Hülsman Cindy J M, Gao Hui, Kruepunga Nutmethee, Mommen Greet M C, Köhler S Eleonore, Hikspoors Jill P J M, Lamers Wouter H
Department of Anatomy & Embryology, Maastricht University, Maastricht, The Netherlands.
Department of Anatomy, Faculty of Medicine, Kasetsart University, Bangkok, Thailand.
J Anat. 2025 Feb;246(2):190-204. doi: 10.1111/joa.14139. Epub 2024 Oct 12.
Concomitant with the rupture of the cloacal membrane in the 6th week of development, the intermediate layer of the perineal-skin epithelium thickens. We investigated its distribution and the development of the corresponding subcutaneous compartments in serial sections of female human embryos and foetuses and prepared 3D reconstructions to establish topographic relations. The thick-skin area becomes restricted to the outlets of the genital and intestinal tracts. The clitoris and labia majora become identifiable at ~7 weeks. The mesenchymal mass inside the clitoris soon divides into the glans and the cavernous bodies. The clitoral hood forms between 10 and 14 weeks as a fold of tissue that extends from proximal to distal over the glans. Due to the caudal bending of the clitoral shaft, the labia majora gradually cover the clitoris after ~14 weeks. The labia minora form at ~8 weeks from the ridges of thick-skin epithelium that flank the genital exit. They are continuous ventrolaterally with the clitoral hood and ventromedially with the apex of the cavernous body. Dorsally, their dense subcutaneous mesenchymal core extends to the anal canal. Between 8 and 14 weeks, the urethra lengthens axially, while the vaginal vestibule extends ventrally. In this period, the urethral plate of female embryos is mitotically active but does not increase in volume, which suggests that it contributes to vestibular growth. In conclusion, we observed a temporal correlation between the development of the thick-skin epithelium and that of the external genitals, with a distribution that is reminiscent of the dihydrotestosterone-sensitive skin.
在发育的第6周泄殖腔膜破裂的同时，会阴皮肤上皮的中间层增厚。我们在女性人类胚胎和胎儿的连续切片中研究了其分布以及相应皮下腔室的发育情况，并制作了三维重建模型以确定其拓扑关系。厚皮区域局限于生殖道和肠道的出口处。阴蒂和大阴唇在约7周时可辨认。阴蒂内的间充质团块很快分为阴蒂头和海绵体。阴蒂包皮在10至14周之间形成，是一层从近端向远端延伸覆盖阴蒂头的组织褶皱。由于阴蒂体的尾侧弯曲，大阴唇在约14周后逐渐覆盖阴蒂。小阴唇在约8周时由位于生殖道口两侧的厚皮上皮嵴形成。它们在腹外侧与阴蒂包皮相连，在腹内侧与海绵体顶端相连。在背侧，其致密的皮下间充质核心延伸至肛管。在8至14周之间，尿道轴向延长，而阴道前庭向腹侧延伸。在此期间，女性胚胎的尿道板有丝分裂活跃但体积不增加，这表明它对前庭的生长有贡献。总之，我们观察到厚皮上皮的发育与外生殖器的发育之间存在时间相关性，其分布让人联想到对双氢睾酮敏感的皮肤。
