Mukociliar

Mukociliar, commonly referred to as mucociliary clearance, is the physiological mechanism by which the respiratory tract removes inhaled particles, pathogens, and debris from the airways. It relies on the coordinated action of ciliated epithelial cells, mucus-producing goblet cells, and submucosal glands, all lining a moist airway surface.

Airway surface liquid is organized into two layers: a gel-like mucus layer that traps inhaled material, and a periciliary liquid layer in which the cilia beat. The cilia beat in a coordinated, metachronal rhythm, transporting the mucus layer upward toward the pharynx at a steady rate. This movement is powered by energy from ATP and is regulated by ion transport and hydration of the airway surface.

Mucus contains mucins, including MUC5AC and MUC5B, which give it viscoelastic properties that trap particles. The airway surface liquid is maintained by ion channels such as CFTR; proper hydration is essential for effective clearance. When this system functions well, most inhaled bacteria, viruses, and pollutants are removed before they can cause infection.

Impairment of mucociliary clearance occurs in various conditions, including primary ciliary dyskinesia, chronic mucus hypersecretion in smokers, cystic fibrosis, and chronic obstructive pulmonary disease. Diminished clearance increases the risk of respiratory infections and inflammation.

Clinical relevance and management include assessing mucociliary function, for example with saccharine transit time tests, and strategies to support clearance. Treatments focus on hydration and humidification, airway clearance techniques, inhaled hypertonic saline, and mucolytics such as N-acetylcysteine, along with management of underlying diseases and avoidance of irritants.