What is the primary function of cilia in the airways?

The primary function of cilia in the airways is to clear and defend the conducting airways. Cilia are tiny hair-like structures that line the respiratory tract, and they play a crucial role in maintaining respiratory health. When cilia beat in a coordinated manner, they assist in moving mucus, along with trapped particles and pathogens, upward toward the throat where it can be swallowed or expelled. This mechanism, often referred to as the mucociliary escalator, is essential for removing inhaled irritants and pathogens, thereby helping to prevent infections and clear the airways.

In contrast, while mucus production is indeed important for trapping particles (which involves the function of goblet cells), this is not the direct role of cilia themselves. Similarly, regulating airflow and facilitating gas exchange are functions associated more with the structure of the airways and alveoli rather than the action of cilia. Cilia are specifically adapted to transport substances rather than to regulate airflow or participate directly in gas exchange. Thus, the choice highlighting their role in clearing and defending the conducting airways accurately reflects their primary function.