Electron microscopic study on the duct of the human eccrine sweat gland with special remarks on the transitional portion epithelium.

Long tubular excretory duct of the human eccrine sweat gland has been divided by light microscopy into three portions: the initial or coiled portion which is included in the glandular coil, the ascending or straight portion which runs in the dermis toward the epidermis and the terminal or intraepidermal portion which ascends spirally through the epidermis toward the free surface of the skin to empty there. ITO and ENJO (1949) and ITO, ENJO and UCHIDA (1954) have cytologically observed these three portions with the light microscope demonstrating in epithelial cells the Golgi apparatus, mitochondria, centriole, glycogen as well as the intercellular bridges between them; they designated the so-called cuticular border of the epithelium encircling the lumen especially as "crusta". In the just mentioned light microscopic study, ITO and ENJO have discovered in the human sweat gland coil the existence of a short "transitional portion" between the secretory portion and the coiled portion of the duct in which the epithelium lining the lumen shows a transitional character between the epithelia of the both portions. The electron microscopic studies on the human eccrine sweat duct have been carried out by HIBBS (1958), CHARLES (1960) and MUNGER (1961) and on the animal eccrine duct by MUNGER and BRUSILOW (1961, cat), ELLIS and MONTAGNA (1961, monkey) and MATSUZAWA and KUROSUMI (1961, rat). But the transitional portion has been observed only by HIBBS (1958). In the present mainly electron microscopic and partially light microscopic study the epithelium of the coiled portion of the human eccrine sweat duct and the transitional portion will be described.