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:
Small intestine (Chinese medicine)
Transporting point of SI: Urinary Bladder 27. Conception vessel – anterior midline from perineum to lower lip. This is also the Alarm point for the SI which is called "Gateway to the Source"(guan yuan). Governing vessel is from perineum, to spine to crown of head down to upper lip.