Question

The figure given below shows a small part of human lung where exchange of gases takes place. In which one of the options given below, the one part A, B, C or D is correctly identified along with its function?
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• A. B : red blood cell - transport of CO₂ mainly
• B. D : capillary wall - exchange of O₂ and CO₂ takes place here.
• C. A : alveolar cavity - main site of exchange of respiratory gases
• D. C : arterial capillary – passes oxygen to tissues

Answer 1

Answer: (C)

In the given figure the exchange of respiratory gases occurs in alveolar cavity.
The diffusion membrane is made up of three major layers namely, the thin squamous epithelium of alveoli, the endothelium of alveolar capillaries and the basement substance in between them. However, its total thickness is much less than a millimetre. Therefore, all the factors in our body are favourable for diffusion of O₂ from alveoli to tissues and that of CO₂ from tissues to alveoli.