Embryonic membranes and cavities Flashcards
What are the 2 germ layers derived from the embryonic disc?
ectoderm - amniotic epithelium, surrounds amniotic cavity
endoderm - yolk sac epithelium, surrounds yolk sac cavity
Where is the extra-embryonic mesoderm screted from?
trophoblast and yolk sac
What is the chorionic cavity?
cavities formed in the EEM which combine to form one big cavity
What membranes does the EEM give rise to?
- amnion - EEM + amniotic epithelium
2. chorion - EEM + trophoblast
What happens to the cavities at week 6?
amniotic cavity enlarges faster than chorionic and gradually obliterates it
Parts of the chorion
- chorion laeve (smooth) at aembryonic pole
2. chorion frondosum (irregular) at the pole where placenta is developing
What is the placenta derived from?
derivatives of trophoblast
What region of the mother does the conceptus develop in?
decidua basalis - embryo obliterates uterine cavity as it expands
What occurs in the embryo at month 3?
embryo floats in amniotic fluid
amnion and chorion fuse to form the amniochorionic membrane
What are the intraembryonic cavities?
pericardial - heart
peritoneal - abdomen
2x pericardio-peritoneal canals - lungs
Formation of the placenta in the first trimester
syncytio + cyto
lots of mesoderm
few but large villi w/ central fetal vessels
Formation of placenta in the third trimester
sync and isolated cyto cells
little mesoderm
numerous and small villi w/ peripheral fetal vessels
What is the intervascular barrier
tissue layers between maternal and fetal blood
Formation of placenta at term
maternal blood surrounds villous trees
fetal blood lies in vessels in villi, separate
barrier: mainly sync and vascualar endothelium
Placenta conditions
abruption - peels from uterine wall
previa - low - lying, blocking exit (cervix)
accreta - implants too deeply/firmly
