抄録
Cell biological characteristics of the outer root sheath (ORS) of normal human hair follicle have been reviewed. In anagen hair follicle, two cell layers of the ORS are present at the outermost part of hair bulb. The inner one moves up and forms the innermost cell layer of the ORS as a single cell layer, which keratinizes at follicular isthmus after production of keratohyaline granules (KG). While, the outer one suddenly increases its cell number at the suprabulbar level and, above the level of keratogenous zone of hair cortex, these outer cells have clear cytoplasm containing glycogen. At the isthmus, they become longitudinally flattened in cell shape losing glycogen and keratinze toward hair canal without KG production, but with production of many lamellar granules. The basal lamina around the ORS gradually becomes thick up to 1 or 2μm in anagen and degenerated probably by collagenases secreted from retracting ORS in catagen. The ORS cells surrounding the club hair root are not rich in glycogen and show KG-absent keratinization. Stainings of BrdU, involucrin, desmosomes, keratins and lectins for the ORS have been introduced. In conclusion, the cell biological characteristics of trichilemmal tumors are similar in some points to, but different in many points from those of the normal ORS.
