Intrinsic System
The slow pathway of blood clotting.
In the complicated, biologically controllable intrinsic system, the rough surface of injured vascular structures first activates the contact labile Factor XII, which acts on the next stage of the system. From here, a cascade-shaped (coagulation cascade or waterfall mechanism; see figure) activation process begins, which leads via Factor XI and Factor IX to the activation of Factor X. For the reaction of the latter stage, Ca2+, factor VIII-complex and phospholipide from the platelets are additionally used as co-factors. (platelet factor 3, TF 3) is required. At the stage of joint activation of factor X by the intravascular and extravascular systems, the two reaction pathways merge.
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Coagulation Cascade (Waterfall Mechanism)