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
The colon is the largest portion of the large intestine, so many mentions of the large intestine and colon overlap in meaning whenever anatomic precision is not the focus. Most sources define the large intestine as the combination of the cecum, colon, rectum, and anal canal. Some other sources exclude the anal canal.