Clotting Cascade Overview

Clotting Cascade

• The intrinsic pathway begins with vessel damage, exposing collagen, initiating a cascade of reactions.

• The extrinsic pathway begins with subendothelial cells or tissue damage, activating a separate cascade.

• Exposed collagen triggers factor XII activation.

• Factor XIIa activates factor XI, which then activates factor IX.

• Factor IXa, with its cofactor, activates factor X.

• Factor Xa, with its cofactor, converts prothrombin to thrombin.

• Thrombin converts fibrinogen to fibrin, forming a clot.

• Platelets are activated by thrombin and exposed collagen, contributing to clot formation.

• The extrinsic pathway involves tissue factor (factor III), which activates factor VII.

• Factor VIIa activates factor X, leading to thrombin formation and clot formation, similarly to the intrinsic pathway.

• The liver produces clotting factors, requiring vitamin K.

• Cofactors (e.g., phospholipid) enhance the efficiency of the clotting factors.

• A positive feedback loop amplifies the clotting cascade.