Definition of endothelium
noun(plural endothelia /-lēə/)
- the tissue that forms a single layer of cells lining various organs and cavities of the body, especially the blood vessels, heart, and lymphatic vessels. It is formed from the embryonic mesoderm. Compare with epithelium.
late 19th century: modern Latin, from endo- 'within' + Greek thēlē 'nipple'