Mucociliary clearance

Mucociliary clearance (MCC), also referred to as mucociliary escalator, derived from mucus, cilia (cilia of the respiratory epithelium in the respiratory tract) and clearance describes the self-clearing mechanism of the bronchi. Its effectiveness relies on the correct properties of the mucus produced and of the number and quality of the cilia present in the airway lining. Mucociliary clearance (MCC), also referred to as mucociliary escalator, derived from mucus, cilia (cilia of the respiratory epithelium in the respiratory tract) and clearance describes the self-clearing mechanism of the bronchi. Its effectiveness relies on the correct properties of the mucus produced and of the number and quality of the cilia present in the airway lining. In the respiratory tract, from the trachea to the respiratory bronchioles, the epithelial lining is of respiratory epithelium that is ciliated. The cilia are hair-shaped structures on its surface. The cilia are surrounded by mucus, or epithelial lining fluid (ELF), the composition of which is tightly regulated; the mucus helps maintain epithelial moisture and traps particulate material and pathogens moving through the airway and determines how well mucociliary clearance works.:234 Within the thin fluid film of mucus the cilia act out movements coordinated in direction towards the pharynx. Thereby the viscous film of mucus including its freight is transported off in direction towards the mouth, where it is either swallowed or expelled via coughing. Important for good mucociliary clearance are the number of cilia, their structure, activity, and coordinated movement. Optimum functionality of mucociliary clearance presupposes a temperature of 37.0 °C (98.6 °F)  and an absolute humidity of 44 mg/dm³ corresponding to a relative humidity of 100%. Under the condition of insufficient temperature and humidity, after a short time the ciliary cells suspend their transport function. Under such circumstances, bacterial germinal colonization is facilitated. Pulmonary infections and damaging of the pulmonic tissues may be the consequence. High humidity enhances mucociliary clearance. Two methods of supporting this are provided by active and passive respiratory gas humidifiers, which in particular are used in mechanical ventilation.