Platelet activation and interactions with the microvasculature.

Platelet adherence to structurally or functionally damaged endothelium and its subsequent activation are multifaceted events. Regulation of the rate and extent of platelet adhesion is under local control by the platelets and endothelium. Even in the absence of platelet adhesion to endothelium or subendothelium, there is a complex hemostatic balance of coagulation and anticoagulation. This is mediated by the manufacture, release, and inactivation of various procoagulant and anticoagulant compounds, predominantly by the platelets and endothelium. The relationship between the two in maintaining the homeostasis of coagulation and other processes is complex. This review focuses on the structure, function, and interaction of endothelium, subendothelium, and platelets and on their vasoactive and pro-/anticoagulant functions.