Air Supply

Abstract

Air contains 20 per cent oxygen. We need oxygen to release energy in aerobic respiration in our cells. We get oxygen from air. We draw air into our bodies when we breathe; Figure 18.1 shows the series of tubes passing from the nose and mouth through the neck and down into the lungs, where oxygen in the air is passed into the blood. Contraction and relaxation of the chest muscles surrounding the lungs result in breathing or ventilation. After air has been breathed into the lungs, air with less oxygen but more carbon dioxide (and water vapour) is breathed out from the lungs.