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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.
In fact, the rate of gas diffusion is regarded as one of the main limiting factors (along with weight of the exoskeleton) that limits the size of insects. [2] Periods in Earth's ancient history, however, such as the Carboniferous , featured much higher oxygen levels (up to 35%) that allowed larger insects, such as meganeura , along with ...
Ventilation (or breathing) is the air movement between the lungs and the atmospheric air, facilitating gas exchange. The air rushes into the lungs through inhalation (inspiration) and is pushed out through exhalation (expiration). [2]
Gas exchange takes place in the gills which consist of thin or very flat filaments and lammellae which expose a very large surface area of highly vascularized tissue to the water. Other animals, such as insects, have respiratory systems with very simple anatomical features, and in amphibians, even the skin plays a vital role in gas exchange.
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.
The primary purpose of breathing is to refresh air in the alveoli so that gas exchange can take place in the blood. The equilibration of the partial pressures of the gases in the alveolar blood and the alveolar air occurs by diffusion. After exhaling, adult human lungs still contain 2.5–3 L of air, their functional residual capacity or FRC ...
These factors influence the transport of dissolved gases by diffusion and perfusion, and therefore affect the rate of uptake and elimination. [64] There are also effects due to bubble presence such as microparticles, oxidative stress, neutrophil activation, and endothelium damage. [60]
Diffusing capacity of the lung (D L) (also known as transfer factor) measures the transfer of gas from air in the lung, to the red blood cells in lung blood vessels. It is part of a comprehensive series of pulmonary function tests to determine the overall ability of the lung to transport gas into and out of the blood.