The small intestine starts at the duodenojejunal flexure and ends at the caecum. The average length of the digestive tract is 450 cm. 260 cm of it belongs to the small intestine. The proximal 2/5 of the small intestine is called the jejunum, and the distal 3/5 is the ileum. The diameter of the small intestine is approximately 2.5 – 3.5 cm. The large intestine starts at the ileocecal valve and ends at the anus. On average, it is 150 cm long. The largest diameter is at the level of the cecum.