2：第3周

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<td width="33%">结构</td>

<td width="33%">具体时间</td>

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<td width="34%">心血管系统</td>

<td width="33%">胚内血管发生+胚内外血管连接</td>

<td width="33%">18-20</td>

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<td width="34%">&nbsp;</td>

<td width="33%">原始心脏形成</td>

<td width="33%">18-22</td>

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<td width="34%">泌尿系统</td>

<td width="33%">&nbsp;</td>

<td width="33%">&nbsp;</td>

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<td width="34%">生殖系统</td>

<td width="33%">&nbsp;</td>

<td width="33%">&nbsp;</td>

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<td width="34%">消化系统</td>

<td width="33%">&nbsp;</td>

<td width="33%">&nbsp;</td>

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<td width="34%">呼吸系统</td>

<td width="33%">&nbsp;</td>

<td width="33%">&nbsp;</td>

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<td width="34%">颜面</td>

<td width="33%">&nbsp;</td>

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