Stomach. In the stomach, acids and stomach motion break food down into particles small enough so that nutrients can be absorbed by the small intestine.

Small Intestine. The small intestine, despite its name, is the longest part of the gastrointestinal tract and is about 20 feet long. Food that passes from the stomach into the small intestine first passes through three parts:

• First it enters the duodenum
• Then the jejunum, and
• Finally the ileum

Most of the digestive process occurs in the small intestine.

Large Intestine. Undigested material, such as plant fiber, is passed to the large intestine, mostly in liquid form. The large intestine is approximately 6 feet long and is the final portion of the digestive tract. It follows the small intestine and includes the cecum, the appendix, the colon, and the rectum, which extends to the anus.

Cecum and Appendix. The cecum and the appendix are located in the lower-right quadrant of the abdomen.

Colon. The colon absorbs excess water and salts into the blood. The remaining waste matter is converted to feces through bacterial action. The colon is divided into four major sections:

• The first section, the ascending colon, extends upward from the cecum on the right side of the abdomen.
• The second section, the transverse colon, crosses the upper abdomen to the left side.
• The third section extends downward on the left side of the abdomen toward the pelvis and is called the descending colon.
• The final section is the sigmoid colon.

Rectum and Anus. Feces are stored in the descending and sigmoid colon until they pass through the rectum and anus. The rectum extends through the pelvis from the end of the sigmoid colon to the anus.

Click the icon to see an image of the digestive system.

Click the icon to see an image of the stomach.

Click the icon to see an image of the small intestine.

Click the icon to see an image of the large intestine.

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Review Date: 09/28/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)