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Fertilized Egg
Begins to exist when the sperm reaches the egg and fertilizes it, mixing it's genetic makeup with the eggs. -
Start
Fertilization -
12 hours
Pronuclei join together -
Zygote Stage Begins
Occurs when the 23 chromosomes from the male and 23 chromosomes from the female join together. -
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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Embryo Stage Begins
Occurs when the egg is implanted into the uterus and the developing of the embryo continues. -
Day 6
64 cell embryo called a blastocyst -
Hatching
This is when the blastocyst hatches from the zona pellucida. -
Day 8-10
Implantation -
Day 10
Ectopic pregnancy could occur -
Day 12
hCG begins to be secreted -
Day 12
Disc with streak on the underside forms mesoderm -
Day 15
First missed period -
Day 14-22
Neural tube forms -
Day 21
Heart begins to beat, arm & leg buds appear, yolk sac makes RBCs -
Day 34, 35, 36
Face plates forming -
Day 35
Cleft lip or palate may occur -
Week 6
Muscles form, bent neck, webbed hands and feet, segmented back -
Week 7
Fingers & toes separate, eyes & ears formed -
Fetal Stage Begins
Occurs when all organs are formed, muscles are developing, arms and legs are forming and eyes/face are also forming. -
Day 50
Genitalia begins to differentiate, eyelids fuse, amnion surrounds fetus -
Week 9-11
Chorionic 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
