Tuesday, April 24, 2012

The Human Digestive System

Alimentary Canal
·       Mouth
·       Pharynx or throat
·       Oesophagus or gullet
·       Stomach
·       Small intestine
·       Large intestine
·       Rectum
·       Anus

Food to a body is like fuel to the machines. Food is needed to
maintain body tissues and is a source of energy for all body functions. A complete food contains all the essential nutrients that are vital for the growth and working of the body. Food, normally, is in the solid state and it is made soluble and absorbable by the chemical reactions of enzymes and digestive juices. The place where food is digested is called digestive tract and from where chemical substances are released, is called digestive gland. They together make the digestive system.

Taste:

 The pleasure of life lies in the different tastes of food. There are granular lumps on the upper surface of our tongue. These are called taste buds. Different tastes buds are connected to the brain by nerve cells which carry the information of taste to the brain. Taste buds are of four kinds which identify sweet, bitter, sour and salty tastes. In the figure below are shown different taste buds and their locations on the tongue.

How food gets digested:

Digestion of food begins in the mouth itself. Chewing makes food soft and breaks it into small pieces. The saliva in the mouth helps break down some carbohydrates into sugar. Saliva also makes the food slippery so that it can slide down the throat or oesophagus easily. A wave like muscle contraction called peristalsis pushes the food down to the stomach. Churning of the stomach changes the food into a semi liquid mass called chime. At this time gastric juices and acids such as hydrochloric acid start digesting the food and help to kill the bacteria in the food. Liquid food now goes int o the small intestine. Here some more enzymes are added to the food most of the food is broken down in the small intestine into its simplest form-----sugar, amino acids and fat. It takes about five hours. The nutrients of the food are absorbed by millions of tiny finger like projections called villi. From there the nutrients are absorbed into the blood and are transported to every cell.

          From the small intestine food goes to the large intestine. The small intestine is about 6.5m long while large intestine is 1.8m long. As it passes into the large intestine, water is removed and the waste product is passed out of the body as faeces through the anus. The faeces contain undigested food, cell, bile, salt ad spleen salts. 
The Digestive System
                                                   Taste Buds and The Tongue

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