Second Third Week Flashcards
what does epiplast forms
amniotic cells & amniotic caity
embroblast forms what
epiblast & hypoblast
what is another name for trophoblast
outer cell mass
what does trophoblast form
fetal side of placenta
why do we have little lacunae that occur on the syncytiotrophoblast
ultimately nutrients go into epiblast
what does hypoblast cells do
line the inner lining of yolk sac
transdifferentiate
what is transdifferentiate
change entire cell property
hypoblasts do what regarding migration?
migrate out and form very thick band of extra embrionic mesoderm
what does extra embrionic mesodierm form
fetal side of placenta
once fetal side of placenta forms what happens
little holes form
what happens if lots of holes are formed in extraembryonic mesoderm
it splits into two parts: visceral and parietal
when all the lacune merge together what do they form
one chorionic cavity
what is the outer cavity of yolk sac called
extraembryonic visceral mesoderm
what forms half of the connecting stalk and also coats yolk sac
extraembryonic visceral mesoderm
what forms the connecting stalk
1/2 from visceral and 1/2 from parietal mesoderm
what eventually happens to the visceral and parietal mesoderm
it will go away
in week two what disappears
primary yolk sac
when does yolk sac decrease
week 14-20
why does yolk sac decrease
europlacental circulation takes over
what does embryonic parietal mesoderm help form
secondary chorionic villi
what happens if blastocyst dies but trophoblast does not
trophoblast pumps out more hhg and can potentially give rise to cancer
what 3 major things happen in week 3
primitive streak - definitive
notochord
gastrulation - 3 layers
what happens in primitive streak
where primoridal germ cells go through during development of gametes
where is primtiive streak located
in the back of embryo
where is epiblast layer
on front part
what does notochord do
it doesnt form anything but tells other things what to do
what is gastrulation
differentiation of three germ layers
what 3 germ layers develop (3 layers of trilaminar disk)
intraembryonic ectoderm
intraembryonic mesoderm
extraembryonic endoderm
what is the first sign of gastulation
primitive streak
what does the first population of cells help to form
intraembroyinic endoderm
what does the second population of cells help to form
intraembryonic mesoderm
what forms the floor
the endoderm
what goes in like water and fills up the middle
intraembroyinic mesoderm
what do the third population of cells form
pinched off to form neurotube
what is notocord formed from
mesendermal cells
what does notocord do
tells the overlying ectoderm to form the neuroectoderm
what happens to neuroectoderm
pinches off to form neurotube
what does neurotube form
central and peripheral nervous system
what cells dont migrate ad what do they form (fourth population of cells)
ectoderm
what is the function of allantois
involved in fetal excretion
what takes over the allantois
placenta
what is the tailfold and what does it do
allantosis shoved into connected stalk - the vessels of alantosis (arteries and veins) migrate from allantosis and goes into connecting stalk and forms the umbilical vessels
before neuro tube closes what are the cells around it called
neural crest cells
what is the function of neural crest cells
peripheral nervous system dorsal root ganglia skeletal and musclar parts meningeal coveraings melanocytes in epidermis of skin and hair
where do neural crest cells go
migrate to target organs
what causes hypoblast cells to remodel the primitive yolk sac
endoderm cells coming in and pushing them out
what lines the yolk sac
endoderm
what forms the epithelial lining of gut tube
endoderm
what does endoderm do
forms gut tube & endoethelial lining of all GI tract ecept mouth and distal and anus and lining of respiratory tract, and anything that buds off of GI tract (baldder, lungs)
If it buds off of GI tract, what does it come from
endoderm
paraxial mesoderm ahs what two parts
sclerotome
dermomyotome
what does sclerotome form
axial skeleton (torso)& neurocranium
what is visceral cranium formed from
neural crest cells
what does dermomyotome form
dermis of skin of the back
skeletal muscle of torso and limbs
the skin is formed from ectoderm only - yes or no?
no - outer lining of epitherlium but dermis of skin is formed from dermomyotome
what forms all the skeletal muscles
dermomyotome
urinary system is only formed from what
intermediate mesoderm
the lateral plate mosoderm is split into what two parts
visceral lateral plate mesoderm
parietal lateral plate mesoderm
what forms cardiovascular system
visceral lateral plate mesoderm
what does ectoderm help form
top layer - epithelial lining
where does heart move to
from the dorsal side of embryo to
what does lateral fold pinch off
the yolk sac
where doesnt the lateral fold pinch off
connecting stalk
what does lateral fold pinch off
ventral part of developing embryo except connecting stalk
where does the lateral fold pinch off
vitilointestinal duct
what happens if lateral fold doesnt pinch off
mekel’s diverticulum
what is hydraminios/polyhydramios
too much amniotic fluid
what is oligohydramios
too little amniotic fluid
what is the most common cause of hydramnios
idiopathic (we dont know why)
how can esophageal atresia cause hydramnios
normally baby drinks some amniotic fluid, if esophagus ends, baby drinks it and then it vomits it out, when baby drinks amniot fluid normally baby keeps 1/3 of fluid, if baby throws up fluid and isn’t retaining any then will have too much amniotic fluid
how can esophageal atresia cause hydramnios
normally baby drinks some amniotic fluid, if esophagus ends, baby drinks it and then it vomits it out, when baby drinks amniot fluid normally baby keeps 1/3 of fluid, if baby throws up fluid and isn’t retaining any then will have too much amniotic fluid
what are main causes of oligohydramnio
renal agenesis
amnion rupture due to trauma
urinary obstructive lesions
what is pulmonary hypoplasia
incomplete development of lungs
what can cause pulmonary hypoplasia
oligohydramnio
fetal side of placenta is called what
chorion
why are villi important
effecient gas exchange, want water and gas in and waste out
what are the three types of chorionic villi
primary
secondary
tertiary
as pregnancy continues what villi increase and decrease
primary amount goes down
secondary and tertiary goes up
What is the name of the fetal side of the placenta
chorion/chorionic plate
what makes up the fetal side of the placenta
Chorion= trophoblast layers ((Syncytiotrophoblast (*), Cytotrophophoblasts(**)) and parietal extraembryonic mesoderm
what makes up the maternal side of the placenta
cotyledon - little bumps
decidua
what is major difference b/w tertiary and secondary
tertiary has everything secondary does plus capillary
what happens in fetal period 9-40th week
mainly growth and maturation of tissues, addition of fat
what is different in 11 to 31 weeks
large deposition of fat
when are most organ systems established and functioning
by end of 8th week
two kinds of multiple pregnancies:
dizygotic/fraternal twins
monozygotic/maternal/identical twins
what is another name for identical twins
monozygotic
what is another name for fraternal twins
dizygotic
how do fraternal twins occur
two fertilized zygotes - 2 ovuum are ovulated) have two chorionic sacs, two amnions, two placents, may not be same sex and different morphology
how do identical twins occur
originate from one zygote and are the same sex, genetically identical and very similar in physical appearance
what is chromosome number in blasphomeres
46, 2N
how many chorionic sacs are there in dizygotic twins
2
how many placentas are in dizygotic twins
2
what are the three locations monozygotic twins can occur
separation at blastula containing two blastomeres stage
separation at early blastocyst stage
separation at bilaminar germ disc stage
describe what happens if there is separation at blastula containing two blastomeres
similar to dizygotic twins (2 placenta, etc) but genetic makeup, fingerpreints, sex are similar
morula becomes what
blastocyst
describe what happens when there is separation at early blastocyst stage
inner cell mass splits into two separate groups withint he same blastocyst, two blastocyst have a common placenta, commoon chorionic cavity but separate amnionic sacs
describe what happens at bilaminar germ disc stage to have monozygotic twins
two blastocysts have a single placenta and common chorionic and amnioic cavities
how many placentas are present if separation atbilmaniar germ disc occurs and produces monozygotic twins
1
how many placenta are there if there is separation at early blastocyst for monozygotic twins
1
Which of the following is most likely about embryonic folding?
A. Head fold forces the heart to the dorsal surface
B. Head fold forms the midgut only
C. Laterl fold enlargs the yolk sac
D. Tail fold helps to form primary villi
E. All 3 folds pinch off yolk sac
E
What does head fold form
foregut
what does tailgut form
hindgut
what does lateral fold form
midgut
does the tail fold help to form primary villi
no
do all 3 fold pinch off yolk sac?
yes
what is clinical corrilation if the 3 folds do not pinch off correctly
meckel’s diverticulum
Which of the following is most likely about villi
A: formed from hypoblst cells only
b. primary villi contain only cytotrophoblst cells
c. secondar villi contain synctiotrophoblast and cytotrophoblast cells only
d. tertiary villi contain all the components of secondary villi plus placental barrier
e. tertiary villi decrease in number as pregnancy continues
D
Are villi formed from hypoblast ells only
no
do primary villi contain only cytotrophoblast cells?
no
Where the epiblast and hypoblast fused, what is it called?
prechordal plate
what is the significance of the prechordal plate?
helps establish rostral-caudal orientation (front and back of baby)
what is a hydatiform mole?
what cancer is called if there is no embryo but still a trophoblast
Third epiblast form what?
neuroectoderm
Fourth epiblast form what?
intraembryonic ectoderm
