What happens in the small intestines of the digestive system?

Answer 1

First, the contents in the stomach slowly moves into the small intestines-- the contents does not "dump" all at once. The material by then has been masticated (chewed) in your mouth, with saliva adding to the break down, and in the stomach exposed to acids and bile salts that broke down the food into a chunky mush.

Second, as the chunky mush enters the small intestines, it is exposed to several forces. One is that the small intestines pulls in fluid from cells to make the MASH more "soupy". Another force is muscular as the mush is moved through about 20 feet (6 meters) of coiled up small intestines. It is not a straight tube, but has many bends and a large surface area that allows the body to start immediately receive nutrients. Cells get numerous micro-nutrients as the mush moves along. By the time the small intestines are done with their job, it has pulled out every bit of good parts of the food you eat. But it cannot send that soupy mix on, or humans would have constant diarrhea. So first, the body must begin pulling out the liquidy part. That gets shuttled to the kidneys for processing, while also keeping your body hydrated.

Third, the mixture now begins to move into the large intestines, about FIVE feet (1.5 meters) of loops. The difference in length is because the small intestines must do so much more work. The large intestines is mostly responsible for compacting the mixture and preparing it into a "bowel movement". The shape of a formed bowel movement is primarily just the shape of the tube.

Now, if there was a problem in the small intestine, such as if you have a bacterial or viral stomach infection, then the small intestines cannot pull off as much fluid. So you might feel intestinal cramps and feel ill, and experience diarrhea, because the large intestines are not responsible to send fluid to the kidneys like what goes on in the small intestines.