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Question
Assertion (A): Alveoli contain an extensive network of blood vessels.
Reason (R): Alveoli are the site where exchange of gases occurs.
Options
Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is not the correct explanation of A.
A is true but R is false.
A is false but R is true.
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Solution
Both A and R are true and R is the correct explanation of A.
Explanation:
The assertion is true because alveoli are enveloped by a dense, massive network of microscopic blood capillaries. The reason is also true and acts as the correct explanation because the biological purpose of this extensive vascular framework is to maximise the speed and efficiency of respiration. Because alveoli are the dedicated primary sites for gaseous exchange, having capillaries tightly wrapped around them ensures that oxygen can immediately diffuse into the blood while carbon dioxide rapidly exits into the lungs.
