Respiration

In animal physiology, respiration is the function of the respiratory system, which moves oxygen into the organism and carbon dioxide out of the organism. This type of respiration is also called physiologic respiration. The process of moving gases in and out of the organism is also called gas exchange. Gas exchange is facilitated by the presence of respiratory surfaces that have a moist, thin layer of epithelial cells that allow oxygen and carbon dioxide to cross cell membranes. Some aquatic animal species absorb gases directly from water. Arthropods, annelids and fish have gills and vertebrates use lungs for respiration. In lungs, aveoli are the epithelial cells that function in gas exchange and physiologic respiration is commonly known as breathing.

Physiologic respiration provides oxygen to fuel the biochemical process in cells known as cellular respiration and it allows the gaseous waste product of cellular respiration, carbon dioxide, to leave the organism. Cellular respiration is the biochemical breakdown of glucose that produces carbon dioxide, water and cellular energy in the form of ATP, or adenosine triphosphate. Both animal and plant species exhibit cellular respiration physiology.