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Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a biological membrane that forms the boundary between an organism and its extracellular environment.
Gas exchange in the lungs occurs in millions of small air sacs; in mammals and reptiles, these are called alveoli, and in birds, they are known as atria. These microscopic air sacs have a very rich blood supply, thus bringing the air into close contact with the blood. [ 2 ]
The right-to-left shunt is an abnormal blood circulation that enables deoxygenated blood to pass from the right side to the left side of the heart and skips the lungs. Thus, no oxygenation occurs, and reduced gas exchange results in hypoxemia as fresh oxygen cannot reach the shunted blood. [18]
Exchange of gases in the lung occurs by ventilation and perfusion. [1] Ventilation refers to the in-and-out movement of air of the lungs and perfusion is the circulation of blood in the pulmonary capillaries. [1] In mammals, physiological respiration involves respiratory cycles of inhaled and exhaled breaths.
This is known as outgassing, and occurs during decompression, when the reduction in ambient pressure or a change of breathing gas reduces the partial pressure of the inert gas in the lungs. [ 2 ] The combined concentrations of gases in any given tissue will depend on the history of pressure and gas composition.
The actual values in the lung vary depending on the position within the lung. If taken as a whole, the typical value is approximately 0.8. [4] Because the lung is centered vertically around the heart, part of the lung is superior to the heart, and part is inferior. This has a major impact on the V/Q ratio: [5] apex of lung – higher; base of ...
Oxygen-deprived blood from the superior and inferior vena cava enters the right atrium of the heart and flows through the tricuspid valve (right atrioventricular valve) into the right ventricle, from which it is then pumped through the pulmonary semilunar valve into the pulmonary artery to the lungs. Gas exchange occurs in the lungs, whereby CO ...
These changes ultimately result in an increased exchange of oxygen and carbon dioxide, which is accompanied by an increase in metabolism. [2] Respiratory adaptation is a physiological determinant of peak endurance performance, and in elite athletes, the pulmonary system is often a limiting factor to exercise under certain conditions.