z google translate:

Endothelium (lat. Endothelium) refers to the cells of the innermost wall layer of the lymphatic and blood vessels (tunica intima) that are directed towards the lumen of the vessel. Regardless of their different structure depending on the type of vessel, all vessels from the cardiovascular system are lined with a single-cell layer of endothelial cells.

The total weight of all endothelial cells of an average person is 1 kilogram, the number of endothelial cells in a human body is a good 10 trillion and the area that comes into contact with the blood is 4,000 to 7,000 m². [1] This alone shows the importance of the endothelial system for the whole organism.

The posterior epithelium of the cornea is also often referred to as the corneal endothelium.