<prompt> Adhesion of platelet to collagen is due toFactor 9FibrinogenVon willebrand factorFibrionectin  <response>: Ref Robbins 9e p117 Von Willebrand Factors primary function is binding to other proteins, in paicular factor VIII, and it is impoant in platelet adhesion to wound sites. It is not an enzyme and, thus, has no catalytic activity. VWF binds to a number of cells and molecules. The most impoant ones are: Factor VIII is bound to VWF while inactive in circulation; factor VIII degrades rapidly when not bound to VWF. Factor VIII is released from VWF by the action of thrombin. In the absence of VWF, factor VIII has a half-life of 1-2 hours; when carried by intact VWF, factor VIII has a half-life of 8-12 hours. VWF binds to collagen, e.g., when collagen is exposed beneath endothelial cells due to damage occurring to the blood vessel. Endothelium also releases VWF which forms additional links between the platelets glycoprotein IbIXV and the collagen fibrils 