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The fusion of between egg and the sperm occurs, forming a zygote.
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The blastocyst hatches out of the protective zona pellucida. The hatching allows an increase in growth, access to uterine nutrient selections, and blastocyst adhesion to the uterine lining.
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The embryo adheres to the wall of the uterus. By this adhesion, the embryo receives oxygen and nutrients from the mother.
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The heart starts to beat during day 23.
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The left and the right lung buds start to push into the pericardioperitoneal canals (primordia of the pleural cavity).
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The retinal pigmentation in the eyes starts to form.
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The heart separation of cardiac outflow occurs. The aortic arch and the pulmonary aorta forms.
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The chorionic cavity is now lost by fusion with the expanding amniotic cavity.
