Division of Animal Sciences, College of Agriculture, Food, Natural Resources, S138 Animal Science Research Center, University of Missouri, Columbia, MO, USA.
Division of Animal Sciences, College of Agriculture, Food, Natural Resources, S121 Animal Science Research Center, University of Missouri, Columbia, MO, USA.
Adv Anat Embryol Cell Biol. 2021;234:129-154. doi: 10.1007/978-3-030-77360-1_7.
In comparison to many other mammalian species, ruminant ungulates have a unique form of placentation. Ruminants initially display an epitheliochorial type of placentation; however, during the period of placental attachment, trophoblast giant binucleate cells (BNC) develop within the chorion to migrate and fuse with the uterine surface epithelium to form syncytial plaques. Binucleate cell migration and fusion continues throughout pregnancy but never appears to breach the basal lamina, beneath the uterine surface or luminal epithelium. Therefore, the semi-invasive type of placentation in ruminants is classified as synepitheliochorial. The endometrium of ruminant species also contains unique specialized aglandular structures termed "caruncles" in which the chorioallantois (cotyledons) interdigitates and forms highly vascularized fetal-maternal "placentomes." This chapter will discuss the current knowledge of early conceptus development during the peri-attachment period, establishment of pregnancy, conceptus attachment, and placentation in ruminant ungulates. The features of placentomes, BNCs, fetomaternal hybrid cells, and multinucleated syncytial plaques of the cotyledonary placenta of ruminant species will be reviewed to highlight the unique form of placentation compared to the placentae of other artiodactyls.
与许多其他哺乳动物物种相比，反刍动物具有独特的胎盘形式。反刍动物最初表现出上皮绒毛膜胎盘类型；然而，在胎盘附着期间，滋养层巨核细胞（BNC）在绒毛膜中发育，迁移并与子宫表面上皮融合形成合胞体斑块。双核细胞迁移和融合贯穿整个妊娠过程，但从未出现在基底膜下，在子宫表面或腔上皮下。因此，反刍动物的半侵袭性胎盘类型被归类为上皮绒毛膜胎盘。反刍动物的子宫内膜还包含独特的专门无腺结构，称为“caruncles”，其中绒毛膜尿囊（子叶）相互交织并形成高度血管化的胎儿-母体“胎盘体”。本章将讨论反刍动物围附着期早期胚胎发育、妊娠建立、胚胎附着和胎盘形成的最新知识。胎盘体、BNC、胎母杂种细胞和绒毛膜胎盘多核合胞体斑块的特征将被回顾，以突出与其他偶蹄动物胎盘相比的独特胎盘形式。
