Definition of Clotting Factors

Clotting-CascadeProteins in the blood that are essential for coagulation. Clotting factors circulate in the blood as inert proteins until the coagulation cascade initiates their conversion into participants in blood clotting.

Clotting factors interact with each other as well as other enzymes in the blood, notably fibrin and thrombin, to form blood clots.

Deficiencies of specific clotting factors cause coagulation disorders such as hemophilia (excessive bleeding) and thrombophilia (excessive clot formation). The liver produces clotting factors I (fibrinogen), II (prothrombin), V (proaccelerin), VII (cothromboplastin), IX (PLASMA thromboplastin), and X (Stuart-Prower factor).

Clotting Factors List and Names

Clotting FactorCommon NameFunction
antithrombinantithrombin III, antithrombin III,
coagulation inhibitor, AT-III
regulates thrombin, factor IX, factor X, factor XI, and factor XII to inhibit the coagulation cascade
factor Ifibrinogenforms fibrin clot after activation by thrombin in the final common pathway
factor IIprothrombintogether with factor Xa prothrombinase converts prothrombin into active thrombin, which in turn helps platelet aggregation
factor IIItissue factorinitiates extrinsic coagulation cascade following vascular injury
cofactor with factors VII, VIII, and IX in activating factor X
cofactor in activation of factor VII
factor IVcalciumrequired at several points in the coagulation cascade
factor Vproaccelerin or accelerator globulinnecessary to stop coagulation cascade at the end
factor VIaccelerin, factor Vaactivated form of factor V
together with factor X converts prothrombin to thrombin in the final common pathway
factor VIIserum prothrombin conversion accelerator (SPCA) or cothromboplastinactivates factor X when calcium and factor III (tissue factor) are present
factor VIIIantihemophilic factor Aactivates platelet aggregation and adhesion cofactor with factor IX in activating factor X
factor IXChristmas factor, antihemophilic factor B, or plasma thromboplastin component (PTC)cofactor with factor VIII in activating factor X (vitamin K-dependent)
factor XStuart factor or Stuart-Prower factoractivated by complex of tenase (factors VII and IX), factor VII, and calcium to enable platelet aggregation
Initiates conversion of factor II (prothrombin) to thrombin
factor XIplasma thromboplastin antecedent (PTA)in the intrinsic pathway, activates factor IX when calcium is present
factor XIIHageman factoractivates factor XI, thereby starting the intrinsic pathway
binds to exposed collagen at site of intravascular injury
factor XIIIfibrin stabilizing factor (FSF), fibrinoligase, fibrinase, plasma transglutaminase, Laki-Lorand factor, LL factor, LLF, or protransglutaminasecross-links and stabilizes fibrin clot after activation by thrombin
needs calcium as cofactor
high molecular weight kininogen (HMWK)contact activation factor, Fitzgerald factor, Flaujeac factor, Williams-Fitzgerald-Flaujeac factor, or Williams factoractivates factor XII early in the intrinsic pathway
prekallikreinFletcher factor or prokallikreinactivates factor XII at very beginning of the intrinsic pathway
protein Canticoagulant protein Climits functions of factor V and factor VIII
with cofactor protein S, inhibits thrombin to block fibrin clot formation
protein Santicoagulant cofactor protein Slimits functions of factor V and factor VIII
as cofactor for protein C, inhibits thrombin to block fibrin clot formation
thrombomodulinfetomodulincell surface receptor that binds excess thrombin, thus inhibiting dangerous clot formation


Clotting Factors – Definition, Names and List
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