8/18 Embryo Foundations

Question 1

How are the primordial germ cells unique as compared to other cells

Answer 1

The are unilique in their motility and their potency or ability to create all different types of cells

Question 2

How does the migratory destination of a primordial germ cells affect third unique properties.

Answer 2

The final location in the genital ridge will suppress he motility and he potency of the cells…otherwise they develop horrible tutors

Question 3

What is meiotic reduction

Answer 3

The reduction height he first meiotic division of the chromosome number to 23 from 46 thus creating haploid a

Question 4

What are the main goals of gametogenesis?

Answer 4

Meotic reduction
Recombination
Morphological dofferentiation of gametes to prep for fertilization
Cytoplasmic localization of materials to prep for development

Question 5

What is the major morphological change that results in many I the common abnormalities such as Down syndrome

Answer 5

Nondisjunction

Question 6

Describe Nondisjunction

Answer 6

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

Question 7

What is the result of Nondisjunction

Answer 7

Aneuplioidy 
Down's syndrome 21*3
Turners syndrome monosomy of the x
Klinefelters xxy
Patau syndrome trisomy 13
Edwards syndrome trisomy 18

Question 8

what hormone causes the differentiation of the pgc

Answer 8

tstoserone

Question 9

why is the spermatids considered syncytia?

Answer 9

they develop as a gropu where they share the same cytoplasm therefore nucleus is plural in a shared cytoplasm.

Question 10

why lmight a reason be for te increaseinthe occurance of autism in the last few decaces

Answer 10

the incdreasing age of fahers as fathers age they have a higher riskof abnormal sperm and geetic abnormalities

Question 11

what happans when the pgc in a female reach the genital cleft or the gonads

Answer 11

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.

Question 12

described the female menstral cycle

Answer 12

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

Question 13

When would a second meiotic division take place in the eggs?

Answer 13

Only following fertilization

Question 14

What is the corpus lotum

Answer 14

The ring of folicle cells that surround the oocyte

Question 15

The oocyte has all that is needed for cell differentiation and control how do we know this

Answer 15

Because cloning worked with dilly the sheep

Question 16

What are some of the regulatory goals of fertilization

Answer 16

Same species
No polyspermy
Robust sperm fertilize
Activate the egg
Restore the diploid state

Question 17

How ensure same species fertilize

Answer 17

Behavior and biogival such as capacitation or loss o the cholesterol head in genital tract

Question 18

Name three phases of fertilization

Answer 18

Penetration of the cumulus oophorus

Adhesion to and digestion of zona pellucida and the fusion of the egg and the sperm plasma membrane

Question 19

How does the egg prevent polyspermy?

Answer 19

Cortical reaction of the egg that modify a the outside of the egg and removed the binding location

Question 20

What is syngamy and why is it considered by some to the beginning of life

Answer 20

The fusion of the protonuclei and the first cell division this is considered by some to be the unique development of the zygote

Question 21

Why argue against syngamy for start of life

Answer 21

The DNa of the protonuclei stays very separate

Question 22

When does organism function begin and so what

Answer 22

The function begins at the fusion of the sperm and this is considered the start of life by some

Question 23

Describe in brief the first few days after conception

Answer 23

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

Question 24

How does an MVR escape the confines of the zona pellucida?

Answer 24

Through a process called hatching where the embryo escapes the pellucida

Question 25

What is the definition of a stem cell

Answer 25

Any cell that divides to generate one cell that replaces itself and one cell destined to become something new

Question 26

Why is the generation of embryonic stem cells so controversy all

Answer 26

Because it effectively destroys the blastocyst in there by the fetus

Question 27

How do we know that embryonic stem cells retain the ability to respond to embryonic environment and formcorrect tissue

Answer 27

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

Question 28

Generally speaking which blastomere will contribute to the intercell mass

Answer 28

The leading blastomere

Question 29

Describe the process of implantation of the blastocyst

Answer 29

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.

Question 30

How does the embryonic cell know to form a trophoblast or to form part of the intercell mass

Answer 30

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

Question 31

Why is there not a random distribution of CD X2 and OCT 3/4 expressing’s cells

Answer 31

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

Question 32

What kind of malformation exists when there’s an excess or exclusive expression of CD X2 and therefore the formation of it excessive trophoblast

Answer 32

This is called a hydatidiform moles

Question 33

Why would I levels of H CT vaginal bleeding and rapid expansion of the uterus be an indication for concern

Answer 33

This could indicate the presence of a hydatidiform mole

Question 34

How is the formation of a hydatidiform mole related to the idea of diploidy sperm

Answer 34

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

Question 35

What are three common human imprinting disorders

Answer 35

Angleman syndrome Prater Willy syndrome and Beckwith Weidman syndrome. These are five times more likely than children conceived through IVF

Question 36

What are some common abnormal implantation sites for an embryo

Answer 36

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

Question 37

What is a stem Villus and how does it form

Answer 37

The capillary connection to the leaking supply of the mothers blood. And it forms from the extra embryonic mesoderm

Question 38

Why is the mature placenta not a maternal Oregon

Answer 38

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

Question 39

What are three common functions of the placenta

Answer 39

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

Question 40

What’s the difference between monozygotic and dizygotic twins

Answer 40

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

Question 41

Where can the primordial germ cells be first detected

Answer 41

In the yolk sac wall