ONTOGENY OF THE CUTANEOUS SENSORY ORGANS

The ontogeny of cutaneous sensory nerve organs is described in higher vertebrates, and includes the lamellated corpuscles of Meissner, Pacin i and Herbst, and the Merkel cell-neurite complex with bird Merkel and Grandry corpuscles, and mammalian Merkel cells. The main common featu re is that for most corpuscles there is an inside-out order of assembl y around the nerve ending which is present from the beginning of end-o rgan ontogeny. The exception is the mammalian Merkel cell which is pre sent in the epidermis before the entrance of nerve fibers, and could p lay a promotional role in the development of skin innervation. The dev elopmental origin of Herbst and Merkel corpuscles in birds is reported as demonstrated using embryological experiments with cell markers. Co nclusions are that inner bulb cells of Herbst corpuscles and bird Merk el cells are of neural crest origin, whereas other cells (inner space and capsular cells for Herbst corpuscle and capsular cells for Merkel corpuscles) are provided by the local mesenchyme. The question of the ontogeny of mammalian Merkel cells is discussed in relation to the two debated hypothesis of epidermal and neural crest origins. Morphogenet ic interactions during the development of cutaneous sensory end organs are also discussed. (C) 1996 Wiley-Liss, Inc.