As far as I can see, this question hasn’t be asked here. It puzzles me, and I suspect it might puzzle others.
The digestive tract (stomach and intestines) is full of things like bacteria and acids that are there to rapidly digest any food (including meat) that comes its way. This is true of humans, but also of all the other vertebrates.
So, what stops these things from digesting the body that surrounds them? In other words, why doesn’t the digestive tract digest itself, and then go on to digest the rest of the body? What is there in the stomach walls and the intestines that stops this happening?
For 1 thing an animal could not survive and reproduce if their digestive tract can get screwed up by stomach acids. There is a lining that protects against the acid.
The two biggest factors are the fact that you’ve got gastric mucosal tissue lining the stomach- basically producing a layer of mucus about 1mm thick to keep the stomach acid tissue away from the actual lining of the stomach. Also, the stomach tissue ishighly glandular and specialized to adapt to this situation. The image basically shows TONS of glandular tissue (the pink and purple bubbly looking stuff) before you get down to the actual inner (or outer depending on which way you want to think about it) muscular layer of the stomach. You also have a pyloric sphincter which keeps the stomach acid contained within the stomach, and basically opens up to the duodenum only when food is going to pass on to the next stage- this is basically why the stomach acids tend to stay only in the stomach area- you also have the Bile enzymes and such from the gallbladder all connected to that same area- so as soon as the food AND acid pass from the pyloric sphincter to the duodenum, the biliary enzymes (Which are MUCH more basic) will help to neutralize the acids (as well as emulsify fats- this is where fats get digested- in the duodenum, not the stomach).
Those are the two biggest factors: the inner layer of mucus that is continuously being produced by the stomach to protect itself (as well as the fact that the cells that line the stomach also tend to continuously regenerate as well, so there’s a high turnover constantly going on), and the fact that you’ve got sphincters at both ends of the stomach to keep the acid all in one place as well.
When things go wrong- like the mucus wears down and all in a certain area- that’s when you can have things like Ulcers in the stomach which can be problematic. Also, GERD: Gastro-esophageal reflux is another issue that can happen when the esophageal sphincter to the stomach opens up and the acid goes up and into the esophagus. Same with heart burn- that burning sensation. Others can have a similar painful sensation after eating a really fatty meal- this is more in the pyloric sphincter, when it’s continuously being used, or it’s started to not hold as well as it used to, and the acids go out an irritate the tissue.
Also, the body tries to maintain homeostasis by a variety of chemical interactions with hormones and peptides and such that basically regulate WHEN your stomach increases it’s stomach acids and when it decreases production of stomach acid- so it’s not like your stomach is always on trying to eat away at itself. The body tries to keep it down, until it senses the regulatory peptides that will increase the production of acid, digestive enzymes, and churning of the stomach. For more info, here’s the wikion it.
A doctor I’m not, but my son was hospitalized last year with multiple internal injuries as a result of an auto accident. So, out of necessity I learned somethings about somethings. One was about the enzyme Lipase, which is produced by the Pancreas. It finds its way into the Duodenum to facilitate digestion. My sons Pancreas was producing too much of it. At normal levels it does just what it’s supposed to do. However, at elevated levels, and because it’s so “strong,”, it can, in essence, start digesting anything it touches.
I guess you could say that that this is an example of a body digesting itself.
