How do tiny moving cilia help clear the airways?

Air brings oxygen into the body, but it can also carry dust and microorganisms. Mucus along many airways traps some of these particles before they can travel farther into the respiratory system.

Beneath that mucus are cells with tiny moving projections called cilia. Their coordinated strokes push the mucus toward the throat. Many small movements together create a slow transport system across the airway surface.

At the throat, mucus can be swallowed or expelled. This movement continually removes some trapped material. The cilia are living cell structures supplied with energy; they are not loose hairs blown back and forth by breathing.

The system works with other defenses, including coughing and immune responses. If cilia cannot move effectively, mucus can accumulate and infections become more likely. Clear breathing therefore depends partly on coordinated microscopic motion along surfaces that are normally out of sight.