VON WILLEBRAND FACTOR 
SUBENDOTHELIUM 
Schematic illustration of the biosynthesis and function of von Willebrand factor. Red ovals repre- 
sent the factor, which is synthesized in the bone marrow megakaryocyte (precursor of blood 
platelets) and in the vascular endothelial cell. It is assembled through several steps into a large 
complex containing up to 100 subunits. Bound to von Willebrand factor, in the circulating 
blood, is the antihemophilic factor VIII (blue triangle). In addition to carrying factor VIII, von 
Willebrand factor serves as a major adhesive link between platelets and the blood vessel wall at 
sites of injury. 
Research of David Ginsburg. 
162 
