Which epithelial type lines the respiratory tract and contains cilia that move mucus?

• A. Simple columnar epithelium
• B. Ciliated pseudostratified epithelium
• C. Stratified squamous epithelium
• D. Simple squamous epithelium

Answer: (B)

The main idea is mucociliary clearance in the airways, which requires a ciliated, mucus-producing epithelium. In the respiratory tract, the lining is a pseudostratified columnar epithelium that has cilia on its surface and includes goblet cells that secrete mucus. The nuclei of these cells are at different heights, giving a layered appearance, but every cell still touches the basement membrane. The cilia beat in a coordinated way to move the mucus, along with trapped dust and pathogens, upward toward the throat for expulsion or swallowing. That combination of cilia, mucus production, and the tall, columnar cell shape is what enables effective mucus transport in the airways. Other epithelial types either lack cilia or aren’t structured to mobilize mucus—simple columnar epithelium lines the gut and isn’t ciliated; stratified squamous provides abrasion resistance and lacks cilia; and simple squamous lines areas of diffusion like alveoli and vessels, not mucus clearance.