Platelets function both mechanically and biochemically in the process of hemostasis. When injury to a blood vessel occurs, platelets aggregate, forming a primary hemostatic plug, which helps stop blood flow.
Platelets also release certain substances, among them serotonin. Serotonin causes the blood vessels in the area to constrict, thereby further stopping the flow of blood.
Platelets also can have a membrane-bound substance called Platelet Factor 3 (PF3). PF3 catalyzes the coagulation reaction, which results in the formation of a fibrin clot. Platelets also maintain the integrity (leak-free) state of blood vessels.
