Large intestine is the last part of the digestive system
Its function is to absorb water from the remaining indigestible food matter and then to pass useless waste material from the body. The large intestine, or colon, is connected to the small intestine at a T–shaped junction, where a sphincter (a muscular valve) controls the movement of material.
One arm of the T is a pouch called the cecum with a finger–like extension called appendix, which is dispensable. Lymphoid tissue in the appendix makes a minor contribution to body defense. The main branch of the human colon is about 1.5 m long.
A major function of the colon is to recover water that has entered the alimentary canal as the solvent of the various digestive juices. About 7 liters of fluid are secreted into the lumen of the digestive tract each day, which is much more liquid than most people drink. Most of this water is reabsorbed when nutrients are absorbed in the small intestine. The colon reclaims much of the remaining water that was not absorbed in the small intestine. The small intestine and colon together reabsorb about 90% of the water that enters the alimentary canal. The wastes of the digestive tract, the feces, become more solid as they are moved along the colon by peristalsis. The terminal portion of the colon is called the rectum, where feces are stored until they can be eliminated.