Human Embryogenesis Flashcards
when does oocyte get stalled
second meiotic division
Capactiation
head of sperm can release enzymes
- occurs in uterus/uterine tube
- 6 hours of exposure
acrosome reaction
allows sperm to petite corona radiate and zone pellucida
-degrades zona poluza to allow 1 sperm to fuse to PM of oocyte
sperm fuse with oocyte
causes Ca concentration increase (diffuses into oocyte)
-causes corticol reaction
Corticol reacion
vesicles in presynaptic membrane to fuse in
corticol granulas cause changes in zona pellucida preventing polymspermia-ensure no multiple sperm
when does oocyte complete 2nd meiotic division
when sperm extrudes contents into oocyte (nuclei,s centrosome and mts)
-ALL OTEHR ORGANELLES ARE FROM MOM
When does zygotic trx occur
3 weeks, all else occurs with maternal mRNA
when does fist mitotic division occur
response to sperm fusing to oocyte
what space do first several mitotic division occur+ how do they differ
inside zone pellucid-they are also identical
Ectopic preganacy
implantation in any place other that uterun
uterine tube terminates in
ampulla-most common place of ectopic reg
fimbrae-caress ovary
=open up into GI tract-peritoneal cavity
Placenta forming on cervix
many problems-eventually gets torn
What causes uterine lining changes
placenta formation
where are two common sites of ectopic preg
ampulla of uterine tube
recouterine ch-most common peritoneal cavity place
blastocyst strcutre
inner cell mass-embryoblast and trophoblast
- embryoblast becomes embryo
- aka embryonic stem cells
- trophoblast becomes placenta
how does trophoblast become placenta
becomes huge cell with many nuceli-syncitio
-produces and releases HCG (hormone)
0HCG levels rise at implantation
-hormione reg tests look for rise in HCG
syncytiotrophoblast
produces HCG
invades uterine lining and induces vascular changes
what happens when synctioblast invades
embroblast differentiates into epiblast and hypoblast
-epiblast is more dorsal (posterior)
cytotrophoblast
no nutrients-get nutrients from maternal fluid
- primitive yolk sac
- eventually biomes primary villi
Lacunae
formed from syncytiotrohphoblast
- hollow spaces
- fill with blood
Epiblast vs hypoblast + wjere adjere
cell layers in developing embryo
epiblast-posterior/dorsal-aminiotic caivty is more dorsal than epiblast
hypobast-anterior+ventral
adjere at buccopharyngeal (cranial) and cloacal (caudal) membrane
-WHEN embryo TRX BEINGS
Primitive yolk sac
from cytotrphoblast
dives in tear drop formation into secondary yolk sac (suspended from connecting yolk sac)
and cyst(which develop ointo microvilli_
4th week
zygotic trx beings
gastrulation starts
primitive streak appears at caudal end of dorsal surface of epiblast
all sides defined
Now called an embryo
Primitive node
appears at cranial end of primitive streak
Cells here have single, solitary, motile cilia
Fluid here has SHH-sets up assymetry
Motile cilia in primitive node
move right to left
- move vesicles and release thier contents (shh)
- cuases gene expresión changues on left vs right
Sidus inversus
everything reverses-cilia beat other way
Defects in cilia at promitive node
no assymetry-many problems such as deafness, sids inverses, death, kidney diseases
Fate of primitive streak cells
delaminate-migrate between epiblast and hypoblast-establish mesoderm
Some cells will invade hypblast and replace it to establish endoderm
All epiblast will become ectoderm
-wil not invdade buccopharyngeal or cloacal membrane
Fate of epiblast cells in primitive node
delaminate and establish middling notochord between endoderm cranial to primitive streak
