[The surfactant system of the lung as a functional unit]

Morphological, biochemical and biophysical data indicate that the pulmonary surfactant system of the lung has to be considered as a functional unit from the alveoli to the trachea. In the nonciliated part of the air passages the surfactant assures the stability of the small airways and contributes to the transport processes. In the ciliated part of the air passages the surfactant supports indirectly the optimal transport of mucus due to its anti-glue properties. Any deterioration in the surfactant system results in functional consequences for lung mechanics and bronchial clearance mechanisms as discussed for RDS and COLD. Stimulation of surfactant synthesis and surfactant replacement can be regarded as new aspects for therapy.