Blood clotting intrinsic mechanism

A blood clot is formed mainly from a network of crosslinked fibrin molecules that traps platelets, erythrocytes, and other materials to form a solid clot. The aggregation and cross-linking of fibrin is the final stage of a proteolytic cascade or pathway which is triggered by one or both of two mechanisms the intrinsic pathway and the extrinsic pathway. 

Figure 2. Proposed mechanism for blood clotting in mammalian plasma in the intrinsic system. The factor on the left side of reaction (zymogen) is converted to active enzyme by proteolysis. PL = phospholipids. (16a)...

The intrinsic pathway is involved in the clotting of blood in glass tubes and in the undesirable intravascular clotting that results in thrombosis. Control of the clotting mechanism is thus central to hemostasis to avoid bothhemorrhage and thrombosis. 

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