Small airway of the lung

The small airways of the lung include the terminal and respiratory bronchioles and, in some definitions, the alveolar ducts. These structures have diameters generally less than 2 mm and lack supporting cartilage and submucosal glands[3][5]. Their main functions are conduction of air to the alveoli (where gas exchange occurs), humidification and cleaning via mucociliary clearance, and regulation of airway resistance through smooth muscle contraction[1][3][5]. Small airway dysfunction is implicated in several pulmonary diseases, including asthma, chronic obstructive pulmonary disease (COPD), and bronchiolitis, and is a key site of disease pathology and therapeutic intervention. Drugs such as inhaled corticosteroids, bronchodilators, and mucolytics may be optimized to reach the small airways, although the small airways themselves are not molecular targets but anatomical locations for the drug's site of action.

Other names

Small airwaysPeripheral airwaysDistal airwaysBronchioles (includes terminal and respiratory bronchioles)

Local anti-inflammatory action (corticosteroids); Bronchodilation (β2-agonists, anticholinergics); Mucolytic effects (expectorants, though less direct)