大家知道，耳朵发育的早期特征，是胚胎外层膜的增厚，这层膜也叫外胚层。

We can see the early signs of ear development Start with the thickening of the outer layer of the embryo, this layer is called the ectoderm.

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外层细胞发育成厚厚的膜并最终包裹着胚胎盘，细胞以成千上万的倍数增长并最终形成胚胎。

The outer cells become thin membranes that form around the baby.The cells multiply thousands of times and move to new positions to eventually become the embryo (pronounced: em-bree-o).

youdao

外层细胞发育成厚厚的膜并最终包裹着胚胎盘，细胞以成千上万的倍数增长并最终形成胚胎。

The outer cells become thin membranes that form around the baby. The cells multiply thousands of times and move to new positions to eventually become the embryo (pronounced: em-bree-o).

youdao

We can see the early signs of ear development Start with the thickening of the outer layer of the embryo, this layer is called the ectoderm.

大家知道，耳朵发育的早期特征,是胚胎外层膜的增厚，这层膜也叫外胚层。

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