Embryo : days to remember
Blastocyst:4-5 days after fertilization;
Fertilized ovum reaches uterus in:5-6 days;
Implantation:6-7 days;
Trophoblastic venous sinuses form : 9-11 days;
Cardiovascular system begin to form : 21 days;
Earliest morphological indicator of sex appears: 8-9 weeks;
Oogenesis begins : 11-12 weeks.
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