Final answer:
In the common pathway of coagulation, factor Xa combines with factor Va and calcium ions to form prothrombin activator, leading to the conversion of prothrombin to thrombin, which is essential for blood clot formation.
Step-by-step explanation:
In the common pathway of coagulation, factor Xa combines with factor Va and calcium ions to form the prothrombin activator. This enzyme complex is crucial in converting prothrombin (factor II) to thrombin, an active enzyme that plays a pivotal role in the clotting process. Thrombin then acts to convert fibrinogen to fibrin, creating the meshwork that forms the basis of a blood clot.
Factor X, also known as the Stuart-Prower factor, can be activated by both the intrinsic and the extrinsic pathways of blood coagulation. In the extrinsic pathway, factor VII, in the presence of calcium ions and tissue factor (factor III), fast-tracks the activation of factor X. Whereas in the intrinsic pathway, factor VIII and factor IX form a complex to activate factor X. Subsequently, activated factor X (factor Xa), along with factor Va and calcium ions (factor IV), form the prothrombinase complex, which is essential for the conversion of prothrombin to thrombin in the final common pathway of blood coagulation.