part of part of blood coagulation protein activation cascade blood coagulation, fibrin clot formation See also the biological process term 'blood coagulation, intrinsic pathway ; GO:0007597'. GO:0072378 2010-11-22T03:09:32Z A protein activation cascade that contributes to blood coagulation and consists of the cascade of enzymatic reactions initiated by physical damage to the wall of a blood vessel, leading to the formation of a formation of a fibrin clot at the site of the injury. The process also includes numerous positive and negative regulatory events.