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Begins to exist when a sperm fertilizes the egg.
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Fertilization
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Joining of Pronuclei
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Occurs when the two pronuclei join together.
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1st Round of Mitosis (Cleavage); 2 cells
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2nd Round of Mitosis; 4 cells
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3rd Round of Mitosis; 8 cells
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16 cells
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Occurs when the zygote becomes a morula.
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Implantation
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64 cell Embryo called a Blastocyst
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Cells break through hard zona pellucida
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Ectopic pregnancy could occur (approximate time)
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hCG begins to be secreted
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Disc with streak on the underside forms the mesoderm
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Neural tube forms
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1st missed period
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Heart begins to beat, arm and leg buds appear, yolk sac makes RBCs
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Face plates forming
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Cleft lip or palate may occur
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Muscles form, bent neck, webbed hands and feet, segmented back
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Fingers and toes separate, eyes and ears formed
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Occurs when all the organs are formed.
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Genitalia begin to differentiate, eyelids fuse, amnion surrounds fetus
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Chorionic villi sampling could be performed
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Amniocentesis could be performed
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Eyes open, fat added under skin, head out of proportion to the body
