What is the effect of cigarette smoke on airway cilia?

• A. Ciliary beat frequency increases
• B. Reid index unchanged
• C. Cilia are destroyed, reducing mucociliary clearance
• D. Cilia proliferate

Answer: (C)

Cigarette smoke damages the ciliated cells of the airway lining, and over time destroys these cilia, leading to a marked drop in mucociliary clearance. That system normally sweeps mucus and trapped particles out of the airways; when cilia are lost, mucus accumulates, infection risk rises, and conditions like chronic bronchitis can develop. It’s not an increase in beat frequency or cilia proliferation; the key effect is ciliary destruction and impaired clearance. (Smoking also causes mucous gland changes that raise the Reid index, but that relates to mucus production rather than direct ciliary loss.)