Blutgerinnungskaskade

The Blutgerinnungskaskade, or coagulation cascade in English, is a complex series of biochemical reactions that leads to the formation of a blood clot. This process is essential for hemostasis, the cessation of bleeding, and is a critical defense mechanism against excessive blood loss following injury. The cascade involves numerous proteins called clotting factors, which are mostly enzymes that activate each other in a specific sequence.

There are two main pathways that initiate the coagulation cascade: the intrinsic pathway and the extrinsic pathway. The intrinsic pathway is activated by factors within the blood itself, such as contact with damaged endothelium. The extrinsic pathway is initiated by tissue factor, a protein released from damaged tissues outside the bloodstream. Both pathways converge on a common pathway, where thrombin is generated.

Thrombin plays a central role in the cascade. It converts soluble fibrinogen into insoluble fibrin. Fibrin strands then polymerize to form a meshwork that traps blood cells, creating the stable blood clot. This intricate cascade ensures that clotting occurs precisely at the site of injury while preventing widespread clotting throughout the circulatory system. Defects in the coagulation cascade can lead to bleeding disorders like hemophilia or thrombotic disorders, where clots form inappropriately.