Key concepts: Gastrulation Flashcards
conditions
spontaneous abortion
describe what happens to the trophoblast before gastrulation
cytotrophoblast is well defined, nucleus is in the cell
cells start proliferating out of the zona pellucida, into the uterine lining
cell membranes start to disintegrate and forms a fluid made from cell nuclei and cytoplasm
when the cytoplasm fuses it forms the syncytiotrophoblast which isn’t well defined
eventually where will the syncytiotrophoblasts connect
to the maternal blood vessels
definition of gastrulation
where the blastula forms a gastrula
bilaminar disc to trilaminar disc
layers of the bilaminar disc
epiblast
hypoblast
what is the bilaminar disc formed by
the embryo blast
cavity below the bilaminar disc
primitive yolk sac
cavity above the bilaminar disc
amniotic cavity
what is found on the epiblast layer
the prochordal plate
what is the prochordal plate
where the epiblast and hypoblast layers are fused
what is the top of the bilaminar disc called
cranial end
what is the bottom of the bilaminar disc called
caudal end
how is the primitive streak formed
singalling processes occur
causing the thickening of an area of the epiblasts
primitive streak forms
with a nob on the cranial end= primitive node
process of gastrulation
cells in centre of primitive streak and node die
forms cavity
cells at edge of primitive streak secrete FGF-8 laterally
FGF-8 binds to FGF-R on nearby epiblast cells
activates SNAIL-1
SNAIL-1 inhibits E cadherins
allows epithelial migration
cells migrate towards the primitive groove and pit
cells migrate through the primitive groove to the hypoblast layer
hypoblast is replaced by these epiblast cells= endoderm
epiblasts release more FGF-8= more epiblast cells
come down the sides ontop of the endoderm
forms mesoderm
original top layer= ectoderm
layers of the trilaminar disc
ectoderm
mesoderm
endoderm
