About the Small Intestine

Your small intestine is a long tube that's about 1 1/2 inches to 2 inches around, and, if stretched out, is about 22 feet long. It is made up of three parts:

The Small Intestine

  • The duodenum, the C-shaped first part, which is attached to the stomach. After food combines with stomach acid and becomes chyme, it moves into the duodenum where it mixes with bile from the gall bladder and digestive juices from the pancreas.
  • The jejunum, which is the coiled midsection. Here food is further broken down into smaller bits of nutrients that continue to be absorbed into the bloodstream.
  • The ileum, the final section, which leads into the large intestine. This is the final and longest portion of your small intestine. Virtually all of the remaining nutrients are absorbed through the lining of the walls of the ileum.

The inner walls of your small intestine are covered with millions of microscopic, fingerlike projections called villi, which absorb nutrients into the body.

Essential to the function of the small intestine are the liver, gall bladder, and pancreas. The liver (located under the rib cage in the right upper part of your abdomen), the gallbladder (hidden just below your liver), and the pancreas (located beneath your stomach) are not part of the digestive tract, but are necessary for digestion.

The liver produces bile, which helps the body absorb fat. Bile is stored in the gallbladder until it is needed. The pancreas produces enzymes that help digest proteins, fats, and carbohydrates. These enzymes and bile travel through channels (known as ducts) directly into the duodenum, the first part of the small intestine.

Food may spend as long as 4 hours in your small intestine and will become a thin, watery mixture. What remains at the end of the ileum (last part of the small intestine) is mostly water, electrolytes (chemicals such as sodium and chloride), and waste products, such as fiber and dead cells shed from the lining of your digestive tract.

This leftover waste goes on to the large intestine.

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Last modified on: 30 June 2015

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