Breathing (hereinafter — “D.”; this article is in russian — Дыхание) — is a set of processes that provide the flow of oxygen into the body and the release of carbon dioxide (external D.) and the use of oxygen by cells and tissues for the oxidation of organic substances with the release of the energy contained in them, necessary for life (tissue respiration, cellular D.). Oxygen-free way of energy release is peculiar only to a small group of organisms-the so-called anaerobes; during the evolution of the release of energy as a result of D. the vast majority of organisms became the main process, and anaerobic reactions remained mainly as intermediate stages of metabolism.

The breath of animals and humans

In protozoa, sponges, coelenterates and some other organisms O₂ diffuses directly through the surface of the body. With the complication of the organization and increase in body size there are special breathing organs, as well as the circulatory system, which circulates the liquid — blood or hemolymph containing substances that can bind and carry O₂ and CO₂ (see hemoglobin). In insects, O₂ enters the tissues from the system of air — borne tubes-trachea. In aquatic animals, using dissolved in water O₂, respiratory gills are provided with a rich network of blood vessels. In this case, O₂ dissolved in water diffuses into the blood circulating in the vessels of Gill slits. In many fish, the intestinal D. plays a significant role, in which air is swallowed and O₂ enters the blood through the blood vessels of the intestine; some role In D. fish also plays a swimming bubble; many animals living in the water exchange of gases (mainly CO₂) occurs through the skin.– Далее –

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