The Online Encyclopedia and Dictionary







Hemostasis refers to a process whereby bleeding is halted in most animals with a closed circulatory system.

Hemostasis in Physiology

Hemostasis may refer to the physiologic process whereby bleeding is halted.

When a wound occurs in a blood vessel, several interconnected steps occur to staunch the flow of blood.

  • vasoconstriction constricts the blood vessel, minimizing vessel diameter and slowing bleeding.
  • primary hemostasis occurs, wherein platelets, one of the formed elements of the blood, bind to collagen in the exposed walls of the blood vessel to form a hemostatic plug within seconds after an injury.
  • secondary hemostasis or coagulation occurs. This is a complex cascade of coagulation factors ultimately resulting in the transformation of fibrinogen, a blood protein, into polymerized fibrin, making a clot. This process takes several minutes.
  • The clot attracts and stimulates the growth of fibroblasts and smooth muscle cells within the vessel wall, and begins the repair process which ultimately results in the dissolution of the clot (clot lysis).

Disorders of hemostasis can be roughly divided into platelet disorders, such as idiopathic thrombocytopenic purpura, and disorders of coagulation, such as hemophilia.

Hemostasis by Hemostatic Clamps

Hemostasis may refer to the process of manually clamping a blood vessel, usually with hemostatic clamps, in surgery or dissection, to prevent bleeding from that vessel.

Last updated: 06-01-2005 22:04:56
Last updated: 09-12-2005 02:39:13