Fertilization of an egg by a sperm
   occurs in the oviduct.
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   The  resulting  zygote  begins several rounds of cell division without
   growth in a process called cleavage.
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   Division  of  cells gives rise to a blastocyst, a ball of cells with a
   cavity.
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   The blastocyst implants in the wall (endometrium) of the uterus.
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   The  outer  layer  of  the blastocyst (trophoblast), together with the
   endometrium, forms the placenta.