Respiratory System

Respiration and Breathing

How is air cleaned before reaching the lungs?

There are many ways by which air is cleansed before it reaches the lungs. As air is inhaled through the nose, the outer part of the nostril has visible hairs (vibrissae) that filter larger particles. In addition, the nasal cavity has a mucous lining that traps smaller particles or microorganisms. The mucus then flows toward the pharynx, where it is swallowed; any trapped microbes are usually killed when exposed to the acidic conditions in the stomach. The cells lining the respiratory system have cilia (tiny, oar-like appendages) on the surface that act as an additional filter to trap debris.


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