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The Endowment for Human Development
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The Folding of the Embryo


3 weeks

From The Biology of Prenatal Development.Buy Now

Script: Between 3 and 4 weeks, the body plan emerges as the brain, spinal cord, and heart of the embryo are easily identified alongside the yolk sac.

Rapid growth causes folding of the relatively flat embryo. This process incorporates part of the yolk sac into the lining of the digestive system and forms the chest and abdominal cavities of the developing human.

All ages referenced to fertilization, not last menstrual period.
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Human Development
Human Development
Heart and Circulatory System
Heart and Circulatory System
The Folding of the Embryo
The Folding of the Embryo
The Folding of the Embryo
The Folding of the Embryo
Heart Development
Heart Development
The Embryo and Yolk Sac
The Embryo and Yolk Sac
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