About 50% of SPs is surfactant associated proteins A (SPA), it is the most important part and plays an important role in physiological condition and many lung diseases.

• SPs中以肺表面活性物质相关蛋白A(SPA)含量最多，最重要，占SPs的50%25，在肺表面活性物质发挥生理作用及多种肺部疾病中起着重要作用。