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The Endowment for Human Development
The Endowment for Human Development
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Blood Cells and Bone Marrow


3 months, 3 weeks

From The Biology of Prenatal Development.Buy Now

Script: By 15 weeks, blood-forming stem cells arrive and multiply in the bone marrow. Most blood cell formation will occur here.

All ages referenced to fertilization, not last menstrual period. One month = 4 weeks.
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Blood Cells and Bone Marrow
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