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Factor XII

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Definition

noun

A blood coagulation factor which when activated acts on factor XI (antihemophilic factor C) to activate it


Supplement

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.

Factor XII is a blood clotting factor produced from the liver and is involved in the intrinsic pathway of blood coagulation cascade. In humans, the gene (i.e. F12 gene) coding for factor XII is located on the fifth chromosome, particularly 5q33-qter.

Factor XII is activated into factor XIIa upon contact to polyphosphates secreted by activated platelets. Its function in blood coagulation is to act on factor XI (antihemophilic factor C). Factor XI, when activated by factor XII, activate clotting factor IX (Christmas factor).

Factor XIIa also acts on plasminogen to be converted into plasmin, which is involved in clot degradation.

Deficiency of factor XII results in prolonged clotting time. This disorder though is generally asymptomatic and often detected only during presurgical laboratory screening.


Synonym(s):

  • Hageman factor
  • (blood) clotting factor XII
  • (blood) coagulation factor XII

See also: