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Beginning
Fertilization -
Fertilized Egg
Begins to exist when sperm reaches the egg -
12 hours
Pro-nuclei join together -
Zygote Stage Begins
Occurs during the first 2 weeks of development and moves along the Fallopian tube towards the uterus. The ovum disappears and it is the making of 23 chromosomes preparing to divide. -
30-36 hours
First round of mitosis (cleavage) -
40 Hours
Second round of mitosis -
50-60 Hours
Third round of mitosis -
Morula Formed
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Embryonic Stage Begins
Occurs when the egg is divided into morula before it becomes a blastocyst. -
6th Day
64 cell embryo called a blastocyst -
Hatching
-
8-10 days
Implantation -
10 Days
Ectopic pregnancy could occur -
Day 12
Disc with streak on the underside forms mesoderm -
12th Day
hCG begins to be secreted -
Day 15
First missed period -
14-22 Days
Neural tubes forms -
Day 21
Heart begins to beat, arm & legs buds appear, yolk sac makes RBC's -
Days 35
Cleft lip or palate may occur -
Day 34, 35, 36
Face plates forming -
Week 6
Muscles form, bent neck, webbed hands and feet, segmented back -
Fetal stage begins
Occurs when all organs are formed and are prepared to differentiate. -
Week 7
finger & toes separate, eyes & ears formed -
Day 50
genitalia begins to differentiate, eyelids fuse, amnion surround fetus -
Week 9
chronic villi sampling could be performed -
Week 14-15
amniocentesis could be performed -
6-7 months
Eyes open, fat added under skin, head out of proportion to the body
