A Study on Embryonic Differentiation of the Keratinocyte : 2nd report : Ultrastructural and Quantitative Analysis of Mural Embryonic Epidermis

Ultrastructural investigations were carried out on the development of keratinocytes of mural embryos and fetuses from 9 to 20 days in utero, and using electron micrographs obtained by the study, changes of areas of cells and nuclei and of nucleo-cellular ratios of the basal and intermediate cells in the epidermis were quantitatively analysed with image analyser computer system (Luzex-500). It was revealed ultrastructurally that tonofibrils firstly appeared in the cytoplasm of the basal and intermediate cells at 15 days in utero, granular cells at 16 days and horny layer at 20 days with the regression of periderm, and revealed quantitatively that areas of nuclei as well as cells of both basal and intermediate cells parallelly showed the first peak at 11 days in utero, the lowest value at 15 days, and the second peak at 19 days. From the above, it was suggested that quantitative changes seen from 11 to 15 days in utero may be intimately related with the development of tonofibrils in the cytoplasm and of granular cells, and the changes at 19 days with the changes of the periderm into the horny layer and with the maturation of horny layer.