Intestine is the muscular tube in the body through which food and the products of digestion pass. It extends from the lower end of the stomach to the anus, the lower opening of the digestive tract. It is divided into two sections called the small intestine and the large intestine. The intestine is also called the bowel.
The small intestine
is a narrower tube than the large intestine. It is about 22 feet (7 meters) long and empties into the large intestine. The small intestine carries on most of the digestive process. Digestive juices, or enzymes, secreted or manufactured by the walls of the small intestine, together with enzymes from the liver and pancreas, complete the digestion of foods.
The small intestine also is the main organ of absorption in the body. Digested food passes through tiny fingerlike projections in the wall of the small intestine. These projections, called villi, are lined with a single layer of cells and increase the absorbing surface of the walls of the small intestine. As food passes through the villi, some of it goes into tiny blood vessels in the villi and the rest passes into lacteals (lymph vessels). Digested food that passes into the lacteals is called chyle. Chyle travels through the thoracic duct to the neck where it is released into the blood.
The large intestine
is about 5 feet (1.5 meters) long and is made up of the cecum; the ascending, transverse, descending, and sigmoid portions of the colon; and the rectum. The large intestine absorbs water and salts from the material that has not been digested as food, and eliminates wastes from the body.
