The extrinsic pathway is initiated by the release of factor III from damaged tissue to complex with factor VII and V.

The formation of a platelet plug is inhibited by healthy endothelium through the release of ADP.

Prothrombin is the enzyme that catalyses the conversion of fibrinogen into long fibrin fibres.

The intrinsic pathway is initiated by the activation of factor X.

Thromboxane A₂ is released by damaged vessel walls to initiate vasoconstriction.