Roberts C T, Breed W G
Department of Anatomy and Histology, University of Adelaide, South Australia.
J Reprod Fertil. 1994 Jan;100(1):105-13. doi: 10.1530/jrf.0.1000105.
A light microscope study of the choriovitelline (yolk sac) placenta of the dasyurid marsupial, Sminthopsis crassicaudata, and some comparative observations on that of the didelphid, Monodelphis domestica, were performed. In the former species, the placenta was composed of an invasive bilaminar, avascular, yolk sac and a non-invasive trilaminar, vascular yolk sac. The bilaminar yolk sac placenta had trophoblast giant cells that eroded the maternal epithelium, but there was no evidence of invasion of maternal capillaries; thus, an endotheliochorial placenta was present. In the trilaminar yolk sac placenta, the convoluted chorion followed the contours of the highly folded endometrial epithelium but did not erode it and, therefore, an epitheliochorial placenta was formed. In late pregnancy, the choriovitelline placenta of Monodelphis domestica also had two regions, but the fetal trophoblast did not invade the uterine epithelium in either region. Rather, there were discontinuous areas of adhesion between trophoblast giant cells and uterine epithelium in the trilaminar yolk sac placenta and some extensive areas of adhesion in the attenuated bilaminar yolk sac placenta. The yolk sac placenta in M. domestica, unlike that of S. crassicaudata, therefore appears to be epitheliochorial in the vascular and non-vascular regions.
对袋鼬科有袋动物肥尾袋鼩（Sminthopsis crassicaudata）的绒毛膜卵黄囊（卵黄囊）胎盘进行了光学显微镜研究，并对袋鼹科的家短尾负鼠（Monodelphis domestica）的该胎盘进行了一些比较观察。在前者物种中，胎盘由侵入性的双胚层、无血管的卵黄囊和非侵入性的三胚层、血管性卵黄囊组成。双胚层卵黄囊胎盘有侵蚀母体上皮的滋养层巨细胞，但没有证据表明母体毛细血管受到侵入；因此，存在内皮绒毛膜胎盘。在三胚层卵黄囊胎盘，卷曲的绒毛膜沿着高度折叠的子宫内膜上皮轮廓走行，但不侵蚀它，因此形成上皮绒毛膜胎盘。在妊娠后期，家短尾负鼠的绒毛膜卵黄囊胎盘也有两个区域，但在这两个区域中胎儿滋养层均未侵入子宫上皮。相反，在三胚层卵黄囊胎盘的滋养层巨细胞与子宫上皮之间存在不连续的粘连区域，在变薄的双胚层卵黄囊胎盘中有一些广泛的粘连区域。因此，与肥尾袋鼩不同，家短尾负鼠的卵黄囊胎盘在血管和非血管区域似乎都是上皮绒毛膜型的。
