A 25-year-old medical student is examining a section of the trachea. He identifies pseudo-stratified ciliated columnar epithelium with goblet cells. The cilia beat in which direction and what is their primary function?

• A Downward toward the lung alveoli to distribute surfactant
• B Upward toward the larynx to propel mucus (mucociliary escalator) ✓
• C Laterally to mix secretions across the epithelial surface
• D Downward to draw inhaled particles deep into the bronchioles

Explanation

Respiratory epithelium (pseudostratified ciliated columnar with goblet cells) lines the trachea and bronchi. The cilia beat in a coordinated wave toward the larynx (upward), continuously propelling a mucus blanket (with trapped particles and pathogens) toward the pharynx where it is swallowed — the mucociliary escalator. Goblet cells secrete mucus; the cilia move it upward. Primary ciliary dyskinesia (Kartagener syndrome) results in immotile cilia due to absent dynein arms, causing recurrent respiratory infections, bronchiectasis, and situs inversus.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.