How does blood clotting work?
A break in the blood vessel wall exposes proteins that attract platelets and initiate coagulation, the conversion of liquid components of blood to a solid clot. The coagulant, or sealant, circulates in an inactive form called fibrinogen. In response to a broken blood vessel, platelets release clotting factors that trigger reactions leading to the formation of thrombin, an enzyme that converts fibrinogen to fibrin. Thrombin also activates a factor that catalyzes the formation of more thrombin, driving clotting to completion through positive feedback.