Why do we Breathe?

We all know instinctively that we must breathe. But why is it necessary for all living plants and animals to breathe? The reason is a very simple one. By breathing we take in air that provides oxygen. Without this gas, no life can exist.

When we exhale the air, it changes. As it makes its way through our system, some of the oxygen is used up, while the amounts of carbon dioxide and water were increased.

Nature keeps up a constant supply of oxygen for our breathing. In fact, from year to year, there is little change in the amounts of oxygen and carbon dioxide we breathe out into the air is taken I by plants. They breathe out oxygen, which we need.

Breathing or respiration is made up of two parts: external and internal breathing. External breathing is what most of us think of when we refer to breathing. It consists of inhaling and exhaling or inspiration and expirations. Inspiration is taking in air through the mouth, the nose, or both. Expiration means sending out air through those same channels, but air that has had about one-fifth of its oxygen exchanged for an equal amount of carbon dioxide. This happens in the lungs.

Internal breathing is the opposite of external. The oxygen taken from the air in the lungs is carried to the tissues of the body by the red cells in the blood. In the tissues this oxygen burns certain food products, making them available for use by the body. The blood takes away the waste products, including water and carbon dioxide. These are returned in the blood to the lungs for exhaling.

Since an exchange of gases (oxygen and carbon dioxide) takes place both in the lungs and in the lungs and in the tissues, a large surface is needed to make this possible. For example, the linings of the lungs of an adult are equal to a space about 36 feet square. This is larger than the ceiling space of one floor of an average house. Much of this are is kept ion reserves, since we might need 8 or 10 times as much oxygen during work as we need at rest. If we need more oxygen, we breathe more deeply or more quickly.
Different creatures breathe at different rates, depending on the oxygen they need. A new born baby breathes about once a second, but at the age of fifteen, breathing is about 20 times a minute. An elephant breathes 10 times a minute; a dog, 25 times a minute.