Cell types in cutaneous type I mechanoreceptors (Haarscheiben) and their alterations with injury

Abstract

Type I mechanoreceptors (also called Haarscheiben or “domes”) are small elevations on the cat's skin, each being supplied by a myelinated sensory fiber. The fiber terminates in apposition to specialized receptor cells (Merkel cells) lying at the base of the epithelium investing the structure. When a group of domes was injured some of the neighboring domes became structurally altered as determined by light and electron microscopy. The changes observed resembled those which accompany denervation and involved the loss of Merkel cells and their apposed sensory nerve terminals from the dome. Since this trauma was produced indirectly it has been called secondary injury. Cells showing some of the morphological features of both keratin-producing epithelial cells and Merkel cells were observed in secondarily injured domes and in non-injured domes. The presence of such transitional cells suggests that Merkel cells may be derived from keratinocytes.