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How do mucus and cilia in the nasal cavity trap inhaled particles?

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Illustration showing different animals and their respiratory organs: a spider with book lungs, a chicken with lungs, a sponge with labeled inflow and outflow pores, a fish with gills, and a caterpillar with spiracles. — Respiratory system Different methods of respiration in animals.

In the nasal cavity, the respiratory mucosa plays a critical role in cleaning inhaled air by trapping foreign debris, such as dust, soot, carbon, and bacteria.12

This protective mechanism relies on two primary components:

Mucus: Secreted by glands within the membrane wall, this viscous fluid acts as a sticky trap. It captures small inhaled particles, preventing them from entering deeper into the respiratory tract or reaching delicate tissues.132
Cilia: These are fine, hairlike projections found on the surface of the respiratory epithelium. They work in conjunction with the mucus to collect debris.2

While the nasal cavity uses these structures to filter air, a similar process occurs throughout the conducting airways of the lungs, where the mucociliary escalator uses synchronized, rhythmic ciliary beats to move the mucus-trapped particles toward the pharynx to be swallowed. Together, these structures ensure that air is cleaned, warmed, and moistened before it reaches the gas-exchange areas of the lungs.452