Do the endothelium have one -way valves?

No, the endothelium itself does not have one-way valves. The endothelium is a thin layer of cells that lines blood vessels and is involved in regulating vascular functions. One-way valves are typically found in veins, particularly in the limbs, to prevent backflow of blood. These valves work in conjunction with the muscular actions of the surrounding tissues to facilitate blood flow toward the heart.