ABSTRACT

The integrity of the circulation is maintained through the provision of a rapid, potent, but tightly localized coagulation response to vascular damage. There is, however, one extraordinary problem in the regulation of hemostasis-blood flows. Normal hemostasis is the ability of the hemostatic system to control activation of clot formation and clot lysis to prevent hemorrhage without causing thrombosis. It classically involves vasoconstriction, platelet adhesion, and aggregation at the site of injury, leading to a plug formation. This is followed by fibrin formation consolidating the plug and rendering it stable. All of this occurs without clotting occurring elsewhere. Procoagulant products, whether clotting factors or platelets, must therefore be spatially localized to the site of damage for activation, and/or kinetically controlled so that they are inactive when distant from the damaged vessel.