The intestines are a long, continuous tube running from the stomach to the
anus. Most absorption of nutrients and water happen in the intestines. The
intestines include the small intestine, large intestine, and rectum.
The small intestine (small bowel) is about 20 feet long and about an inch in
diameter. Its job is to absorb most of the nutrients from what we eat and
drink. Velvety tissue lines the small intestine, which is divided into the
duodenum, jejunum, and ileum.
The large intestine (colon or large bowel) is about 5 feet long and about 3
inches in diameter. The colon absorbs water from wastes, creating stool. As
stool enters the rectum, nerves there create the urge to defecate.