Figure 1.

The role of von Willebrand factor (VWF) in hemostasis. After vessel injury, subendothelium becomes exposed with collagen and VWF contained in the subendothelial matrix. The interaction of von Willebrand factor with glycoprotein Ibα (GpIbα), naturally exposed on the platelet surface, creates initial adhesion of platelets to the subendothelium and platelet activation. This makes the platelets to expose glycoprotein IIb/IIIa (αIIbβ3) which binds fibrinogen and VWF thus, increasing platelet plug. Factor VIII is bound to VWF and is naturally conveyed to the site of lesion, thus allowing also the generation of adequate amounts of fibrin (modified by courtesy of AB Federici).