Question

Dust particles are less in expired air as compared to the inspired air because

• A. Expired air is released at the alveolar surface.
• B. Expired air is passed through the respiratory tract.
• C. Expired air comes in contact with mucus.
• D. None of the above

Answer 1

Answer: (C)

Expired air comes in contact with mucus.

When one breathes air in at sea level, the inhalation is composed of different gases. These gases and their quantities are Oxygen which makes up 21%, Nitrogen which is 78%, Carbon Dioxide with 0.04% and others with significantly smaller portions. In the process of breathing, air enters into the nasal cavity through the nostrils and is filtered by coarse hairs (vibrissae) and mucous that are found there. The vibrissae filter macroparticles, which are particles of large size. Dust, pollen, smoke, and fine particles are trapped in the mucous that lines the nasal cavities.

So, the correct option is 'Expired air comes in contact with mucus'.