The small intestine is about 5 m long and its diameter is about 35 mm. It stretches between the duodenum and the colon (the first part of the large intestine) and represents the main area of absorption of nutrients into the bloodstream.
Like the stomach, the colon is also constantly on the move: the peristalsis waves of contractions of the intestinal wall, which are automatically controlled by the nerve network, push the food down the intestine. In the small intestine, the process of digestion of small particles that begun in the stomach and the duodenum continues, assisted by additional enzymes. Molecules then pass through the thin mucous membrane of the intestine into the bloodstream, and then into the liver for deposit and distribution.
In order to absorb as much food as possible from the small intestine, the inner side of its wall is covered with small finger-like projections called villi. With their large surface, the villi ensure maximum absorption of nutrients into the body.