肺泡内壁由Ⅰ型肺泡细胞和Ⅱ型肺泡细胞构成。Ⅱ型细胞能分泌一种表面活性物质(surf)。它是由一些在体温下有高度表面活性,即能降低表面张力的物质组成的。肺泡表面有一层液体,液体与肺泡内气体之间形成液-气界面,故有表面张力,能使液层面积缩小,亦即使肺泡缩小。表面张力越大,肺泡半径越小,回缩的压力就越大。Surf The alveolar wall consists of type I alveolar cells and type II alveolar cells. Type II cells can secrete a surface active substance (surf). It is composed of some substances that have a high degree of surface activity at body temperature, that reduces the surface tension. Alveolar surface layer of liquid, liquid and alveolar gas between the formation of liquid - gas interface, so the surface tension, can make the liquid layer area reduced, even if the alveolar contraction. The larger the surface tension, the smaller the alveolar radius, the greater the pressure of retraction. Surf