Tissue Factor (TF) (Last Updated - 2/27/2005)

-aka. Factor III
-present on all cells not in contact w/ plasma (Ex.) smooth muscle cells & fibroblasts) --> extrinsic to plasma
-initiates coagulation (via extrinsic pathway) via increased efficiency of Factor VIIa
-also along with Factors VIIa & XIa catalyzes the activation of Factor IX to IXa
-b/c tissue factor & Factor VIIa are from the extrinsic pathway and they both can participate in the activation of Factor IX to IXa (along with Factor XIa) --> this is the crossover point b/w the extrinsic to the intrinsic pathway

-click here to view an image of the clotting cascade

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References:

Goodman & Gilman's: The Pharmacologic Basis Of Therapeutics - 10th Edition - 2001. Chapter 55.