What Is the Digestive System?

The digestive system is how your body gets nourishment

The human digestive system as seen from the front.
The digestive system begins at the mouth and ends at the anus. Encyclopaedia Britannica/UIG/Getty Images

The digestive system is the group of organs that break down food in order to absorb nutrients. The nutrients in food are used by the body as fuel to keep all the body systems working. The leftover parts of food which cannot be broken down, digested, or absorbed are excreted as bowel movements.

There are several organs in the digestive system, all with a role in breaking down food and managing waste material.

The digestive tract forms one long tube through the body, all the way from the mouth to the anus (with some sphincters between organs to keep things moving the right way). The organs in the digestive system, in the order in which food travels through them, are:

  • Mouth: Digestion starts at the very beginning, with food being chewed in the mouth. Food is broken down into smaller pieces and the saliva in the mouth begins digesting it.
  • Esophagus: The esophagus is a tube that's inside the throat. After food is chewed and swallowed, it travels down through the esophagus and to the stomach.
  • Stomach: After the food is deposited in the stomach, the digestive process continues. The food is mixed with the acids and enzymes that are secreted from the stomach wall. After the food is thoroughly broken down, it is moved along into the small intestine.  
  • Small Intestine: The small intestine is a long tube where most of the vitamins and nutrients are absorbed from food. More enzymes are added into the small intestine as the food moves through to help facilitate the process.
  • Large Intestine: After moving through the small intestine, what is now partially digested and mostly liquid food enters the large intestine. The large intestine is where much of the water is absorbed from the waste material. By the time the stool reaches the end of the large intestine it is in a more solid form.
  • Rectum: At the end of the large intestine is the rectum, a reservoir that holds stool until it can be passed out of the body. When the rectum becomes full with stool, it gives off a signal that it's time to go to the bathroom.
  • Anus: The anus has two sphincters that serve to hold stool inside the body until it is time to pass it. When a person consciously relaxes their external sphincter, the stool can then leave the body. 

Crohn's disease, one form of inflammatory bowel disease (IBD) can affect any of the organs in the digestive tract, though the small intestine and large intestine are the ones that are most often involved. Ulcerative colitis, a second main form of IBD, primarily affects the large intestine. Both forms of IBD can also involve parts of the body outside the digestive tract.

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