Sunday, December 23, 2012

The Human Digestive System

How do we digest food?
            The human body requires a constant supply of food in order to carry out its numerous activities. The food we consume performs two main functions in our body. First, it supplies proteins for the growth of the body and second, it supplies energy to the tissues for the day to day work.
The Human Digestive System
            The process of digestion is very complex and elaborate. Digestion begins at the mouth. When we chew food, the saliva produced in the mouth moistens it. The saliva contains a substance called ptyalin, which converts the starch of the food into simple sugar. This is the first stage of digestion. Therefore we should swallow the food only after chewing it properly.

            After that, the food material passes through the esophagus to the stomach where the gastric juices get mixed with it. The walls of the stomach secret juices containing an enzyme called pepsin and hydrochloric acid. Pepsin breaks down the molecules of proteins into peptones.

            From stomach, the food then enters the small intestine, where it mixes with three other digestive juices- bile, pancreatic juice and intestinal juice. The liver produces bile. Its main function is to digest the fats. The pancreatic juice is basic in nature and neutralizes the acids. It also digests the proteins. The intestinal juice converts sugar into glucose. Here, many enzymes also mix with the food. The digestion of food mainly takes place here. The digested food is them absorbed by the blood vessels present in the wall of small intestine. The remaining waste of the food now goes to the large intestine and is finally excreted out of the body as faeces through the anus.

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