Why Respiration is Necessary for Propagation of Life ?

One can survive without food and water for many hours but survival without the air or oxygen is not possible beyond a few minutes. Every cell in our body is programmed to perform a definite metabolic function necessary for our life. By means of breathing we assimilate oxygen from the air for intracellular metabolism. Through metabolic processes, cells of our body release carbon dioxide (CO₂) and water (H₂O), which are transported away by the circulating blood. Respiration is a two fold process: (1) The interchange of gases in the lungs is called external respiration and (2) The interchange of gases in the tissues is called internal respiration. In the external respiration, oxygen is taken in through the nose and mouth and flows down to the alveoli in the lungs, where it comes in contact with the alveolar capillary membrane and is taken up by the hemoglobin of the red blood cells (RBCs). The oxygenated blood goes to the heart and is further pumped to the various parts of our body. In the lungs, carbon dioxide (CO₂), a waste product of the metabolism is released out through the alveolar capillary membranes and breathed out through the nose and mouth.

The air we breathe in, contains 79% of nitrogen, 20% of oxygen and 0.04 carbon dioxide (CO₂) along with atmospheric water vapors; where as the air we breathe out, contains 79% of nitrogen, 16% of oxygen and 4.04 carbon dioxide (CO₂) along with water vapors released from the alveoli. The total air capacity of our lungs is about 4.5 to 5.0 liters of air and only ¹/₁₀th (500 ml) is generally inspired or expired. The volume of the air under exchange is also termed as tidal air. Our breathing is controlled by two factors: (1) The chemical control of respiration and (2) The nervous control of respiration through the medulla oblongata of our brain. The normal rate of respiration in different age groups is as under:

Status of Age	Respiration Rate per minute
Newborn	38 - 42
Up to 12 months	28 - 32
2 years to 5 years	24 - 26
6 years to 16 years	20 - 24
Adults	10 - 20

The oxygen need of our body varies with the type of activity we perform. Rate of respiration goes up during exercise or running and is considered a vital health parameter for medical fitness evaluation of an individual. As stated above the oxygen (O₂) is the essence of the life force and lack of it may lead to a state of hypoxia or anoxia and brain damage.