Further Studies on the Ultrastructure of the Human Axillary Apocrine Sweat Glands

Abstract

Secretory cells of the human axillary apocrine sweat gland were studied with the transmission electron microscope. They contain several different kinds of granules. Small granules and vesicles about 150 nm in diameter are arranged immediately beneath the luminal surface membrane. These granules are extremely variable in electron density, from very dense granules to clear vesicles. Some of these vesicles are opened to the gland lumen, and are suggestive of exocytosis. Some balloon-like cytoplasmic projections contain these vesicles. Therefore, it seems that the apical granules and vesicles are secretory in nature, and are released into the lumen by either exocytosis or an apocrine mechanism. They are stained well with the methenamine silver method, and are probably formed in the Golgi apparatus. Large dense granules are accumulated in the supranuclear cytoplasm. They contain small dense particles and medium-sized vacuoles. It is not likely that apical secretory granules or vesicles are derived from these large dense granules or the vacuoles in them. Medium-sized cored vacuoles are probably the precursors of large dense granules. A complex of loosely aggregated granules and droplets is also observed, and is thought to belong to the true lysosomes. It is suggested that the Golgi apparatus or GERL may produce the apical secretory granules and cored vacuoles. Mitochondria may develop into large, less dense granules due to a strong accumulation of matrix substance. The significance of such enlargement of mitochondria cannot be known yet. Infoldings of basal plasma membrane are observed, and while some of them are true infoldings, most of them are intercellular interdigitations.