Reasons for Diversity of Placental Structure
Reasons for Diversity of Placental Structure
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DOI：
10.1016/j.placenta.2008.09.018
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发表时间：
2009-03-01
期刊：
影响因子：
3.8
通讯作者：
Enders, A. C.
中科院分区：
文献类型：
--
作者：
Enders, A. C.
在不同的真兽亚纲中，许多早期胚胎阶段几乎无法区分。然而，植入阶段和胎盘形态类型差异很大。许多因素有利于这种相互冲突的多样性。1.尽管胚胎发育发生在羊膜腔的隔离中，但孕体的胚外膜与遗传上不同的生物体的子宫密切相关。2.早期条件为发展中的孕体是无氧的，而在后来的发展有效的有氧条件是必不可少的继续增长的胎儿。3.发育中的胚外膜有可能形成两个部分连续的胎盘。卵黄囊可以参与绒毛膜胎盘的形成，包括血管间区，并且随着妊娠的进行可以适应各种非呼吸功能。绒毛膜尿囊胎盘的发育开始于绒毛膜输卵管胎盘的发育，但在取代绒毛膜输卵管胎盘之前，绒毛膜尿囊胎盘的发育可以与绒毛膜输卵管胎盘的发育重叠。胚外膜的最初发育发生在孕体足够小的时候，孕体的营养需求和呼吸需求都不会对妊娠后期的母体机体造成负担。尽管这些发育因素促进了形成定形胎盘的不同方法，但胎盘类型在大多数家庭中是一致的，这表明胎盘结构的分歧伴随着群体之间差异的演变。（D 2009年由IFPA和Elsevier Ltd.出版。
Many early embryonic stages are nearly indistinguishable in different Eutheria. However, implantation stages and placental morphological types vary tremendously. A number of factors favor this conflicting diversity. 1. Whereas embryo development takes place in the isolation of the amniotic cavity, the extraembryonic membranes of the conceptus develop in close association with the Uterus of a genetically different organism. 2. Early conditions for the developing conceptus are anaerobic whereas later in development efficient aerobic conditions are essential for continued growth of the fetus. 3. Developing extraembryonic membranes have the potential to form two partially sequential placentas. The yolk sac can participate in forming a choriovitelline placenta, including an interhemal region, and can be adapted to various non-respiratory functions as gestation proceeds. Development of the chorioallantoic placenta begins later than the choriovitelline placenta but can overlap with this before supplanting it. The original development of the extraembryonic membranes occurs when the conceptus is sufficiently small that neither its nutritional requirements nor its respiratory needs are the burden to the maternal organism that they are later in gestation. Despite these developmental factors promoting different methods of forming the definitive placenta, the placental type is consistent within most families indicating that the divergence in placental structure accompanied evolution of differences between groups. (D 2009 Published by IFPA and Elsevier Ltd.