Factor VIIa (Last Updated - 2/27/2005)

-makes up a step of the extrinsic pathway
-formed via activation of Factor VII --> the efficacy of this reaction is increased by tissue factor (TF)
-Catalyzes the activation of 2 very important Factors of the clotting cascade:
     1) Along with tissue factor & Factor XIa:
          -catalyzes the activation of Factor IX to IXa --> crossover point b/w the extrinsic and intrinsic pathways
     2) Along with calcium (Factor IV), phospholipids, Factors VIIIa & IXa:
          -catalyzes the activation of Factor X to Xa --> crossover point b/w the common pathway and the extrinsic 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.