What is the function of cilia in the respiratory system?

Cilia in the respiratory system play a crucial role in maintaining respiratory health. Their primary function is to trap and move foreign particles, such as dust, pollen, and pathogens, out of the airways. These microscopic hair-like structures line the respiratory tract and work in a coordinated wave-like motion to propel mucus, which captures these particles, upward toward the throat. This process is part of the mucociliary escalator mechanism, which helps keep the airways clear and protects the lungs from infection and irritation.

By effectively removing contaminants from the airway, cilia help maintain normal respiratory function and prevent conditions such as chronic bronchitis or infections like pneumonia. The other options do not accurately describe the specific function of cilia within the respiratory system. For example, while gas exchange does occur in the alveoli, it is not the role of cilia; that function is primarily the responsibility of alveolar cells. Similarly, cilia do not increase airflow or prevent water loss; those functions are managed by other mechanisms within the respiratory system.