Desquamation of the corneal epithelium in the immature mouse: a scanning and transmission microscopy study

Abstract

The normal immature mouse corneal epithelium as characterized by scanning electron microscopy (SEM) is composed of dark, medium and light cells covered with surface microvilli. Microvilli are more numerous on the light and medium than the dark cells. In transmission electron microscopy (TEM) light cells of SEM are electron dense. The medium and dark cells of SEM on the other hand, have pale cytoplasm with few microvilli. The process of epithelial desquamation in the above cell population was detailed sequentially. The initial step in desquamation of a surface cell is swelling and reduction in number of surface microvilli. This is followed by the appearance of dehiscences or slits in the plasma membrane of surface cells. In TEM these dehiscences are readily visible as small slits in the apical plasma membrane of cells with pale appearing cytoplasm. Next, the desquamating cell pulls away from its lateral cell borders. Finally, the cell detaches from the intermediate cell layer by rupture of desmosomes. This mechanism of desquamation would not appear to contribute to or to insure stability of the mucin component of the precorneal tear film.