In order for external respiration to take place,the alveoli must have a higher oxygen concentration and a lower carbon dioxide concentration than the blood in the lung capillaries.

Question

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This is because oxygen diffuses from an area of high concentration (in the alveoli) to an area of low concentration (in the blood), while carbon dioxide diffuses from an area of high concentration (in the blood) to an area of low concentration (in the alveoli). Therefore, for the exchange to occur, there must be a concentration gradient in favor of diffusion.

In Order for External Respiration to Take Place,the Alveoli Must