17 ore 3 min, 18 apr 2002 anni - Beginning Development

Descrizione:

The menstrual cycle stops due to the increased levels of estrogen and progesterone. These hormones also help the placenta start to form. In this stage, the embryo now has 3 layers. The ectoderm will form into the skin, eyes, inner ears, and the central and peripheral nervous systems. The mesoderm will form into the heart and circulatory system, the beginnings of bones, kidneys, ligaments, and the reproductive system. Finally, the endoderm will develop into the lungs and intestines.

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