Question

The diagram 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.

• A. C: Arterial capillary - passes oxygen to tissues
• B. A: Alveolar cavity - main site of exchangeof respiratory gases
• C. D: Capillary wall - exchange of $H_{2}O$and $C{O}_2$ takes place here
• D. B: Red blood cells - transport of $C{O}_2$ mainly

Answer 1

The correct option is B A: Alveolar cavity - main site of exchangeof respiratory gases


Alveoli are the primary sites of exchange of gases. Exchange of gases also occur between blood and tissues. $O_2$ and $C{O}_2$ are exchanged in these sites by simple diffusion mainly based on pressure/concentration gradient.