The main function of the digestive system is digestion of food and absorption of nutrients. Digestion in humans begins in the mouth. It involves the mechanical breakdown of food by the teeth and the breakdown of food by the digestive enzymes present in saliva. The food is then formed into a bolus and swallowed. It goes down the esophagus by peristalsis and enters the stomach. In the stomach gastric enzymes are released and they breakdown the food further. The food that is partially digested now enters the duodenum as chyme. The major part of digestion happens in the small intestines. Digestion in the small intestines occurs due to intestinal juices, pancreatic juices and bile.
Absorption is the process by which the digested food pass
through the intestinal wall into the blood vessels. Most of the absorption of
the nutrients of digested food takes place in the small intestines. The walls
of the small intestines are lined by villi with numerous micro villi on their
epithelial cells. The numerous villi are responsible for absorption of
nutrients and the numerous micro villi increase surface area of absorption of
these nutrients. Absorption of water occurs in the large intestines.
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