Development of dermal ridges in the fetus

M Okajima
1975 Journal of Medical Genetics  
This paper describes a new technique to inspect dermal ridges on the dermal surface instead of the epidermal surface. The dermal surface was exposed by chemical treatment and stained with toluidine blue. Dermal ridges are observable by the metachromatic effect of the reagent, which might suggest a close relationship between morphological characteristics and quantitative variations of biochemical components in the connective tissue. Dermatoglyphic features were recognized in fetuses from the
more » ... gestational week. Morphogenesis of dermal components-that is, grooves, primary and secondary dermal ridges, furrows, papillae, and sweat ducts-was examined at various gestational stages. The general law in the developmental sequence of the ridges in different volar areas was also confirmed. Many studies on the dermal ridges have been reported from the standpoint of developmental anatomy. Most of them are concerned with the histological survey of fetuses at various developmental stages. It is, however, not easy with this method to describe morphogenesis of the dermal ridges precisely. A three-dimensional conception of the subject is also required for this purpose. Hale (1952) reconstructed the three-dimensional structure of the under-surface of the epidermis for various fetal stages with stained serial histological sections and illustrated the morphogenesis of the dermo-epidermal junction. His study contributes much to the understanding of ridge formation, but this is a time-consuming method and gives no information about dermatoglyphic patterns. Simple methods of dermatoglyphic examination are printing with ink, casting, and direct inspection of the epidermal surface. Prints are usually not obtainable from fetuses because the epidermal ridges are too fine and not sufficiently elevated. In earlier fetuses, the epidermal surface is flat, and the ridges are distinguished as the refraction of light through the fairly transparent epidermal tissue rather than the elevation of the epidermis. Therefore, in fetuses the direct inspection with a stereo-microscope is better than trying to obtain prints. Miller (1968) inspected dermatoglyphics of human fetuses directly and classified dermal patterns in specimens from the latter half of gestation with no special treatment or application of a depilatory cream. Another approach to the inspection of dermal ridges is a maceration technique. The epidermis can be abraded from the dermis by various procedures and sometimes incidentally during decomposition or the preservation of cadavers. Blaschko (1887) demonstrated ridge arrangements on the under-surface of epidermis, treated with a weak alcohol, abraded from the finger tip of a fetus in the fourth month. A systematic investigation of the under-surface of abraded epidermis was made by Fleischhauer and Horstmann (1951/1952) for fetuses of various crown-rump measurements. The epidermis was abraded with 1% acetic acid and the dry specimen was produced by treatment with turpentine. In this study, morphological differentiation of the dermo-epidermal junction was clearly seen. Specimens used for this technique must be fresh, and those fixed in formalin or alcohol are no use. In these specimens, an inspection of the whole surface, which is essential for the dermatoglyphic examination, may be disturbed by contraction and wrinkling of the epidermal tissue during treatment. On the other hand, Chacko and Vaidya (1968) observed the surface of the dermis using macerated volar skins from human newborns and adults and 243
doi:10.1136/jmg.12.3.243 fatcat:hf66tdkzxjhpfdx5leggckrscm