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The Endowment for Human Development
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Three-Week Embryo

3 weeks

Three-Week Embryo [Click for next image]
From The Biology of Prenatal Development.Buy Now

Note:

The first hint of central nervous system development (brain and spinal cord) occurs about 18 days after fertilization with the appearance of the neural folds.

Label Key:

1. midbrain
2. forebrain
3. hindbrain
4. somites
All ages referenced to fertilization, not last menstrual period.
Embryo at About 11 Days
Embryo at About 11 Days
Tube Shaped Heart
Tube Shaped Heart
Three-Week Embryo
Three-Week Embryo
Left Lateral View: 3-Week Embryo
Left Lateral View: 3-Week Embryo
Three-Week Embryo
Three-Week Embryo
3-Week Embryo
3-Week Embryo
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