Ultrastructures of the normal surface of corneal epithelium of the heterozygous rhino mouse with special reference to so-called epithelial holes.

The surface structures of the corneal epithelium of the heterozygous rhino mouse were examined by transmission electron microscopy and scanning electron microscopy. The surface structures of the corneal epithelium were composed of microvilli, microplicae and epithelial holes. Microvilli and microplicae showed the same features as those described previously. However, some microvilli bent at the top of stalk and looked like microplicae by scanning electron microscopy. The structure of epithelial holes was different from that reported previously. Epithelial holes with elevated rim demonstrated by scanning electron microscopy were formed by a large fold or process of epithelial cells in the outermost layer. Microvilli were present on the process (margin) and floor of epithelial holes. Thus microvilli on the floor belong to the outermost layer, not to the second layer.