FINE-STRUCTURAL AND MORPHOMETRIC STUDIES OF THE MERKEL CELL DURING FETAL AND POSTNATAL-DEVELOPMENT

[摘要] The morphological and morphometric changes of the Merkel cells during fetal and postnatal development were studied in the glabrous digital pads of rats. In 20-day-old fetal rats, the Merkel cells were present in the lower spinous and basal layers and not associated with axon terminals. The Merkel cell granules were few and sparse. The Merkel cell had clumps of fibrils and formed many desmosomes with surrounding keratinocytes. In postnatal rats, innervation was followed by an increase in the number of Merkel cell granules, and their specific accumulation. The fibrils of the Merkel cells were not prominent. The t test showed that the numerical density of the Merkel cell granules significantly increased from fetus to 4-day-old postnatal rats. Merkel cells may be present in the epidermis without nerve contact in 20-day-old fetal rats, and innervation is necessary for the increase of cellular activity in Merkel cells.