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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 reptiles still occurs in alveoli, but reptiles do not possess a diaphragm, therefore ventilation occurs via a change in the volume of the body cavity which is controlled by contraction of intercostal muscles in all reptiles except turtles. In turtles, contraction of specific pairs of flank muscles governs inspiration or ...
This blood gas barrier is extremely thin (in humans, on average, 2.2 μm thick). It is folded into about 300 million small air sacs called alveoli [23] (each between 75 and 300 μm in diameter) branching off from the respiratory bronchioles in the lungs, thus providing an extremely large surface area (approximately 145 m 2) for gas exchange to ...
The roof of the lung is highly vascularised, and it is through this surface that gas exchange occurs. The majority of pulmonates are fully terrestrial. Most have the typical lung arrangement described above, but in the Athoracophoridae , the mantle cavity is replaced by a series of blind tubules, while the Veronicellidae respire through their ...
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 ...
Countercurrent exchange means the flow of water over the gills is in the opposite direction to the flow of blood through the capillaries in the lamellae. The effect of this is that the blood flowing in the capillaries always encounters water with a higher oxygen concentration, allowing diffusion to occur all the way along the lamellae.
Cutaneous respiration, or cutaneous gas exchange (sometimes called skin breathing), [1] is a form of respiration in which gas exchange occurs across the skin or outer integument of an organism rather than gills or lungs. Cutaneous respiration may be the sole method of gas exchange, or may accompany other forms, such as ventilation.
Channels are contiguous if effective exchange is to occur (i.e. there can be no gap between the channels). In the cocurrent flow exchange mechanism, the two fluids flow in the same direction. As the cocurrent and countercurrent exchange mechanisms diagram showed, a cocurrent exchange system has a variable gradient over the length of the exchanger.