Which of the following is a common method of filtering bacteria and particles in the respiratory system?

• A. Mucociliary escalator
• B. Gas exchange
• C. Ciliary action
• D. Phonation

Answer: (A)

The mucociliary escalator is a significant defense mechanism in the respiratory system, playing a critical role in filtering out bacteria and particles. It consists of cilia—tiny hair-like structures—on the surface of the respiratory epithelial cells, which continuously beat in a coordinated fashion. This action helps to propel mucus, which traps inhaled particles like dust, pollen, and pathogens, upward toward the throat. From there, the mucus can be swallowed or expelled through coughing, thereby maintaining a clear airway and preventing infections.

Gas exchange, on the other hand, refers to the process of oxygen and carbon dioxide being exchanged in the alveoli and does not directly filter out particles or bacteria. While ciliary action is a component of the mucociliary escalator, it does not encompass the entire process, which also includes mucus production. Phonation is related to sound production and does not have a role in filtering or protecting the respiratory system. Therefore, the mucociliary escalator stands out as the primary method for filtering contaminants in the respiratory tract, effective in keeping the lungs clear and reducing the risk of infection.