cleavage Flashcards
(24 cards)
what is cleavage
24 hours after fertlization, when the zygote initaites rapid mitotic cell divisions
What are blastomeres
smaller daugther cells of the zygote
what encloses the embryo
1st week
zona pellucida
how many blastmores after
24
48
72 hours
2
4
6-12
what is the embryo after four days called and how many blastomeres
morula
16-32
to what does the morula give rise
embryo proper
associated extraembryonic membranes
placenta and related structures
what is the embryonic pole
the side of the blastocyst containing the inner cell mass the other side abembryonic
what happens to the blastomeres at the 8th cell-stage and why?
they flatten, devloping an inside-outside polarity that maximizes cell to cell contact.
what happens to the outer and inner surfaces of the cells strucuture? at the 8th cell stage
inner concave
outer convex
what is the reorganizing of blastomeres called (during flattening at the 8th cell-stage)
the compaction
what is the inner cell mass also called and what is it?
embryoblast, the central placed blastomeres
what is the trophoblast
the cells at the periphery/outisde of the morula.
what is the primary source of the placenta (in the morula)?
trophoblast
how many cells does the morula have by 4 days, and what does it start to do?
aprox. 30
absorb fluid
what happens to the trophoblast at day four (first)
it differantiates into an epithelium in which adjacent cells are tightly adherent to each other.
what is E-CADHERIN
a depostion production of a calcium dependent cell adhesion molecule on lateral cell surfaces
how does the trophoblast adhesion work (2 things)
E-CADHERIN
intercellular junctions
name the intercellualr juntions between trophoblasts.
tight junctions, gap junctions, adherens junctions , and desmosomes
what happens to the trophoblast after adhesion (formation of), result?
formation of na-K pumps
allowing transport of metabolites inside and outside the morula
what is the fluid of the morula called?
blastocoelic fluid
what is the blastocyst cavity and how formed
cavity of the morula, by hydrostatic pressure
when is the cell called a blastocyst (approx day aswell)
when the embryoblast cells form a compaxct mass at on side of the blastocyst cavity
and the trophoblast forms the single layered epithelium
when does the trophoblast and inner cell mass appear (not what day)
at compaction or 8th cell stage
day 4=
day 5=
day 4= morula
day 5= blastocyst
