Small intestine is 6 to 8 m long and highly coiled. It accepts secretions from liver and pancreas. It also secretes some juice from walls of small intestine. In small intestine, digestion of protein, carbohydrates and fats takes place with the help of pancreatic juice and bile juice. Digested food is absorbed in small intestine. There are finger like projections on the inner walls of small intestine, These are called villi. Villi increase the surface area for absorption of digested food. Each villi has a network of blood vessels.
Absorption of digested food takes place on the surface of villi which then goes to blood vessels. Transportation of absorbed food takes place in different parts of body by these blood vessels. Here, it is used for the formation of complex substances. This process is known as Assimilation. Glucose present in cells decomposes into carbon dioxide and water in the presence of oxygen and energy is released. The part of food which is not digested or absorbed is moved to large intestine.
