Roberts R Michael, Green Jonathan A, Schulz Laura C
C.S. Bond Life Sciences CenterUniversity of Missouri, Columbia, Missouri, USA Division of Animal SciencesUniversity of Missouri, Columbia, Missouri, USA
Division of Animal SciencesUniversity of Missouri, Columbia, Missouri, USA.
Reproduction. 2016 Nov;152(5):R179-89. doi: 10.1530/REP-16-0325. Epub 2016 Aug 2.
The very apt definition of a placenta is coined by Mossman, namely apposition or fusion of the fetal membranes to the uterine mucosa for physiological exchange. As such, it is a specialized organ whose purpose is to provide continuing support to the developing young. By this definition, placentas have evolved within every vertebrate class other than birds. They have evolved on multiple occasions, often within quite narrow taxonomic groups. As the placenta and the maternal system associate more intimately, such that the conceptus relies extensively on maternal support, the relationship leads to increased conflict that drives adaptive changes on both sides. The story of vertebrate placentation, therefore, is one of convergent evolution at both the macromolecular and molecular levels. In this short review, we first describe the emergence of placental-like structures in nonmammalian vertebrates and then transition to mammals themselves. We close the review by discussing the mechanisms that might have favored diversity and hence evolution of the morphology and physiology of the placentas of eutherian mammals.
胎盘的精确定义是由莫斯曼提出的，即胎膜与子宫黏膜并列或融合以进行生理交换。因此，它是一个专门的器官，其目的是为发育中的幼体提供持续支持。根据这个定义，除鸟类外，胎盘在每一个脊椎动物类别中都有进化。它们在多个场合进化，通常是在相当狭窄的分类群中。随着胎盘与母体系统联系得更加紧密，以至于受精卵广泛依赖母体支持，这种关系导致了冲突加剧，从而推动双方的适应性变化。因此，脊椎动物胎盘形成的故事是一个在大分子和分子水平上趋同进化的故事。在这篇简短的综述中，我们首先描述非哺乳动物脊椎动物中胎盘样结构的出现，然后过渡到哺乳动物本身。我们通过讨论可能有利于多样性以及因此有利于真兽类哺乳动物胎盘形态和生理进化的机制来结束这篇综述。
