The embryonic heart begins beating on about day 22-23, accepting blood corpuscles from the yolk sac and pushing blood into the circulation. The embryonic blood begins circulating at the end of the 4th week of development. An Atlas of the Human Embryo and Fetus: A Photographic Review of Human ... - Page 21 by Jan E. Jirasek - 2000 - 144 pages Limited preview -
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