- A fluid secreted by the cells of the alveoli (the tiny air sacs in the lungs) that serves to reduce the surface tension of pulmonary fluids; surfactant contributes to the elastic properties of pulmonary tissue. In more technical terms, a surfactant is a surface active agent, the best known example being the lung surfactant that is produced shortly before birth and makes the alveolar surfaces hydrophobic and prevents the lung from filling with water.
* * *1. A surface-active agent, including substances commonly referred to as wetting agents, surface tension depressants, detergents, dispersing agents, emulsifiers, quaternary ammonium antiseptics, etc. 2. Those surface-active agents forming a monomolecular layer over pulmonary alveolar surfaces; lipoproteins that include lecithins and sphygomyelins that stabilize alveolar volume by reducing surface tension and altering the relationship between surface tension and surface area. [surface active agent]- zwitterionic s. a dipolar s..
* * *sur·fac·tant (.)sər-'fak-tənt, 'sər-. n a surface-active substance specif a surface-active lipoprotein mixture which coats the alveoli and which prevents collapse of the lungs by reducing the surface tension of pulmonary fluidssurfactant adj
* * *n.a wetting agent. Pulmonary surfactant, secreted by type II pneumocyte, is a complex mixture of compounds (including lipids, protein, and carbohydrates) that prevents the air sacs (alveoli) of the lungs from collapsing by reducing surface tension. In its absence, as in the immature lungs of premature babies, atelectasis and respiratory distress syndrome will develop.
* * *sur·fac·tant (sər-fakґtənt) 1. surface-active agent. 2. in pulmonary physiology, a mixture of phospholipids (chiefly lecithin and sphingomyelin) secreted by the alveolar type II cells into the alveoli and respiratory air passages, which reduces the surface tension of pulmonary fluids and thus contributes to the elastic properties of pulmonary tissue.
Medical dictionary. 2011.