A cytologic study of Grandry corpuscle development in chicken toe skin.

The developmental sequence of Grandry corpuscles was traced in the toe skin of embryonic, young and adult chickens by light and electron microscopy. The developing Grandry cells as well as Schwann cells can first be identified at stage 38 (approximately 12 days of incubation) due to the cytoplasmic content of scattered secretory granules of approximately 100 nm in diameter. Such developing Grandry cells are always associated with nerve fibers. During late stages (stages 40-42, 14-16 days of incubation) several immature Grandry cells formed cell clusters in the dermis. Such cell clusters were always in contact with growing nerve tips of Schwann cells. Immature Grandry cells were separated from one another and dispersed in the connective tissue compartment at stages 44-45 (near hatching). By the time of hatching the developing Grandry cells began to have the morphological characteristics of adult cells. They were relatively large in cell diameter (approximately 10 micron) containing numerous secretory granules and bundles of filamentous material. These cells had finger-like cytoplasmic processes. The Grandry cells at this time had an intimate relationship with nerve fibers and satellite cells. The fact that Grandry cells were always associated with nerve fibers throughout development would support the hypothesis that Grandry cells are derived from neural elements, perhaps neural crest. Satellite cells of Grandry corpuscles are apparently derived from Schwann cells. Grandry cells and corpuscles are adult in form by two to three months of age.