The gastrointestinal (GI) tract

Digestion, or transit time, is the time it takes the food to go from the mouth to the exit (be it the anus or the stoma). Transit time varies from person to person. On average, it takes 6-8 hours for the food to go from your mouth, through your stomach, and through the small intestine.  Following the small intestine, food enters the colon, or large intestine, for absorption of water and elimination of what is left, which can take about 40 hours. Several studies have shown that average time from entrance (mouth) to exit (anus) is about 53 hours.

For people with an ostomy, the amount of bowel removed during surgery and the location of the stoma in the digestive system will cause transit time to change.

The normal digestive tract and how it works

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Food enters the digestive tract through the mouth. After it is chewed and swallowed, it moves down the esophagus to the stomach.  From there it goes to the small intestine. Almost all the digestion and absorption of nutrients takes place in the small bowel (another name for intestine).

After about 6-8 hours, what is left of the food moves into the large intestine (also called the colon).  The movement of the bowel that pushes the food along is called peristalsis.  You cannot feel this movement.  If you have a stoma, which is a piece of bowel brought out to your abdomen, you can see the stoma move.  Peristalsis happens all the way through the digestive tract (also called the GI tract or gastrointestinal tract).

From the large intestine, the residue of the food moves into a storage area called the rectum.  Water is absorbed from the food reside in the colon, making the food residue firm. The stool or food residue is ready to pass out through the anus.

Small intestine (made up of 3 sections)

  1. duodenum: about 10-12 inches long starting at the end of the stomach
  2. jejunum: about 8-9 feet long
  3. ileum: about 12 feet long. It connects to the large bowel

Large intestine

  • also called large bowel or colon
  • is 5-6 feet long
  • There are five parts:
  1. Cecum: the area where the small and large intestines join. There is a one way valve that keeps food from going back into the small intestine. The contents of the bowel in this area are quite liquid.
  2. Ascending colon: the contents here are still fairly liquid. This section goes up the right side of the abdomen.
  3. Transverse colon: the contents of the bowel are now less liquid. This section goes across the abdomen.
  4. Descending colon: the contents of the bowel in this section are more formed. This part of the bowel goes down the left side of the abdomen.
  5. Sigmoid colon: the contents of this part of the bowel are usually solid. The sigmoid colon is S-shaped, curving from the end of the descending colon to the rectum.

The Rectum and Anus

The rectum is the last part of the large intestine and its contents are usually solid.  Nerves going to the brain signal us when stool moves into the rectum. These signals tell us it is time to have a bowel movement.

The anus, or anal sphincter, is a muscle valve that allows us to control when to have a bowel movement.  This is the only part of the digestive tract that we have control of.