The partially digested food is completely digested in the small intestine by the action of pancreatic juice, intestinal juice, and bile.
The pancreatic juice (produced by the pancreas and carried into the small intestine through a duct) contains the enzymes trypsin, amylase, and lipase. Trypsin breaks down the partly digested proteins, amylase changes starch into simple sugars, and lipase splits fats into fatty acids and glycerol.
The intestinal juice is produced by the walls of the small intestine. It has milder digestive effects than the pancreatic juice, but carries out similar digestion.
Bile is produced in the liver, stored in the gall bladder, and flows into the small intestine through the bile duct. Bile contains chemicals that emulsifies fats, thereby helping in their break down and absorption.
When the food is completely digested, it is absorbed by tiny blood and lymph vessels in the walls of the small intestine. It is then carried into the circulation for nourishment of the body.