Sequence of events in thrombogenesis. A, Major factors in pathophysiology of thrombus formation. B, Endothelial injury exposes subendothelium, initiating adherence of platelets and activation of coagulation system. C, Following platelet release reaction, ADP is released which causes further aggregation of platelets. D, Activated coagulation system forms fibrin strands in which are entangled some leucocytes and red cells and a tight meshwork is formed called thrombus.