QS Study

Mechanism of Action of Clotting Factor

Most of the clotting factors are inactive forms of the proteolytic enzyme when they are converted into active forms; their enzymatic actions cause cascading reactions cat the clotting process. Therefore the functions of clotting factors are to trigger the formation of a blood clot and stabilize it for as long as necessary.

Blood Clotting is one of three mechanisms that reduce the loss of blood from broken blood vessels. Consequences of Blood Clotting Problems:

  • If blood clots too quickly / easily then thrombosis may occur.
  • Conversely, if blood takes too long to clot hemorrhage may occur.
  • The hereditary disorder haemophilia is a condition in which certain coagulation factors are missing from the blood, as a result of which the blood cannot form clots.

List of Clotting Factors

Factor I: Fibrinogen, Source: Liver

Actions: When fibrinogen is converted into fibrin by thrombin, it forms long strands that compose the mesh network for clot formation.

Factor II: Prothrombin Source: Liver

Actions: Prothrombin is converted into thrombin which then activated fibrinogen into fibrin.

Factor III: Thromboplastin / Tissue factor

Action: Injury to the blood vessel

Factor IV: Calcium (Bone and absorption from food in the gastrointestinal tract)

Action: Works with many clotting factors for activation of the other clotting factors.

Factor V: Ac-globulin (Ac-G) (Liver and platelets)

Action: Works with Factor X to activate prothrombin.

Factor VII: Serum prothrombin conversion accelerator (SPCA)

Actions: Activates Factor X which works with other factors to convert prothrombin into thrombin.

Factor VIII: Anti-hemoplytic factor

Deficiency: Hemophilia A

Factor IX: Christmas factor (Deficiency: Hemophilia B)

Actions: Works with Factor VIII and calcium to activate Factor X.

Factor X: Stuart factor (Source: Liver)

Actions: Works with platelet phospholipids to convert prothrombin into thrombin. This reaction is made faster by activated Factor V.

Factor XI: Plasma thromboplastin antecedent (PTA) (Source: Liver)

Actions: Works with calcium to activate Factor IX. (Deficiency: Hemophilia C)

Factor XII: Hageman factor (Source: Liver)

Actions: Works with prekallikrein and kininogen to activate Factor XI. Also activates plasmin which degrades clots.