What is the function of the mucociliary escalator?

• A. Move mucus towards the pharynx and clean respiratory surfaces
• B. Produce mucus
• C. Exchange gases in alveoli
• D. Filter blood

Answer: (A)

The mucociliary escalator is a defense mechanism that clears the airway by transporting mucus trapped with debris upward toward the pharynx. The lining of the trachea and bronchi has ciliated cells that beat in a coordinated fashion, moving the mucus layer from the lungs up to the throat where it can be swallowed or expelled. This keeps the respiratory surfaces clean and protects the lower airways from infection and irritation. Mucus production itself is done by goblet cells, not by the transport system. Gas exchange happens in the alveoli, and blood filtration is accomplished by other organs such as the kidneys, so those options don’t describe the escalator’s function.