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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.
The morphologies of the individual air sacs also vary among bird taxa. [7] In birds, gas exchange and volume change do not occur in the same place. [2] While gas exchange occurs in the parabronchi in the lungs, the lungs do not change volume much during respiration. [9] Instead, voluminous expansion occurs in the air sacs.
Each pair of dorso-ventrobronchi is connected by a large number of parallel microscopic air capillaries (or parabronchi) where gas exchange occurs. [59] As the bird inhales, tracheal air flows through the intrapulmonary bronchi into the posterior air sacs, as well as into the dorsobronchi (but not into the ventrobronchi whose openings into the ...
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]
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 ...
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 ...
Birds have a very efficient system for diffusing oxygen into the blood; birds have a ten times greater surface area to gas exchange volume than mammals. As a result, birds have more blood in their capillaries per unit of volume of lung than a mammal. [ 111 ]
As birds have a longer and wider trachea than mammals the same size, they have a disproportionately large anatomic dead space, reducing the airway resistance. This adaptation does not impact gas exchange because birds flow air through their lungs - they do not breathe in and out like mammals. [7]