Food is needed for growth. It acts as a fuel for the production of heat and energy. The digestive system receives the food and breaks it down into simpler components so that it may be used in the body. The entire process of the reception of food and its breaking down into simpler components is called digestion. The human digestive system consists of alimentary canal and its glands. The major parts of the digestive system are: mouth, oesophagus (food pipe), stomach, small intestine, large intestine, rectum, liver and pancreas. The human alimentary canal is basically about 9 metres long tube that runs from the mouth to the anus.
Digestion of Food
The food that we eat is composed of complex components. These components are needed to be broken down into simpler form so that they may be used in the body. The entire process of breaking down the complex nutrients into simpler form is called digestion. The process of digestion starts from the mouth and ends in the small intestine. When the food is converted into simpler form, it can be absorbed into the bloodstream. Once nutrients are taken up by the bloodstream, they can be distributed to and used by the body cells.
The digestion process:
a. Food enters the body through the mouth where it is mechanically broken down into smaller form. The masticated form of food is called bolus. The enzymes secreted by the salivary glands start the process of digestion.
b. The food then travels to the pharynx and the oesophagus. From the oesophagus, food enters the stomach.
c. In the stomach, the food is churned and the digestion of complex nutrients takes place. The stomach is filled with acid that activates the enzymes, breaks down the food further and kills the germs. The semi-digested food that leaves the stomach is referred as chyme.
d. The chyme enters the small intestine where it is digested completely and the nutrients are absorbed.
e. The food devoid of nutrients then enters the large intestine where excess water is absorbed and the semi-solid residue is expelled out of the body through the rectum.
