How Does the GI Tract Work?

The human body is a comprised of a number of complex systems. One of those systems is the gastrointestinal tract, which is composed of a line of different hollow organs located between the esophagus and anus. The gastrointestinal tract is essential for supplying nutrients to the body and eliminating waste products. All the organs work together to achieve this result, but each part serves a different function.

Parts

• The gastrointestinal tract is composed of three major parts. Each section performs a different function. The three major parts are the stomach, the small intestine and the large intestine. The small intestine is subdivided into three separate, but closely related, parts: the duodenum, the jejunum and the ileum. The large intestine is comprised of the colon, the rectum and anal canal. Muscle contractions in each organ push material from one section to the next.

Stomach

• Food and liquids are moved into the stomach by the esophagus, which connects the throat to the stomach. A sphincter at the connection of the esophagus and stomach generally prevents movement back up the esophagus. The stomach's first purpose is to store food and drink. Next, the lower part of the stomach breaks the contents down by mixing them with acid. Different types of food require different amounts of time to break down. Once this is finished, the stomach moves the material into the small intestine.

Small Intestine

• The three parts of the small intestine are essentially the same in make up and function. The food is mixed with acids and bile from both the small intestine and two other organs, the pancreas and the liver. The pancreas contributes a fluid that breaks down carbohydrates, fats and protein. The liver produces bile, which primarily breaks down fat. Enzymes contained in the acids digest the nutrients of the food and absorb them through the intestine walls for use in the body. Undigested waste is pushed into the colon.

Large Intestine

• The large intestine is the end point of the gastrointestinal tract. The undigested material from the small intestine consists mainly of indigestible fiber. It enters first into the colon, which absorbs water, electrolytes and vitamins from this material. The colon then stores this fecal material until it is to be expelled. Once a sufficient amount has been accumulated, the waste moves into the rectum. From there, the waste is expelled via muscle contraction through the anal canal.