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The Endowment for Human Development
The Endowment for Human Development
Improving lifelong health one pregnancy at a time.
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Slideshow: Early Events

Four-Cell Human Embryo

#13, Slide 5 of 24

48 hours

From The Biology of Prenatal Development.Buy Now

Label Key:

1. perivitelline space
2. zona pellucida
3. blastomeres
All ages referenced to fertilization, not last menstrual period.
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