What is a key function of cilia in the respiratory system?

Cilia play a crucial role in the respiratory system by serving as a defense mechanism to trap and expel debris. These hair-like structures line the respiratory tract and are covered in a layer of mucus. When inhaled air passes through the respiratory system, cilia continuously beat in a coordinated manner to move mucus, along with trapped particles, pathogens, and dust, upward toward the throat. This process is part of the mucociliary escalator, which helps keep the airways clear and free from irritants, thereby maintaining respiratory health. This function is vital for preventing infections and ensuring that the lungs remain clear for optimal gas exchange.

The other options do not accurately describe the primary function of cilia in this context. Gas exchange primarily occurs in the alveoli, and while cilia do help maintain a conducive environment for gas exchange by keeping the airways clear, they do not directly participate in the diffusion of gases. Sound production is mainly related to the vocal cords and the larynx rather than the respiratory tract's cilia.