The small intestine is a long tube that is approximately 18 feet long (6 meters). The small intestine is called small because the diameter or the width of the tube is much less than the large intestine. The parts of the small intestine include the duodenum, jejunum and the ileum. The duodenum is a segment of intestine between the stomach and the jejunum that is very active in digestion where many different enzymes mix from the stomach, liver, gallbladder and pancreas. The small intestine is the location in the body where the majority of the nutrients from ingested food are absorbed. Whereas the stomach is responsible for the churning and mechanical breakdown of food, the small intestine is very important for absorption. Digested food passes through the wall of the intestine into the blood vessels which then distribute the nutrition first to the liver and then through the rest of the body.