The duodenum is the first part of the small intestine. It is located between the stomach and the middle part of the small intestine, or jejunum.
The absorption of vitamins, minerals, and other nutrients begins in the duodenum.
McKenzie S, Evers BM. Small intestine. In: Townsend CM Jr, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 19th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 50.