Intestinal villi are small, finger-like projections that protrude from the walls of the small intestine. The villi increase the absorptive surface of the intestine and ensure efficient absorption of nutrients. The villi have microvilli projecting from their outer epithelial walls.
The villi also have digestive enzymes on their surface. Digested food passes into the villi through diffusion. Villi have very thin walls that are about one cell thick, and this helps ensure superior absorption. The villi are connected to blood vessels to allow nutrients to be carried away by the blood. Villus capillaries collect the simple sugars and amino acids taken in by the villi into the bloodstream. Villus lacteals are lymph capillaries that collect the absorbed fatty acids and glycerol and take it to the rest of the body through the lymph fluid.
Villi also help the food to move along the digestive tract. Food takes three to six hours to move through the small intestine. The small intestine has three parts, the duodenum, jejunum and ileum. Most of the digestion and absorption takes place in the small intestine. After that, the food moves to the large intestine, where most of the water and electrolytes are absorbed and fecal matter is stored for expulsion.