Transmission and Scanning Electron Microscopy of the Human Ceruminous Apocrine Gland. I. Secretory Glandular Cells

The secretory portion of the apocrine sweat gland of the human external auditory meatus which is also called the ceruminous gland was observed by transmission and scanning electron microscopy. The secretory glandular cells contain a well developed smooth endoplasmic reticulum and Golgi apparatus. Cisternae of rough endoplasmic reticulum are often closely applied to large round mitochondria. These large mitochondria have no relationship to the secretory granules. Near the concave surface of the Golgi lamellae several tubules can be found. In these golgi-associated tubules a dark substance may accumulate to form specific large dense granules. Many less dense droplets or vacuoles may appear in these dark prosecretory granules and become liberated from their surface. Vacuoles formed in this manner then migrate to the apical cell surface and often discharge their contents into the gland lumen by the mechanism of exocytosis. Also, some of these vacuoles may be released into the lumen by the pinching off of small protrusions of cytoplasm, that is, they are released by the so-called apocrine secretory mechanism. Acid phosphatase activity was demonstrated not only in the dark prosecretory granules but also in clear vacuoles situated at the apical end of the cell and in the gland lumen. Such a histochemical finding may indicate that the secretory substance of the apocrine sweat gland may contain hydrolytic enzymes derived from lysosomes, which are the prosecretory granules of this gland, and these enzymes may play a role in dissolution and break down of the material extruded into the lumen by apocrine secretion. Apocrine secretory process of various sizes were observed on the luminal surface with the scanning electron microscope.