Chapter 12 mammals Flashcards
Mammalian development leads to _______ cleavage
rotational
The first division in mammals is _______ while the second cleavage is ______
meridional
asymmetrical
- one is meridional while the other is equitorial
In mammalian cleavage, loosely connected cells of the blastula “huddle” together in a process called _______
compaction
Expression of _______ causes compacting cells to form a compact ball of cells (what allows compaction?)
E-cadherins
Compacting cells are stabilized by _______ junctions
tight
- seals off the inside of the mass from the outside
Compacting cells form _______ junctions, allowing communication via small molecules
gap
The Morula (_____ cell stage), is where the first real differentiation event, and is composed of what 2 parts?
Inner cell mass (ICM, epiblast)
- pluripotent, becomes embryo
Trophectoderm (trophoblast)
- becomes chorion
In the beginning of trophoblast, ICM determination, all cells express _______
Cdx2 & Oct4
Trophoblast ICM determination:
Trophoblast cells continue to express Cdx2 as activated by _______
Yap
Trophoblast ICM determination:
In trophoblast cells, Yap binds to _______ as a cofactor required for Cdx2 transcription
Tead4
Trophoblast ICM determination:
ICM receive the _______ signal that activates the _______ kinase
Hippo
lats
Trophoblast ICM determination:
Lats phosphorylates and inactivates _______ so that it cannot induce the Cdx2 expression
Yap
Describe the process of determining trophoblast cells?
1) Yap binds to Tead4
2) Cdx2 is transcribed blocking Oct4
3) lack of surrounding cells leads to a blockage of the HIPPO signal so that Lats is not activated
- how it differentiates from ICM
- ultimately Cdx2 expression determines (cuz Oct4)
_______ is created by trophoblast cells secreting fluid into the morula, creating space
blastocoel
the process of creating blastocoel by trophoblast cells secreting fluid into the morula is called _______
cavitation
Cavitation requires the action of _______ and _______ pumps to increase ion concentration outside of trophoblast cells
Na+/H+ antiporter
Na+/K+ ATPase
- both pump Na+ out of trophoblast cells
The _______ remains in place during the embryo’s journey through the oviducts towards the uterus
zona pellucida
- prevents premature implantation in the walls of the fallopian tubes
Once in the uterus, the blastocyst hatches free from the zona pellucida by digesting a small hole with a _______ and squeezing through
trypsin-like protease
_______: implantation in any location other than the endometrial lining of the uterus
ectopic pregnancy
- also called tubal pregnancy
- can kill the mother via hemorrhaging
The blastocyst caught by _______ of trophoblast cells binding to endometrial sulfated polysaccharides
L-selectin
After binding of L-selectin and endometrial sulfated polysaccharides, secondary binding of _______ and _______ “dock” the embryo into the uterus
integrins and P-cadherins
Once bound to the endometrium, the embryo then secretes several proteases that allow it to burrow into the lining of the uterus. A process called _______
implantation
Implantation is mediated by signals involving _______ protein signals
Wnt
What are the 3 enzymes that digest the ECM of the uterine tissue?
1) Collagenases
2) Stromelysin
3) Plasminogen activator
Since mammals don’t have a large yolk, a _______ must be established with the mother to exchange nutrients
placenta
What are the 2 parts of the placenta?
1) Chorion
- from trophoblast, Fetal portion
2) Decidua
- from uterine lining, maternal portion
The decidua is formed from uterine lining cells induced by signals from the _______
chorion
The inner cell mass cells divide into the _______
bilayer germinal blastodisk
- will delaminate to form epiblast and hypoblast
Hypoblast will delaminate to line the blastocoel and form the _______ producing the _______
extraembryonic endoderm
yolk-sac
the epiblast will separate into what 2 parts?
1) embryonic epiblast
2) amniotic ectoderm
from the epiblast:
_______: will form all the tissues of the developing embryo
embryonic epiblast
from the epiblast:
_______: will form the lining of the amniotic cavity
amniotic ectoderm
- secrets amniotic fluid that fills the amniotic cavity. Acts as a shock absorber and prevents desiccation
_______: original trophoblast cells that adhere to the endometrium, and remodel maternal vasculature
cytotrophoblast
_______ formed from cytotrophoblasts that undergo karyokinesis without cytokines creating multinucleated cells
syncytiotrophoblast
- remodel
- push embryo deeper into endometrium
- contact mother blood vessels
_______ follows syncytiotrophoblasts and continues making connections with maternal tissue and vasculature. Will form the Umbilical Chord
extraembryonic mesoderm
_______: identical twins
monozygotic twins
- one egg
Split before formation of the trophoblast will lead to twins that have _______ chorion and _______ amnion
own
own
Split after formation of the trophoblast will lead to twins that have _______ chorion and _______ amnion
shared
own
Split after amnion formation will lead to twins that have _______ chorion and _______ amnion
shared
shared
_______: nonidentical twins
dizygotic twins
- two egg
_______: an individual containing cells from two or more original embryos
chimera
- mouse ex with three different 8cell blastulas
What are the 2 examples of human chimeras?
1) fusion of non-identical twins
2) somatic chimeras (blood type)
_______ twins are identical twins who develop with a single _______ from a single fertilization
Conjoined
placenta
- will always be same sex, and 3F:1M chance
Conjoined twins:
_______: anterior union of the upper half with a shared heart
thoracopagus
- most common
Conjoined twins:
_______: anterior union of mid trunk
omphalopagus
Conjoined twins:
_______: posterior union of the rump
pyropagus
Conjoined twins:
_______: lateral union of the lower half of the body, variable
parapagus
Conjoined twins:
_______: cranial union only
craniopagus
- least common
What are the two rare forms of conjoined twins:
_______: asymmetrical conjoined twins, one small and less formed and dependent on the other
parasitic twin
What are the two rare forms of conjoined twins:
_______: an imperfect fetus is contained completely within the body of its sibling
fetus in fetu
A/P axis formation in mammals:
The Posterior end has high concentrations of _______, ________, _______, _______
1) Wnt
2) Bmp
3) FGF
4) Retinoic acid
Retinoic acid is _______ at the posterior end and _______ at the anterior end
synthesized
degraded
A/P axis formation in mammals:
The Anterior end has high concentrations of _______, and _______
Wnt inhibitors
BMP
A/P patterning by hox genes in mammals have equivalent genes/gene clusters called _______
paralogues/paralogous
All mammals have _______ of the HOX complex in haploid genome on 4 chromosomes
4 copies
- HOXA, HOXB, HOXC, HOXD in humans
responsive to a wnt gradient
Mammals are not completely _______ symmetrical
bilaterally
- heart, spleen, stomach, liver, intestines, lungs
Major regulatory step: activation of _______ and _______ TF’s on the left side of the lateral plate mesoderm
Nodal
Pitx2
_______ is found in all 4 organisms and marks the initiation of the blastopore
Spemann-Mangold organizor (SMO)
