The small intestine consists of the duodenum, jejunum and ileum. The small intestine is subdivided into the duodenum, the jejunum and the ileum. Carcinoid tumors of the midgut (jejunum, ileum, appendix, and cecum) are associated with carcinoid syndrome. The jejunum and ileum receive blood from the superior mesenteric artery. The villi in the jejunum are much longer than in the duodenum or ileum. Vitamin B is absorbed in the jejunum and ileum by passive diffusion. The digestive tract continues as the jejunum which continues as the ileum. It has three parts, the duodenum, jejunum and ileum. The division between the jejunum and ileum is not anatomically distinct. It then proceeds to the small intestine (duodenum and ileum) where most digestion occurs. In humans, the sites of tissue injury include the jejunum, the ileum, and the colon. There is no line of demarcation between the jejunum and the ileum. The jejunum seems to blend with an exceptionally short ileum. Supplies the cecum, ileum, and appendix. It is a common symptom of gastrojejunocolic fistula and intestinal obstruction in the ileum.