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要说肚脐是怎么形成的，就要先说说脐带。我们都知道每个胎儿都要在母体中孕育十个月左右才会来到这个世界。在这段漫长的时间里，胎儿是如何隔着羊水、羊膜、子宫、腹腔的层层阻隔，获得氧气和营养物质的呢？
原来，在受精卵着床于子宫内膜之后，胚胎的部分胚膜和相邻的母体子宫内膜就会逐渐融合形成胎盘。胎盘与胚胎之间又会逐渐形成包裹着脐动脉、脐静脉、脐尿管的管状结构，
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