RESUMEN
BACKGROUND: Morphologic characteristics of the human embryonic and fetal periderm according to body region are not very clearly defined. OBJECTIVE: We have tried to Clarify the sequential development of periderm regionally. METHOD: Skin samples were obtained from 12 human embryos and fetuses ranging from 4 to 23 estimated gestational ages(EGA) and divided regionally into scalp, face, back. abdomen, thigh and sale. Specimens were observed by scainning with an electron microscope. RESULTS: Human embryonic end fetal periderm show distinct morphologic changes as follows along its own sequence of development flattened surface, elevated surface, fiormation of incomplete bleb. single bleb stage, multiple-complex bleb stage, formation of regressinjg bieb. Then towards the end of the second trimester, most of thieperidermal cells are completely regressed. Regional variation in peridermal development is not evide!nt during the embryonic period, but earlier development is apparent in the sole, face and scalp especially in the sole compared to other areas during the late first snd second trimester after EGA 9 weeks. CONCLUSION: The periderm, which can be seen only in embryonic and fetal epidermis, shows distinct sequential developmental changeis with regional variation.