Eventually the intrinsic pathway activates factor X, a process that can also be brought about by the extrinsic pathway. The precise role of factor VIII in this reaction is not clearly understood. Its presence in the complex is obviously essential, as evidenced by the serious consequences of factor VIII deficiency experienced by haemophiliacs. The extrinsic pathway is an alternative route for the activation of the clothing cascade. The main function of the extrinsic pathway is to augment the activity of the intrinsic pathway.
Tissue factor is present in most human cells bound to the cell membrane.
The activation process for tissue factor is not entirely clear. Clot formation . The end result of the clotting pathway is the production of thrombin for the conversion of fibrinogen to fibrin. Fibrinogen is a dimer soluble in plasma. Exposure of fibrinogen to thrombin results in rapid proteolysis of fibrinogen and the release of fibrinopeptide A .