Mathematical Models for Blood Coagulation - Fluid-Structure Interaction and Biomedical Applications - page 504

Fig. 7.9 Scheme of the 3-pathway cascade model. Extrinsic pathway is also called TF-pathway.
An alternative name for the intrinsic pathway is contact activation pathway

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FXII FXIIa

FXI FXIa

Ca ++

FIX FIXa

Ca ++

FVIII FVIIIa

Ca ++

FX FXa

FV FVa

FII FIIa

FI FIa

Fig. 7.10 Sketch of the waterfall model of Davie and Ratnoff

(it includes the question mark concerning the activation of FXII) (Fig. 7.10 ). From
the appearance of FIXa onward the sequence in the sketch above is rather different
from the one we know (in which FVIII is activated by thrombin, FXa is a product of
the tenase complex, and thrombin is generated by prothrombinase) and in this form
it is autonomous from the extrinsic pathway.
The sketch of Fig. 7.9 has instead the correct chemical correlations, letting
products from extrinsic pathway (thrombin, FXa) enter the intrinsic pathway, which
becomes so to speak subsidiary. The purely intrinsicI pathway is instead based on
the assumption that FVIII is directly activated by FIXa (as in the original scheme),
which makes it really independent of the parallel extrinsic pathway.