MRCP UK EXAMINATIONS

Detailed explanation-1: -Fibrinogen from alpha granules acts as a link between GPIIb/IIIa receptors on different platelets. Once platelets have linked together, a temporary platelet plug has formed, which is later fortified by the coagulation cascade of secondary hemostasis.

Detailed explanation-2: -Prostacyclin inhibits platelet aggregation and produces vasodilation whereas thromboxane A2 and endoperoxides promote platelet aggregation and cause vasoconstriction. The balance between the prostacyclin and thromboxane A2 determines the degree of platelet plug formation.

Detailed explanation-3: -Thus, aspirin inhibits platelet aggregation by irreversibly inactivating cyclo-oxygenase, a key enzyme in platelet prostaglandin metabolism, while the other nonsteroidal anti-inflammatory drugs and sulphinpyrazone cause reversible and dose-dependent inhibition of the same enzyme.

Detailed explanation-4: -von Willebrand Factor: The factor responsible for causing platelet adherence and aggregation. It is increased by positive feedback during platelet activation.