Abstract
Fine morphology of the corneal endothelium was examined by light microscopy, and scanning and transmission electron microscopy using chick embryos on day 5 to 18 of incubation. By light microscopy, the corneal endothelium from 5-day-old embryo was composed of asymmetrical cells of various size with a large number of cellular processes. From embryonic day 6 to day 8, it consisted of 1-2 layers of the cells, but the intercellular space was incomplete. On embryonic day 9, it became a single layered structure of uniform thickness, resembling the postnatal form in appearance. Microvilli were seen on the posterior surface from embryonic day 6 till day 12 under the scanning and transmission electron microscope. From embryonic day 7 henceforth, the cilium was visible in the center of each cell. The microvilli were uniform and had internal fibrous laminar structure, while the cilium had composite axial structure similar to those of the human embryonic corneal endothelium. Both the cilium and microvilli were found before the onset of excretion of the aqueous humor. The microvilli, in addition to absorption, are regarded to be responsible for increasing the surface area for intercellular metabolism. It is suggested that the cilium, which basically has motor function, eliminates the impurities from the anterior chamber before the onset of aqueous humor circulation, and later assists the aqueous humor circulation.
