Gastrointestinal tract
The small intestine begins at the duodenum and is a tubular structure, usually between 6 and 7 m long. Its mucosal area in an adult human is about 30 m. Its main function is to absorb the products of digestion (including carbohydrates, proteins, lipids, and vitamins) into the bloodstream. There are three major divisions:
Large intestine
In mammals, the colon consists of five sections: the cecum plus the ascending colon, the transverse colon, the descending colon, the sigmoid colon, and the rectum.