THE PULMONARY SURFACTANT SYSTEM - BIOLOGICAL FUNCTIONS, COMPONENTS, PHYSICOCHEMICAL PROPERTIES AND ALTERATIONS DURING LUNG-DISEASE

The alveolar epithelium in the lung is covered with a liquid, the alve olar lining layer. This alveolar lining layer consists of an aqueous s ubphase covered by a film of pulmonary surfactant. The surfactant film reduces the air-liquid interfacial tension, thereby preventing alveol ar collapse and preserving the gas exchange surface. The aqueous subph ase provides a storage medium for surfactant components. Into this med ium surfactant components are secreted from type II cells, adsorb to a nd desorb from the air-liquid interface, change their morphological st ructures and interact with cells of the host defense system, e.g. alve olar macrophages. Alterations of the pulmonary surfactant system occur in clinical conditions including the respiratory distress syndrome of the premature newborn and the adult. This review summarizes biologica l functions, components and physicochemical properties of the pulmonar y surfactant system and describes alterations of the system found duri ng respiratory distress syndrome of the adult.