filter, and excrete. This is all happening in the small intestines as you read this. But what about absorption in the large intestines? Will it ever stop? Yo, I don't know....well, actually we do know. Large intestines also absorb nutrients, but their major function is actually the reabsorption of water back into the blood stream. And we all know how important this job is, and the delicate balance of too little water reuptake (diarrhea) versus too much (sh#ttin' bricks).
The intestines absorb what we need, and keep out what we don't. The stuff we don't need is collected in the rectum until such time that it becomes full enough to signal our brain to release "the one in the chamber". Intestines also help to dispose of certain wastes from the body, like bilirubin, which is the breakdown product of red blood cells that is excreted in bile and is what makes our stools that oh-so-familiar brown colour.
Do they always function perfectly? Of course not. Bowel dysfunction is a major cause of disability the world over. Can they be afflicted with disease? Dang straight, some of which make daily living complex, painful, and (occasionally) bloody. Are we going to get to all of these discussions today? No way no how. However, the other supplementary organs of the digestive tract, like the liver and pancreas, are all overwhelmingly interesting topics to themselves. We will get to those later, as well as diseases and conditions of the GI tract in subsequent posts. Let's get down with brown!
(oh my!) are all being sucked out of the intestines and into the very complex network of blood vessels that surrounds these food pipes. Different parts of the small intestine are uniquely structured to maximize absorption of certain nutrients, all while keeping unwanted substances (i.e. coffee grounds) out.
Breakdown, absorb, filter, and excrete. This is all happening in the small intestines as you read this. But what about absorption in the large intestines? Will it ever stop? Yo, I don't know....well, actually we do know. Large intestines also absorb nutrients, but their major function is actually the reabsorption of water back into the blood stream. And we all know how important this job is, and the delicate balance of too little water reuptake (diarrhea) versus too much (sh#ttin' bricks).
The intestines absorb what we need, and keep out what we don't. The stuff we don't need is collected in the rectum until such time that it becomes full enough to signal our brain to release "the one in the chamber". Intestines also help to dispose of certain wastes from the body, like bilirubin, which is the breakdown product of red blood cells that is excreted in bile and is what makes our stools that oh-so-familiar brown colour.
Do they always function perfectly? Of course not. Bowel dysfunction is a major cause of disability the world over. Can they be afflicted with disease? Dang straight, some of which make daily living complex, painful, and (occasionally) bloody. Are we going to get to all of these discussions today? No way no how. However, the other supplementary organs of the digestive tract, like the liver and pancreas, are all overwhelmingly interesting topics to themselves. We will get to those later, as well as diseases and conditions of the GI tract in subsequent posts. Let's get down with brown!