Bronchial mucus transport.

Effective clearance of inhaled particles requires mucus production and continuous mucus transport from the lower airways to the oropharynx. Mucus production takes place mainly in the peripheral airways. Mucus transport is achieved by the action of the ciliated cells that cover the inner surface of the airways (mucociliary transport) and by expiratory airflow. The capacity for mucociliary transport is highest in the peripheral airways, whereas the capacity for airflow transport is highest in the central airways. In patients with airways disease, mucociliary transport may be impaired and airflow transport may become the most important mucus transport mechanism.