Answer
The result of the first stage of clotting is the formation of prothrombinase. Prothrombinase converts prothrombin to thrombin (a liver enzyme) which catalyses the conversion of fibrinogen to fibrin.
Work Step by Step
In both the extrinsic pathway (triggered after tissue damage) and the intrinsic pathway ( triggered after damage of endothelial cells) the first stage of coagulation leads by several steps to the formation of thrombokinase .
In the second stage of coagulation (in the common pathway), thombokinase converts the plasma protein prothrombin (made in the liver) to the enzyme thrombin. In the third stage of coagulation (also in the common pathway) the enzyme thrombin catalyses the transformation iof fibrinogen into fibrin. Loose weak strands of fibrin at first tie up the RBCs, but soon the action of Factor XIII stenghtens the strands of fibrin and bind the RBCs into a firm clot.
