Question

Sort the following clotting factors from top to bottom starting from the factor coming after thromboplastin:

• A. Fibrinogen
• B. Fibrin
• C. Thrombin
• D. Prothrombin

Answer 1

When the blood vessels are damaged, they attract platelets, which form the platelet plug. But the platelet plug is not very strong and needs to be stabilised. This is done with the help of fibrin. The damaged endothelial cells express tissue factor. The tissue factor initiates a coagulation cascade. The end result of the cascade is the formation of an enzyme called prothrombinase. This prothrombinase cleaves prothrombin giving rise to thrombin. The platelets have specific thrombin receptors. The thrombin binds to the receptors on the platelets in the platelet plug. Thrombin acts on fibrinogen in the plasma and cleaves it to form insoluble fibrin strands.The insoluble fibrin strands are then stabilized to form a clot by fibrin stabilizing factor which is also activated by thrombin.