Endothelium
Diagram showing the location of endothelial cells
Transmission electron micrograph of a microvessel showing endothelial cells, which encircle an erythrocyte (E), forming the innermost layer of the vessel, the tunica intima.
System	Circulatory system

Endothelium is a layer of cells that line the walls of the circulatory system which carries blood around the body. The cells form a membrane so that certain substances, such as nutrients, can move through the walls. In an adult human there is about 1 kg of endothelium cells, which would cover an area of about 7m². The endothelium plays an important part in controlling the flow of blood around the body. view more...