A glycoprotein synthesized primarily in the liver and circulating in blood complexed with Von Willebrand Factor. FVIII participates in the intrinsic pathway of coagulation. It functions as a cofactor by accelerating the conversion of FX to FXa in the presence of FIXa, phospholipid, and calcium (tenase complex). FVIII must undergo limited proteoysis by Thrombin in order to demonstrate cofactor activity (FVIIIa). The gene for FVIII is X-linked and mutations in the gene give rise to a bleeding disorder, Hemophilia A. The slide show entitled Coagulation Pathways (All Components) shows how FVIII relates to the other coagulation factors. See also the slide show entitled Intrinsic Pathway-APTT.
