Endothelium

General medical term referring to the lining cells on the inner surface of any living tissue. In relation to the cornea of the eye, this means the delicate cells on the inside surface. These cells serve a ‘pump function’ in that they pump fluid out of the cornea and into the aqueous humor. If the endothelial pump function is impaired, the cornea would swell and lose its’ optical clarity, turning instead a milky white.