Write long note on extrinsic pathways of blood clotting.

Extrinsic pathway of blood clotting:
It triggers the initiation phase of blood coagulation and is required for thrombosis which is clotting of blood inside the blood vessels. The extrinsic pathway contains transmembrane receptor tissue factor and plasma factor VII and VIIa. This pathway is triggered due to external trauma and is quicker than the intrinsic pathway which is triggered due to internal trauma. It eventually leads to the formation of prothrombin activator or factor X which converts prothrombin to thrombin. This thrombin when produced in sufficient amount cause fibrinogen to convert to fibrin and form a clot.

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