The small intestine consists of three parts: the duodenum, the jejunum, and the ileum. The entire small intestine is about 6 m long. The duodenum is about 25 cm long (duodenum means 12, suggesting that it is 12 inches long) , the jejunum is about 2.5 m long, and the ileum is about 3.5 m long. Two major accessory glands, the liver and the pancreas, are associated with the duodenum. The small intestine is where the greatest amount of digestion and absorption occur.