Embryology

Question 1

Basic embryology

Answer 1

Fertilised zygote goes under division and becomes morula. Travels down uterine tube and enlarges with extraembryonic coelum combined is blastocyst. Goes down uterine tube and implants approx day 6 into uterus.

Outer layer is trophoplast=placenta
Inner layer is embryoblast= baby

Week 2 fertilisation embryoblast forms 2 layers, outer columnar epiblast and inner cuboidal hypoblast. 2 cavities appear- amniotic cavity (epiblast) and yolk sac (hypoblast)
Both surrounded by extraembryonic coelom except where embryoblast connected to trophoblast by connecting stalk aka umbilical cord

Question 2

What does ectoderm, endoderm and mesoderm form from?

Answer 2

All form from epiblast
At the primitive steak end form 2 layers mesoderm (next to epiblast) and endoderm (adjacent)

Remaining epiblast cells form ectoderm

Between the endoderm and ectoderm the notocord forms (cephalad) and cloacal membrane (caudal)

Neural tube is from indentation in ectoderm overlying notocord from neural groove. Further cells from edges form neural crest.