Hayward A F, Kent A P
Cell Tissue Res. 1982;227(3):619-31. doi: 10.1007/BF00204792.
The sequence of events in the establishment of a keratinised epidermis has been related to age and crown rump length in fetal rats. Differentiation of the epidermis occurs under cover of the periderm throughout gestation. Ten stages are defined between 12d intra-uterine life and birth. Membrane-coating granules (MCGs) appeared at 18d (Stage 4) after the appearance of tonofilaments but before the appearance of the first "fetal" keratohyaline granules (KHGs) at 19d (Stage 5). Measurement of the position of MCGs within the cells showed a less marked concentration near the superficial border of the cells than that found at later stages. As KHGs formed, exocytosis of MCGs occurred into the intercellular space immediately deep to the periderm. It is suggested that after 19d (Stage 5) the periderm serves to retain the contents of the MCGs in this space so providing the permeability barrier and that prior to that stage the periderm itself probably provides the permeability barrier of fetal skin.
角质化表皮形成过程中的一系列事件已与胎鼠的年龄和冠臀长相关。在整个妊娠期，表皮的分化在周皮的覆盖下发生。在子宫内生活12天至出生之间定义了十个阶段。膜被颗粒（MCGs）在张力丝出现后的18天（第4阶段）出现，但在19天（第5阶段）第一个“胎儿”透明角质颗粒（KHGs）出现之前。对细胞内MCGs位置的测量显示，与后期相比，细胞浅表边界附近的浓度不太明显。随着KHGs的形成，MCGs通过胞吐作用进入紧邻周皮下方的细胞间隙。有人提出，在19天（第5阶段）之后，周皮起到将MCGs的内容物保留在该空间的作用，从而提供渗透屏障，而在该阶段之前，周皮本身可能提供胎儿皮肤的渗透屏障。
