Embryology

Front 1

conceptus stage

Back 1

in ampulla

Front 2

morula stage

Back 2

compact ball of cells

Front 3

blastula stage

Back 3

lumen develops and fluid is pumped in

Front 4

embryonic fold

Back 4

inner cell mass is formed gives rise to the entire embryo; embryoblast gives rise to the placenta

Front 5

implantation (day 6)

Back 5

trophoblasts forms 2 layers
Syncytiotrophoblast – invasive multinucleated cells.
Cytotrophoblast – proliferative layer provides more trophoblasts.

Front 6

bilaminar germ disc

Back 6

derived from the blastocyst which contain the epiblast and the hypoblast

Front 7

two cavities formed in the 2nd week

Back 7

amionic (dorsal to epiblast)
yolk sac (ventral to the hyperblast)

Front 8

2 layers of extraembryonic somatic mesoderm

Back 8

Extraembryonic splanchnic mesoderm-
layer around yolk sac

Extraembryonic somatic mesoderm – layer around the amnion and inner surface of the cytotrophoblast
join to form umbilical cord

Front 9

ectopic pregnancy

Back 9

invasive nature of the syncytiotrophoblast cause embryo to implant abnormally outside of the uterus

Front 10

gastrulation

Back 10

in week 3 cells of the bilaminar disk migrate forms 3 germ layers mesoderm,endoderm,ectoderm

Front 11

3 layers of placental villi

Back 11

Outer-syncytiotrophoblast
Inner-chorionic mesoderm
Middle – cytotrophoblast

Front 12

fate of cell surrounding primitive streak

Back 12

Caudal segments – form extraembryonic mesoderm
Cranial segments – from lateral plate, intermediate mesoderm, and paraxial mesoderm