SCANNING ELECTRON-MICROSCOPY OF THE BASAL SURFACE OF THE EPIDERMIS OFHUMAN DIGITS

The epidermal-dermal junction of the volar skin of human digits was ex amined by scanning electron microscopy (SEM). Fixed specimens obtained from cadavers were treated with 6 N NaOH to exfoliate the epithelium. The three-dimensional features of the basal surfaces were clearly vis ualized by SEM. Epithelial prolongations (intermediate and limiting ri dges) protruded towards the dermis, and transverse ridges were visible between them. Nerve fibers and Schwann cells were aggregated around t he sweat ducts on the intermediate ridges. Discoid structures were vis ible among the nerve fibers and Schwann cells. Examination by transmis sion electron microscopy of ultrathin sections of re-embedded specimen s confirmed that the discoid structures were nerve endings that covere d the Merkel cells. Minute projections were studded on the basal surfa ces of basal keratinocytes. The projections in the intermediate ridges appeared to be villous, whereas the profiles of those in the limiting ridges resembled cobblestones. This morphological difference might be a reflection of function.