静脉瓣膜的结构与力学关系初探

THE RELATIONSHIP BETWEEN STRUCTURE AND MECHANICS OF THE VENOUS VALVE

The human venous valve of the brachial,femoral and long saphenous veins were examined with light,transmission and scanning electron microscopy.The observation shows that the venous valve is composed of three functional layers covered with endothelium on both surfaces.A loosely structured layer is located underlying the endothelium.A network mainly containing randomly oriented elastic fibers was found near the side towards the lumen.To the side towards the venous wall,there is a dense layer composed of eircumferentially and transversly oriented collagen bundles. Some smooth muscle cells extend from the wall of the vein to the base of the venous valve.The elastic fibers and smooth muscle cells together with the collagen fibers contribute to the mechanical load-bearing performance of the valve and to the passive closing and openning mechanism.In addition,the smooth muscle cells might play an active role in the normal functioning of the valve. The scanning and transmission electron microscopy of venous valve show different arrangement of the endothelium.On the surface of the valve next to the wall of the vein,the endothelial cells are transversely arranged,while on the other surface over which the current of blood flows,the cells are longitudinally arranged in the direction of the current.These accord with the role of fluid mechanics. 12 normal venous valves were tested by universal testing instrument (Instron type 1122).The mean value of the maximum tension of the valve is 1 N.The average value of the tensile ultimate strength is 10N/mm~2.