10 CORE PATHOLOGY
Blood circulatory system
unstructured and forms when blood clots outside the circulatory system.
The process of thrombus formation, termed thrombosis, is due to activation of the normal blood coagulation system. Aggregation of platelets, held together with a meshwork of fibrin, is a normal hemostatic mechanism, occurring constantly to plug small defects in blood vessel wall. The result is the formation
of a hemostatic plug composed of fibrin, platelets and entrapped red cells. The thrombus should be considered as a biologically active structure, rather than a passive physical plug. Peptide fragments derived from the coagulation cascade and factors released by platelets have effects on adjacent endothelium and the vessel wall, promoting repair. Once the defects is plugged effectively and the vessel wall repaired, the small platelet/fibrin thrombus is normally removed by fibrinolysis, a multi-enzyme process that breaks down the supporting mesh of fibrin filaments, allowing dissolution of the thrombus.