肺泡表面有极薄的一层液体,它衬在肺泡内壁形成一层液体膜。物质分子之间存在着相互吸引的作用力,但气体中分子数比同体积液体中的分子数少得多,因而肺泡气液界面的表面分子所受到的周围吸引力是不均衡的,有使表面收缩的倾向,这样就使液体膜表面好象一个拉紧的弹性膜、形成一种肺泡向中心收缩的力量,这就叫做肺泡表面张力(Surface ten-sion)。肺泡表面张力是构成肺回缩力的主要成分,它 Alveolar surface has a thin layer of liquid, which lined the alveolar wall to form a liquid film. There are mutual attractive forces between material molecules, but the molecules in the gas are much less than those in the same volume of liquid, so the attractiveness around the surface molecules in the gas-liquid interface is not balanced, The tendency of the surface to contract is such that the surface of the liquid membrane acts as a taut elastic membrane, forming a force that contracts the center of the alveoli, which is called Surface ten-sion. Alveolar surface tension is the main component of pulmonary retraction force, it