The intestine is the portion of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine. In humans, the small intestine is further subivided into the duodenum, jejunum and ileum while the large intestine is subdivided into the cecum, colon and rectum.
The intestine is the part of the body responsible for extracting nutrition from food. While the stomach's role mainly consists in "breaking" food molecules into nutrients, the intestine allows these nutrients to enter the blood via its dedicated membrane.
The small intestine has a particular folded texture in order to increase the surface area available for diffusion of nutrients through the intestinal wall so they can be absorbed. These microscopic folds are called microvilli. In an adult human, the small intestine is, on average, about seven meters long.
The large intestine hosts several kinds of bacteria that deal with molecules the human body is not able to destroy itself. This is an example of symbiosis. These bacteria also account for the production of methane inside our intestine (which is released as flatulence when removed through the anus).
Diseases of the intestine
Gastroenteritis is inflammation of the intestines and is the most common disease of the intestines. It can arise as the result of food poisoning.
Ileus is a blockage of the intestines.
Appendicitis is inflammation of the vermiform appendix located at the cecum. This is a potentially fatal disease if left untreated; most cases of appendicitis will require surgical intervention.
Crohn's disease and ulcerative colitis are examples of autoimmune diseases affecting the intestines.