- The clotting factors are a group of chemicals in the blood which is responsible for the formation of blood clot.
- Clotting factors are usually inactive but once there is an injury to the wall of the blood vessel, they get activated.
- The function of clotting factors is to trigger the formation of a blood clot and stabilize it for as long as necessary.
- Clotting factors are therefore known as procoagulants.
MNEMONIC for Clotting Factors:
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Factor I – Fibrinogen; common pathway; converted to fibrin.
Factor II – Prothrombin; common pathway; converted to thrombin that converts fibrinogen to fibrin.
Factor III – Tissue factor (TF) or thromboplastin; extrinsic pathway.
Factor IV – Calcium ions (Ca2+); always present, needed for coagulation.
Factor V – Labile factor, Proaccelerin; common pathway.
Factor VI – not used
Factor VII – Stable factor, Proconvertin; both extrinsic & intrinsic pathway.
Factor VIII – Antihaemophilic factor (AHF); intrinsic pathway: deficiency leads to hemophilia A.
Factor IX – Christmas factor, Plasma thromboplastin component (PTC); intrinsic pathway; deficiency leads to hemophilia B.
Factor X – Stuart-Prower factor; common pathway.
Factor XI – Plasma thromboplastin antecedent (PTA); intrinsic pathway; deficiency leads to hemophilia C.
Factor XII – Hageman factor; intrinsic pathway; activates plasmin.
Factor XIII – Fibrin stabilizing factor (FSF); common pathway; cross-links fibrin.
Factor VIII & IX are sex-linked characters, others are autosomal.