Dictionary > Prothrombin


A blood clotting factor that when activated converts into thrombin (factor IIa), which in turn activates factors I, V, VII, VIII, XI, XIII, protein C, and platelets
Coagulation, the process of clot formation, involves platelet and blood clotting factors. In humans, the coagulation mechanism is comprised of two processes, i.e. the primary hemostasis and the secondary hemostasis. The latter entails two pathways: (1) intrinsic pathway (contact activation pathway) and (2) extrinsic pathway (tissue factor pathway). Both pathways lead to the formation of fibrin.
Prothrombin is a blood clotting factor that is produced from the liver and is involved in both extrinsic and extrinsic pathways of blood coagulation system. It circulates in the blood plasma as an inactive glycoprotein. In the presence of thromboplastin and calcium, it converts into thrombin (its activated form). Thrombin is produced from prothrombin by the action either of the extrinsic system (tissue factor phospholipid) or, more importantly, the intrinsic system (contact of blood with a foreign surface or connective tissue). Thrombin acts on fibrinogen to produce fibrin.

  • thrombogen
  • (blood) coagulation factor II
  • (blood) clotting factor II
  • factor II

See also:

  • clotting factor
  • coagulation
  • thrombin
  • Related term(s):

    • Prothrombin time
    • Prothrombin test

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