Electron Microscope Studies of the Human Epidermis The Cell Boundaries and Topography of the Stratum Malpighii*

The thin skin of the left upper quadrant of the human abdomen has been studied by electron microscopy. Tissue removed with a high speed rotary punch was fixed in osmium tetroxide or potassium permanganate. The latter fixative in our preparations is superior to osmium for the demonstration of epidermal cell membranes and certain other membranous structures of the epidermis. The cytoplasmic membranes of basal cells and cells of the stratum granulosum have been found to be relatively straight, while those of most spinous cells are sharply scalloped. The deep cells of the stratum spinosum in the rete ridge area show cell membranes and cytoplasmic structure intermediate between true basal cells and most cells of the stratum spinosum. The extracellular material of the desmosome has been found to consist of alternate dark and light laminae similar to those described by Odland (13) and Horstmann and Knoop (7). Many aspects of the structure of the epidermis have been clarified by recent electron microscope studies. A basement membrane has been clearly shown by Weiss and Ferris (21) and Selby (17). The coarse tonofibrils seen in light microscopic preparation have been shown to be composed of bundles of submicroscopic filaments (tonofilaments) by Porter (15, 16), Selby (17, 18), Charles and Smiddy (3), and Menefee (11). A dendritic cell, quite different structurally from the ordinary epidermal cell, has been described by Odland (13) and Clark and Hibbs (4). The structural characteristics of this cell indicate that it is the epidermal melanocyte and it has been shown to be "dopapositive" in electron micrographs (5). Such cells were first demonstrated in electron micrographs by Birbeck, Mercer, and Barnicot (2) and Barnicot, Birbeck, and Cuckow (1) in studies of the hair bulb. Electron micrographs have been quite valuable * Supported by grants from the United States Public Health Service, H 2490 and A 1150. ~; Markle Scholar in Medical Science.