Why is your poo loose when you have diarrhea?

Well, there are a lot of types and causes of diarrhea, and the cause of loose bowel movement depends on these causes. Primarily, the looseness is due to more rapid passage of your stool in the intestines. The large intestine is responsible for reabsorbing water from your stool. If you have diarrhea, due to increased peristaltic movement (i.e. intestinal contractions which moves food and undigested materials forward), there is decreased amount of time for your large intestines to dehydrate these food stuff. Furthermore, the mucus in the large intestines binds the stool. Again, if you have hypermotile bowels, there is less time to do this. Increased intestinal secretions, in secretory diarrhea, also contribute to the looseness.

Knickz explained it pretty well. The large intestine is responsible for absorbing the fluids from the digestive system. Your poo is basically like liquid until it reaches the large intestine, where the fluid is absorbed and it becomes more solid. Diarrhea is caused by you having a virus or bad bacteria in your digestive tract. Because there are germs in there, the body flushes it out, rather than absorbing these bad bacteria. This is why you should take extra effort to drink more fluids when you have diarrhea, because the lack of fluid absorption can quickly cause dehydration.

It is due to the fact it is broken down more by stomach acids, and your stomach acid is still in the stool, which is why it sometimes burns when you have diarrhea.

Why would you want to even know this?