Question

The actual site of gaseous exchange in the human respiratory system is

• A. Trachea
• B. Bronchioles
• C. Alveoli
• D. All the above

Answer 1

The correct option is C Alveoli

The primary function of the respiratory system is to exchange oxygen (O${}_2$) and carbon dioxide (CO${}_2$). The external nostrils up to the terminal bronchioles constitute the conducting part whereas the alveoli and their ducts form the respiratory or exchange part of the respiratory system.

The conducting part transports the atmospheric air to the alveoli. Exchange part is the site of actual diffusion of O${}_2$ and CO${}_2$ between blood and atmospheric air. The alveolus is richly supplied with blood capillaries which allow the exchange of gases through it.

So, the answer is C.