coagulatiecascade

The coagulation cascade, also known as the blood clotting cascade, is a complex series of biochemical reactions that ultimately leads to the formation of a blood clot. This process is essential for hemostasis, which is the cessation of bleeding from a damaged blood vessel. The cascade involves a series of inactive enzymes called zymogens, which are sequentially activated by proteolysis, a process where one enzyme cleaves and activates another.

There are two main pathways that initiate the coagulation cascade: the intrinsic pathway and the extrinsic pathway. The intrinsic pathway is activated by damage to the blood vessel wall itself, exposing components that trigger the cascade internally. The extrinsic pathway is activated by tissue factor, a protein released from damaged tissues outside the blood vessel. Both pathways converge at a common pathway, which involves the activation of Factor X.

Activated Factor X then initiates the conversion of prothrombin to thrombin. Thrombin is a crucial enzyme in the cascade. It converts soluble fibrinogen, a protein present in plasma, into insoluble fibrin strands. These fibrin strands then form a mesh-like network that traps blood cells and platelets, forming a stable clot. The coagulation cascade is a highly regulated process, with both activators and inhibitors to prevent excessive clotting, which can lead to thrombosis.