[Pulmonary surfactant in the respiratory tract]

Pulmonary surfactant is a surface active material able to reduce surface tension at the alveolar and bronchiolar air-liquid interface. It plays an important role in conductive as well in peripheral airways and that is why surfactant dysfunction is thought to contribute to pathomechanisms of pulmonary diseases with bronchial obstruction. Airway surfactant originates mainly from alveoli and some components (specific proteins SP-A, SP-B and SP-D) are synthetized and secreted also by non-ciliated cells of the airway mucosa. In comparison to alveolar surfactant the bronchiol one has the same composition, with lower amount of surfactant proteins. Surfactant has following functions in airways: stabilisation of small airways, role in mucociliary and non-ciliary transport, immunomodulation, barrier function and antiedematous function. Ability of pulmonary surfactant to influence wall thickness and diameter of airways indicates possible role of its quantitative and/or qualitative changes in the pathogenesis of asthma, chronic obstructive pulmonary disease and others.