-
Start
Fertilization -
Fertilized Egg
Begins to exist when one sperm makes it through the zona pelucida leading to conception. -
Day 1, Hour 12
Pronuclei join together -
Zygote Stage Begins
Occurs when the pronuclei fuse. -
Day 2, 30-36 Hours
First round of mitosis (cleavage) -
Day 2, 40 Hours
Second round of mitosis -
Embryo Stage Begins
Occurs when the mass of cells reaches eight and is called a morula. -
Day 3, 55 hours
Third round of mitosis -
Morula formed
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Hatching
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Day 6
64 cell embryo called a blastocyst -
Day 8 -- Prior to Implantation
Ectopic pregnancy could occur -
Day 9
Implantation -
Day 12
hCG begins to be secreted -
Day 12
Disk with streak on the underside forms mesoderm -
Day 15
First missed period -
Day 15
Neural tube forms -
Day 21
Heart begins to beat, arm and leg buds appear, yolk sac makes RBCs -
Days 34, 35, 36
Face plates forming -
Days 34, 35, 36
Cleft lip or palate may occur -
6th Week
Muscles form, bent neck, webbed hands and feet, segmented back -
7th Week
Fingers and toes separate, eyes and ears formed -
Fetal Stage Begins
Occurs when all of the organs have been formed. -
Day 50
Genitalia begins to differentiate, eyelids fuse, amnion surrounds fetus -
10 Weeks
Chorionic villi sampling could be performed -
Week 14
Amniocentesis could be perfomed -
6-7 Months
Eyes open, fat added under skin, head out of proportion to the body
