8/18 Embryo Foundations Flashcards
How are the primordial germ cells unique as compared to other cells
The are unilique in their motility and their potency or ability to create all different types of cells
How does the migratory destination of a primordial germ cells affect third unique properties.
The final location in the genital ridge will suppress he motility and he potency of the cells…otherwise they develop horrible tutors
What is meiotic reduction
The reduction height he first meiotic division of the chromosome number to 23 from 46 thus creating haploid a
What are the main goals of gametogenesis?
Meotic reduction
Recombination
Morphological dofferentiation of gametes to prep for fertilization
Cytoplasmic localization of materials to prep for development
What is the major morphological change that results in many I the common abnormalities such as Down syndrome
Nondisjunction
Describe Nondisjunction
Recombination occurs then meiotic reduction ten cell division to create two haploids if Nondisjunction then either father and mother chromosomes don’t desperate or duplicated chromosomes don’t separate in the subsequent step resulting in germ cells that have too many or too few of a given chromosome
What is the result of Nondisjunction
Aneuplioidy Down's syndrome 21*3 Turners syndrome monosomy of the x Klinefelters xxy Patau syndrome trisomy 13 Edwards syndrome trisomy 18
what hormone causes the differentiation of the pgc
tstoserone
why is the spermatids considered syncytia?
they develop as a gropu where they share the same cytoplasm therefore nucleus is plural in a shared cytoplasm.
why lmight a reason be for te increaseinthe occurance of autism in the last few decaces
the incdreasing age of fahers as fathers age they have a higher riskof abnormal sperm and geetic abnormalities
what happans when the pgc in a female reach the genital cleft or the gonads
they divie to 7,000,000 primary ocytes by 5th fetal month , then lose most to about 2,000,000. and these replicate DNA and arrest, then are surrounded by follicle cells. puberty starrts with 400,000 oocyes.
described the female menstral cycle
fsh up a little then the folicle mature and LH peak and the folicle release egg in ovvulation and form the corpus luteum. this will be viable for 14 days then degenerate. meanwhile the estrogen peaks with the LH and builds the uterin wall causin progesterone to peak and the wall to then degenerate and stuff off. Then menstral cycle
When would a second meiotic division take place in the eggs?
Only following fertilization
What is the corpus lotum
The ring of folicle cells that surround the oocyte
The oocyte has all that is needed for cell differentiation and control how do we know this
Because cloning worked with dilly the sheep
What are some of the regulatory goals of fertilization
Same species No polyspermy Robust sperm fertilize Activate the egg Restore the diploid state
How ensure same species fertilize
Behavior and biogival such as capacitation or loss o the cholesterol head in genital tract
Name three phases of fertilization
Penetration of the cumulus oophorus
Adhesion to and digestion of zona pellucida and the fusion of the egg and the sperm plasma membrane
How does the egg prevent polyspermy?
Cortical reaction of the egg that modify a the outside of the egg and removed the binding location
What is syngamy and why is it considered by some to the beginning of life
The fusion of the protonuclei and the first cell division this is considered by some to be the unique development of the zygote
Why argue against syngamy for start of life
The DNa of the protonuclei stays very separate
When does organism function begin and so what
The function begins at the fusion of the sperm and this is considered the start of life by some
Describe in brief the first few days after conception
Syngamy in the zygote surrounded by the zona pellucida; cleavage, then divide to 32 cells to make the morula, then the cells form junctions and then compaction this leads to the formation of the embryoblasts and the tropoblasts that then seperate to form the ICM and the blastecoel. This is the blastocyst. This hatches from the Zona pallucida The ICM then forms the embryo and the tropoblasts form the placenta.
The intercell mass also forms and the embryonic stem cells
How does an MVR escape the confines of the zona pellucida?
Through a process called hatching where the embryo escapes the pellucida
What is the definition of a stem cell
Any cell that divides to generate one cell that replaces itself and one cell destined to become something new
Why is the generation of embryonic stem cells so controversy all
Because it effectively destroys the blastocyst in there by the fetus
How do we know that embryonic stem cells retain the ability to respond to embryonic environment and formcorrect tissue
Embryonic stem cells that have been removed from a embryo can be replaced into a morula stage embryo and they will participate in normal development
Generally speaking which blastomere will contribute to the intercell mass
The leading blastomere
Describe the process of implantation of the blastocyst
The trophoblast will derive the cytotrophoblast and the syncytiotrophoblast (that is the extention implanting into the cell) this will also produce hCG to sustain self. The ICM will form two layers: The epiblast next to the syncytiotrophoblast, and the hypoblast that faces the blastecoel. Then the amniotic cavity opens up under the epiblast and hauser’s membrane is formed from the hypoblast migrating to line the blastocyst cavity, this makes the yolk sack.
How does the embryonic cell know to form a trophoblast or to form part of the intercell mass
This differentiation is determined by two chemicals CD X2 and OCT 3/4. CD X2 will lead to the formation of trophoblast and OCT 3/4 will lead to the formation of intercell mass both of these chemicals up regulate themselves and down regulate the other
Why is there not a random distribution of CD X2 and OCT 3/4 expressing’s cells
Some kind of putative apical signal activator stabilizes CD X2 in the outer cells once the balance of shifted towards one of these chemicals all of the surrounding cells will be stabilized express the same chemical and therefore become trophoblast
What kind of malformation exists when there’s an excess or exclusive expression of CD X2 and therefore the formation of it excessive trophoblast
This is called a hydatidiform moles
Why would I levels of H CT vaginal bleeding and rapid expansion of the uterus be an indication for concern
This could indicate the presence of a hydatidiform mole
How is the formation of a hydatidiform mole related to the idea of diploidy sperm
A mole happens when you have a cell that has only paternal chromosomes due to the presence of extra Male pro nuclei. This can occur through two sperm or a diploid sperm
What are three common human imprinting disorders
Angleman syndrome Prater Willy syndrome and Beckwith Weidman syndrome. These are five times more likely than children conceived through IVF
What are some common abnormal implantation sites for an embryo
From the beginning of the fallopian tube towards the uterus common implant sides are fimbrial ampullary isthmus or even cervical there can even be sites outside the cervical in the gut
What is a stem Villus and how does it form
The capillary connection to the leaking supply of the mothers blood. And it forms from the extra embryonic mesoderm
Why is the mature placenta not a maternal Oregon
The only maternal cells that could be found in the placenta are blood cells that leak out of the maternal circulation into the placenta all of the other cells are fetal
What are three common functions of the placenta
Transport of oxygen and nutrients to the fetus and removal of waste number to synthesis and secretion of hormones for the maintenance of pregnancy and preparation of lactation. And number three modulation of the maternal immune system
What’s the difference between monozygotic and dizygotic twins
Monozygotic twins come from the same to sell stage zygotes they can have common placenta or even common amniotic cavity or separate placentas dizygotic twins will have separate placentas and come from two different zygotes
Where can the primordial germ cells be first detected
In the yolk sac wall
