Tracheal Cilia and Mucus: Direction of Mucociliary Clearance

Direction of Flow

False. The mucociliary escalator moves mucus and trapped particles upward (cephalad) toward the pharynx, not downward.

Mechanism

• Ciliated pseudostratified columnar epithelium lines trachea and bronchi.
• Coordinated ciliary beating (effective stroke upward, recovery stroke downward) propels mucus layer at ~1–2 cm/min.
• Mucus reaches oropharynx → swallowed (destroyed by stomach acid) or expectorated.

Clinical Relevance

• Impaired in smoking, cystic fibrosis, primary ciliary dyskinesia, intubation, anesthesia → mucus stasis → infection.
• Postural drainage and chest physiotherapy assist clearance in disease.