Surface pattern differentiation of the epithelial cells of the human uterine ectocervix

This review considers the SEM cell surface pattern of the human ectocervical stratified squamous epithelium and its differentiation during migration from the basal to the exfoliating layer. The outer surface of flattened superficial cells has been generally characterized by microridges. Although this surface pattern is indeed relatively stable -as follows from an apparently limited sensitivity to preparation factors- it also shows dependency on the hormonal state of the patient. In contrast to the superficial cells very little information is available on the surface structure of the normal intermediate, parabasal and basal cells. The deep surfaces of the superficial cell layers have been examined using a stripping technique, whereas the surfaces of the deeper cell layers have been investigated with a freeze-fracturing technique. During migration from the basal cell layer upwards, the following structural parameters change gradually: the shape of the cells, the size of the intercellular space and the length and width of the cellular processes. As a result of the differentiation process the flattened cells of the superficial zone acquire microridges and crests on the luminal side. These interdigitate respectively, with globular microvilli and furrows present on the basal side of the overlying cell. Crests and furrows delineate regions on the cell surface in which variable microridge- and microvillus-patterns appear. Because crests and furrows are not present on the cell margins but also more centrally on the surface, the cell surface shown "regional" differences. The functional significance of the cell surface structure is discussed. Whereas the surface processes of the basal and parabasal cells presumably are engaged in the enhancement of intercellular contact and must permit metabolic interchange with the intercellular space, the interdigitating processes of superficial cells probably deal with an increase of the surface adhesiveness and in particular the resistance to sideways movements.