The small intestines are about 5 1/2 meters long (in an adult) and are separated into three portions with slight differences in function: the duodenum, jejunum, and ileum.  The small intestine is a tube-like structure that is lined with tiny finger-like projections called villi.  This gives the inside surface of the intestines a carpet-like appearance and serves to increase the surface area for absorption of nutrients.  Each villi are covered with even smaller projections called microvilli, increasing the surface area of intestinal wall cells even further.  Enzymes located within the walls of the small intestines help finalize digestion such that nutrients can be absorbed into the blood.  Regular muscle contractions (peristalsis) in the small intestine move food through the intestines and into the colon. Water is a critical component of small intestine function.  Between 1-2 liters of fluid is secreted into the small intestines from the blood.  This makes the intestinal contents easier to absorb.  Almost all of this fluid is resorbed into the blood by the colon.