Hemostasis: The Body's Blood Clotting Process Explained

Hemostasis is the physiological process that stops bleeding from a damaged blood vessel. It occurs in three coordinated stages:

1. Vasoconstriction – Immediate narrowing of the injured vessel to reduce blood flow.
2. Primary hemostasis (platelet plug formation) – Platelets adhere to the exposed collagen, activate, and aggregate to form a temporary plug.
3. Secondary hemostasis (coagulation cascade) – A series of enzymatic reactions that generate fibrin, reinforcing the platelet plug into a stable clot.

Once the vessel wall is repaired, fibrinolysis dissolves the clot to restore normal blood flow. Disorders of hemostasis can lead to excessive bleeding (hemophilia, von Willebrand disease) or pathological clotting (thrombosis, disseminated intravascular coagulation).