Small intestine anatomy diagram – The primary purpose of the small intestine is the absorption of nutrients and minerals from food intake. The small intestine is part of the digestive system. It is a hollow, tube organ that connects to the stomach and the large intestine. Small intestine is a long, narrow, folded or coiled tube; it is the region where most digestion of food occurs. The small intestine is made up of the duodenum, jejunum, and ileum. Together with the esophagus, large intestine, and the stomach, it forms the gastrointestinal tract.