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The Endowment for Human Development
The Endowment for Human Development
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Heart and Circulatory System


3 weeks

From The Biology of Prenatal Development.Buy Now

Script: As the first blood cells appear in the yolk sac, blood vessels form throughout the embryo, and the tubular heart emerges.

Almost immediately, the rapidly growing heart folds in upon itself as separate chambers begin to develop.

The heart begins beating 3 weeks and 1 day following fertilization.

The circulatory system is the first body system, or group of related organs, to achieve a functional state.

All ages referenced to fertilization, not last menstrual period.
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Early Embryonic Development
Early Embryonic Development
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
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