Which coagulation pathway is activated by contact with a damaged vessel?

The intrinsic pathway is activated when blood comes into contact with damaged vascular surfaces, such as exposed collagen from the endothelium of a vessel. This pathway is part of the coagulation cascade that is initiated by factors that are intrinsic to the blood itself, such as factor XII, which is activated by contact with negatively charged surfaces. Once activated, the intrinsic pathway leads to a series of enzymatic reactions resulting in the activation of factor X, which is a critical step in the formation of a fibrin clot.

In contrast, the extrinsic pathway is primarily initiated by tissue factor (TF) released from damaged tissue when there is significant vascular injury; it typically responds faster than the intrinsic pathway. The common pathway refers to the final series of steps shared by both the intrinsic and extrinsic pathways, culminating in the conversion of prothrombin to thrombin. The fibrinolytic pathway, on the other hand, is involved in the breakdown of clots, rather than their formation.