-
Hour 1
Fertilization -
Fertilized egg
occurs with fertilization and is known as such for the first 12 hours -
Hour 12
pronuclei join together -
zygote stage begins
occurs when the nuclear membrane of the ovum disappears and 23 male chromosomes meet 23 female chromosomes. both nuclei double to 46 chromosomes and then fuse. -
hour 30
first round of mitosis (cleavage) -
hour 40
second round of mitosis -
hour 50
third round of mitosis -
embryonic stage begins
begins when the third cleavage occurs and forms a morula -
morula formed
-
day 6
64 cell embryo now called a blastocyst -
day 8
implantation -
day 10
ectopic pregnancy could occur -
hatching
-
day 12
disc with streak on the underside forms mesoderm -
day 12
hCG begins to be secreted -
day 15
first missed period -
day 16
neural tube forms -
day 22
heart begins to beat, arm and leg buds appear, yolk sac makes RBCs -
day 35
face plates forming -
day 36
cleft lip or palate may occur -
week 6
muscles form, bent neck, webbed hands and feet, segmented back -
week 7
fingers and toes separate, eyes and ears formed -
day 50
amniocentesis can be performed -
day 50
genitalia begins to differentiate, eyelids fuse, amnion surrounds fetus -
fetal stage begins
occurs when all organs are formed -
week 9
chorionic villi sampling could be performed -
month 6
eyes open, fat added under skin, head out of proportion to the body
