mammalian development Flashcards
describe the cleavage divisions
they are asynchronous and non-equatorial
what is totipotency and for how long to mammalian embryonic cells retain this capability
cells which can differentiate into any embryonic or extraembryonic cells including germ cells. this is the case up until compaction at 128 days when junctions become tighter and an increase in cellular communication causes cells to lose this potency
what are the two initial structures of the embryo development
the trophectoderm which will develop into extraembryonic membranes and the inner cell mass ICM which will develop into the embryo
what does it mean to say they ICM cells are pluripotent
they can differentiate into any embryonic cells and contribute to the germ line, however they have to be grown within donor embryos as they can’t differentiate into extraembryonic membranes and therefore are not totipotent
what is the difference between ICM and embryonic stem cell ESC
they are both pluripotent. however, ICM cells will differentiate whereas ESCs will retain pluripotency indefinitely, assuming they are in the right culture conditions
what is the first cell fate decision
the choice between ICM or trophectoderm. ICM cells will express Oct4 whilst trophectoblasts will express Cdx2
what is battlefield pluripotency
Cdx2 and Oct2 each upregulate themselves and downregulate the other. as a result their expression is mutually exclusive
what is the second cell fate decision
ICM cells will become either epiblasts (will become the embryo) or primitive endoderm cells PE (will become yolk sac). epiblast cells will express noggin and PE cells will express GATA6
what is FGF signalling
fibroblast growth signalling. this induces the development of the PE and without it all ICM cells will differentiate to epiblast cells
what is the difference between rodent and human embryos
rodent embryos have ‘cup shaped’ epiblast discs whereas humans, and all other mammals, have a flat epiblast disc
what happens at gastrulation
epiblast cells migrate through the primitive streak. the first cells through will become the endoderm and the next cells through will become mesoderm
what is the trilaminar disk
a flat, discoidal embryo which is comprised of the three newly formed germ layers
what causes embryonic folding
the primitive endoderm doesn’t grow but the epiblast continues to. this causes the epiblast to overgrow and fold around it
where does the heart form and how is it moved
the heart and septum transversum develop anterior to the head in the cardiogenic area. folding causes the CA to move ventrally and caudally to locate and orient the heart tube and pericardial cavity
how is the gut tube patterned
by the epiblast overgrowth. it forms the foregut (lungs), the midgut (liver, stomach and pancreas) and the hindgut (intestines)
