Summary

Blood coagulation is an important mechanism that maintains theintegrity of the vascular system to prevent blood loss after injury. Theconceptions on the working mechanism of coagulation are based on thewaterfall or cascade model, which was already proposed more than30 years ago, independently by Davie and Ratnoff (1) and MacFarlane(2). Blood coagulation was viewed as a series of linked proteolytic reactionsin which zymogens are converted into serine proteases, ultimatelyleading to the formation of thrombin, which converts soluble fibrinogeninto insoluble fibrin. Coagulation was thought to proceed via twopathways, an extrinsic and an intrinsic pathway. Activation of the extrinsicpathway of coagulation occurs by the exposition of tissue factorat the site of injury (3) whereas the intrinsic system is activated after exposureof plasma to an activating surface. Although the in vivo activa-ingsurface is unknown, the contact system was believed to play a rolein the initiation of the intrinsic pathway....