Formation and Closure of Anterior Neuropore
This period could be extended to 22 somites, because the most advanced embryo, with a copulation age of 9 days 2 hours, had 23–24 pairs of somites. In the mouse, the formation of a new somite pair requires 1–2 hours. I have chosen an upper limit of 20 somites for this stage so that it will correspond to Streeter’s horizon XI.
KeywordsNeural Tube Umbilical Artery Coelomic Epithelium Trophoblastic Giant Cell Uterine Lumen
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