The diagram below shows a part of the respiratory system in humans. Which option shows the correct labelling of ' a ' and ' b ' and the function of ' b '?

Correct option is D

Sol: The correct answer is (d) a - Bronchioles, b - Alveoli (exchange of gases)

In the human respiratory system, a - Bronchioles, and b - Alveoli (exchange of gases). The alveoli are small air sacs where the exchange of gases (oxygen and carbon dioxide) occurs between the lungs and the blood. Bronchioles are the smaller airways that lead to the alveoli.

Information booster:

​Bronchioles:

• Small branches of the bronchi.
• No cartilage, only smooth muscle.
• Lead to alveoli for gas exchange.
• Regulate airflow by constricting or dilating.
• Found within the lungs.

​Alveoli:

• Tiny air sacs at the end of bronchioles.
• Surrounded by a network of capillaries.
• Main site for gas exchange (oxygen in, carbon dioxide out).
• Have very thin walls to allow diffusion of gases.
• Millions of alveoli provide a large surface area for exchange.