Which of the following best describes the function of the mucociliary escalator?

• A. Facilitates gas exchange in the alveoli
• B. Expels mucus and trapped particles from the airways
• C. Delivers oxygen to lung cells
• D. Regulates pulmonary blood pressure

Answer: (B)

The mucociliary escalator plays a crucial role in the respiratory system's defense mechanism. It refers to the combined action of cilia, which are tiny hair-like structures on the surface of airway epithelial cells, and mucus produced by goblet cells and submucosal glands. The primary function of the mucociliary escalator is to trap inhaled particles, pathogens, and debris within mucus, which is then moved upward through coordinated ciliary movements towards the pharynx. This process helps to expel mucus along with its trapped contents from the airways, keeping the respiratory tract clear and preventing infections and irritations from inhaled substances.

Other choices describe functions that do not pertain to the mucociliary escalator. Gas exchange occurs at the alveolar level and involves the diffusion of oxygen and carbon dioxide; delivering oxygen to lung cells relates to the role of red blood cells and hemoglobin; and regulating pulmonary blood pressure pertains to the cardiovascular aspects of lung function rather than the cleaning mechanism provided by the mucociliary escalator. Therefore, the correct answer is supported by the specific role that the mucociliary escalator has in maintaining airway hygiene and respiratory health.