BREATHING

If our bodies did not have oxygen, we would die. We need to combine this gas with the food we digest, to turn it into energy. Oxygen gets into the body through the lungs, which take it from the air. Our lungs are situated on either side of the heart, behind the protective cage formed by the ribs. We also have to get rid of carbon dioxide and other waste products. When we breathe, we take in oxygen and breathe out carbon dioxide.

The air goes up the nose, then down the throat and windpipe into the lungs. The long journey through moist tubes helps to remove dust. Most of the dust is trapped in the nose. Blow your nose after you have been in a dusty place, and you will realize what a good filter it is. The air is also warmed on its way to the lungs. When you breathe in, the diaphragm moves down. The ribs also move out and up. This creates a vacuum, and air rushes in to fill the space. A tiny air sac or alveolus, through which oxygen passes from the air in the lungs into the blood  in the capillaries. This is possible because the air sac and capillary walls are thin. Carbon dioxide and other waste materials also pass out through them into the air.

·        It is better to breathe through the nose than the mouth. This is because there are hairs in the nose which can trap bacteria before they reach the lungs.

·        Of the total amount of oxygen taken in by the body, one quarter is needed by the brain.