Gas exchange or respiration in humans is the means by which getting oxygen from air into the blood and carbon dioxide out of the blood into the air. Humans must exchange these gases with the environment because oxygen is essential for cells, which use this vital substance to release the energy needed for cellular activities. In addition to supplying oxygen, carbon dioxide needs to be removed in order to prevent the buildup of this waste product in the body tissues. As breathing is the act or process of respiration, it consists of two phases, inspiration and expiration. …
