Labels:bulletin board | dialog box | sidewalk | sky | web site | window OCR: Stages and Events 0i Early Human Prenatal Development Stage Time Period Principal Events Fertilized 12-24 hours following Oocyte fertilized zyqote has 23 pairs .of ovulation chromosomes and is genetically distinct Cleavage 30 hours to third Kep Mitosis increases cell number Morula Third to fourth Kep Solid ball o cells Blastocyst Fifth Kep through Hollowed ball forms trophoblast (outside) second week pue inner cell mass which implants ano flattens to form embryonic disc Gastrula End of second week Primary germ layers form Oocvte Iball Iayers
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