By activation of the intrinsic or extrinsic pathways or both, the common pathway is the continuation of the clotting process. The activation of factor X is the point where the two pathways converge to form the common pathway. The outcome of this process is the conversion of circulating insoluble coagulation factors into a gelatinous fibrin clot with entrapped blood cells, a blood clot.
Once Xa is formed, another cofactor, V, in the presence of calcium and latent factor 3 (PF3), converts prothrombin (factor II) to the active enzyme, thrombin (factor IIa). The activation of thrombin is slow, but once generated, it amplifies the clotting process. Thrombin acts to convert fibrinogen to fibrin. Thrombin activates factor XIII, resulting in the formation of a stronger, more durable fibrin clot.
