The human external auditory canal secretory system — an ultrastructural study

Human external auditory canal skin, with a special emphasis on the secretory system, was studied by light, transmission electron and scanning electron microscopy. Two types of secretory glands were observed: modified apocrine (ceruminous) and sebaceous. The sebaceous secretory cells showed a typical holocrine mode of secretion, and its secretory vacuoles were homogeneous; on the other hand, modified apocrine secretory cells contained heterogeneous secretory granules. They were ither dark granules or light granules. In addition to these granules there were secretory vesicles. Evidence to support both the apocrine as well as the eccrine mode of secretion was noted in the modified apocrine gland. This finding is partly in agreement with early reports based on light microscopy which suggested only an apocrine mode and data based on transmission electron microscopy which showed only the eccrine mode. Significance of the secretion by the external ear canal and its role in a local immune defense system is discussed.