ANIMAL PHYSIOLOGY
GAS EXCHANGE IN HUMANS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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They occur in all animals because they are needed for gas exchange.
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They have a higher oxygen concentration than air in the atmosphere to increase the rate of diffusion
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They have walls that are one cell thick for faster diffusion.
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They are small so keep the gases inside them more concentrated.
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Detailed explanation-1: -a) The alveoli wall (and the capillary wall) is only one cell thick so there is only a short distance over which diffusion takes place (short diffusion pathway) so there is a faster rate of diffusion of oxygen from alveoli into the blood.
Detailed explanation-2: -The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and breathing out. Oxygen breathed in from the air passes through the alveoli and into the blood and travels to the tissues throughout the body.
Detailed explanation-3: -The walls of the alveoli are very thin. This lets oxygen and CO2 pass easily between the alveoli and capillaries, which are very small blood vessels. Oxygen can pass from the alveoli to the capillaries because the concentration of oxygen is lower in the capillaries than in alveoli.
Detailed explanation-4: -Adaptations of the alveoli: Permeable walls-allow gases to pass through. Extensive blood supply-ensuring oxygen rich blood is taken away from the lungs and carbon dioxide rich blood is taken to the lungs.
Detailed explanation-5: -Alveoli have the following key features to maximise gas exchange: A huge combined surface area. Moist, thin walls to maximise diffusion. Millions of tiny blood vessels called capillaries just behind these walls.