ABSTRACT
The endothelium, which lines the blood vessels of the vascular tree, is a truly pervasive cell layer, weighing 1 kg in an average-sized human and covering a total surface area of 4000-7000 m2 (1). Endothelial cells from a single human, when lined end-to-end, would wrap more than four times around the circumference of the earth. The endothelium is not inert, but rather is highly active, participating in several physiological processes, including the control of vasomotor tone, the trafficking of cells and nutrients, the maintenance of blood fluidity, the regulation of permeability, and the formation of new blood vessels (2).
