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Foundations Week 8 > Gametogenesis & fertilization > Flashcards

Gametogenesis & fertilization Flashcards

0
Q

Failure to form viable gametes is a major cause of ___

A

infertility

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1
Q

What is gametogenesis?

A

process that produces egg cells in female & sperm cells in male

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2
Q

Defects in gametogenesis may lead to chromosome copy # abnormalities in the zygote which are a primary cause of ___ & ___

A

preimplantation & early embryonic death

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3
Q

What are the 2 periods of human development. How long do they last?

A

Embryonic period- fertilization to 8 weeks
- first 4 weeks are used to develop basic body plan of embryo & second 4 weeks for organ formation

Fetal period - subsequent 8 weeks
- growth. This produces final shape & size of new born & final shape & structure of organs

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4
Q

Meiosis produces cells with half of normal number of chromosomes, which is __ # of chromosomes

A

23

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5
Q

Germ cells contain __ copy(ies) of each chromosome.

A

1

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6
Q

When does oogenesis begin?

A

process of oogenesis begins before birth.

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7
Q

At birth, female contains about ___ (#) oocytes, but this number decreases to about ___ by puberty due to ____

A

2M; 50K; cell death

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8
Q

Oogenesis occurs ___ (Where). Every month about ___ primary oocytes undergo ___, each within a structure called the ___

A

in the ovary; 15-20; maturation;follicle

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9
Q

Oocytes are arrested in ___ meiosis prior to birth & only complete __ meiosis as they progress towards ____ (after ___)

A

1st; 1st; ovulation; puberty

they put aside 1 copy of DNA - inert

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10
Q

It is only during ___ that the 2nd meiotic division commences to generate the haploid cell. Second meiosis is completed ONLY when ovum has been ___.

A

ovulation; fertilized.

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11
Q

The complete process of oogenesis generates a single ovum plus __ (#) nonviable polar bodies, all with 22 + X chromosome complement.

A

3

In general, only 1 ovum is released during each cycle of ovulation

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12
Q

What are mature sperm cells called?

A

spermatozoa

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14
Q

The complete process of spermatogenesis generates ___ sperms cells, __ 22 + X & __ 22 + Y

A

4; 2; 2

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15
Q

Where does sperm development occur?

A

seminiferous tubules

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16
Q

Maturation of sperm occurs in organized fashion - precursor cells on outside, more ___ cells closer to lumen

A

differentiated

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17
Q

Infertility in men may be due to ___.

A

absence of mature sperm near the lumen of seminiferous tubules

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18
Q

Abnormal meiotic divisions can produce either __ or ___ chromosomes in an ovum/sperm

A

extra or missing

This will later result in variations in chromosome # in fertilized egg

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19
Q

The most commonly observed chromosomal abnormalities are ___

A

trisomies - 3 copies of a chromosome

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20
Q

____ of chromosome other than sex chromosomes is invariably lethal

A

loss

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21
Q

What is trisomy 21?

A

Down’s syndrome & occurs 1/1000 births - very common

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22
Q

Approximately 75% of concepti with trisomy 21 die in embryonic/fetal life. Of those born, approximately 85% survive to age 1 year & 50% can be expected to live to age ___ years/more.

A

50

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23
Q

What is FISH detection of trisomies?

A

cells may be collected from amniotic fluid surrounding fetus They can be assayed for correct chromosome #. especially 21, 18 & 13

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24
Q

What is trisomy 13?

A

Pateau’s syndrome - involves multiple abnormalities, many of which aren’t compatible with life. 50% of infants die after 1st week. More than 80% of children with trisomy 13 die in 1st month. Some live to their teens
observed in about 1/5000

25
Q

What is Turner’s syndrome?

A

females inherit single X chromosome - XO
1/3000
variation in sex chromosomes is fairly common
fairly extensive medical issues - short stature, webbed neck reduction in secondary female characteristics, ovaries don’t develop –> sterility

26
Q

What is Klinefelter syndrome?

A

extra copy of X in males - XXY
1/700
1 copy of X is inactivated
No major medical problems though they may possess some feminine characteristics - higher voice, breast enlargement reduced body hair

thought to be significantly under diagnosed

27
Q

What is Robertsonian translocation?

A

chromosomal rearrangement

translocation between ch13 & ch14 is by far most common

28
Q

What is spermatogenesis?

A

Beginning at puberty, germ cells in male undergo standard meiotic division to produce 4 spermatids which later become mature sperm cells - spermatozoa

29
Q

What is fertilization?

A

involves successful fusion of male & female gamete cells

Normally occurs in ampullary region of uterine tube (ampulla means flask/bottle); quite close to ovaries

30
Q

What is capacitation?

A

removal of GP surrounding sperm when in female reproductive tract

Within female reproductive tract, prior to encountering the ovum, GP surrounding the sperm are removed. Removal of GP is necessary for fertilization to occur

31
Q

Sperm must penetrate through what layers to enter the ovum?

A

outer - corona radiata/cumulus oophorus

inner GP layer - zona pellucida

32
Q

The ability to penetrate the layers of the ovum by the sperm is controlled by ____ enzymes released from tip of sperm

A

acrosomal

33
Q

What is the next step after sperm reaches the egg membrane?

A

Fusion of sperm membrane with oocyte membrane. Fusion event enables sperm head & tail to enter ovum

34
Q

When is the second meiotic division of ovum completed?

A

when sperm & egg fuse. Now one set of maternal chromosomes is expelled in 2nd polar body

35
Q

What is a mechanism to prevent polyspermy?

A

fast block - change in membrane potential that prevents further sperm fusion events

slow block - at time of sperm entry, ovum undergoes event called cortical reaction. This forms a space between egg membrane & zona pellucida - perivitelline space

Digestive enzymes are releasedd into perivitelline space

36
Q

At time of sperm entry, ovum undergoes event called ____. This forms a space between egg membrane & zona pellucida = _______

___ enzymes are released into ____ space

A

cortical reaction; perivitelline; digestive; perivitelline

37
Q

After entering ovum of tail of sperm degenerates & head enlarges/decondenses to form male ___

A

pronucleus

Male & female pronuclei fuse to form single diploid nucleus

fertilized egg –> zygote

38
Q

After fertilization, cell division __. Division occurs about every ___ hours

A

commenses; 16-24 hrs

39
Q

The early mitotic division take place without cell growth (reductional division) leading to larger # of ___ cells. Zygotic cells will contribute to __ or ___ tissues

A

smaller; embryo or extraembryonic tissues

40
Q

The 8-16 cell stage is called the ___

A

morula stage.

During early cell divisions (2-cell to 16-cell) all cells are equivalent. Initially they are loosely associated with each other but then they become compacted

41
Q

Between the 32 & 128 cell stages, the morula begins to organize into a ___/___ around a central cavity called the ___/__ cavity.

A

blastula/blastocyst

blastocele/blastocyst activity

42
Q

As cell division continues, embryo moves along uterine tube to uterus (driven by ciliary motion). At about 5-6 at blastocyst stage, the embryo will ___

A

implant

43
Q

What causes infertility?

A

inflammation/tissue damage in uterine tube can prevent access of sperm to egg or movement of zygote into uterus

Defects in ciliary action prevent movement of zygote towards uterus & are major genetic cause of infertility

44
Q

What is ectopic pregnancy?

A

when zygote implants in tissue other than uterine wall. This most often occurs in wall of uterine tuber (~95%). The embryo usually dies after about 30 days but this may be associated with severe hemorrhaging which can threaten life of mother

45
Q

It is estimated that almost ___ of all zyogtes fail to implant

A

1//2;

Even after successful implantation another 20-25%are lost to spontaneous abortion.

46
Q

What is a major cause of spontaneously terminated embryos?

A

congenital abnormalities - ex - heart defects

47
Q

What is a trophoblast? Most of trophoblast will form the ___ which is a population of cells with 1 nucleus each

A

cells comprising outer cell layer of blastocyst will form trophoblast

cytotrophoblast

48
Q

Trophoblast cells close to inner cell mass will form the ___ population. These are multinucleated, highly invasive cells. Retroviral-derived protein, __ is essential for formation of ___ tissue

A

syncytiotrophoblast; syncytin; syncytiotrophoblast

49
Q

Attachment of synctiotrophoblast cells to uterine wall begins ___. Initial attachment is mediated by ___ on cell surafce of synctiotrophoblast cells adhering to ___ on endometrium of uterus

A

implantation; L-selectin; oligosaccharides

50
Q

After attachment, syncytiotrophoblast cells invade the endometrium of uterus & eventually cover the ___ layer

A

cytotrophoblast layer

51
Q

The syncytiotrophoblast cells digest their way into endometrium of uterus & wrap themselves around ___ during invasion

A

cytotrophoblast

52
Q

What are fraternal/dizygotic twins?

A

separate ovulation, fertilizations & implantations

Fraternal twins have genetic component no more alike than any 2 siblings

2/3 of twins

53
Q

What are monozygotic/identical twins

A

1/3. Splitting of embryo during early cleavage stages (before 8 cells) or formation of 2 inner cell masses

54
Q

What are identical triplets?

A

6% of triplet births

more common are triplets with 1pair of identical twins & 1 independent

55
Q

Identical twins in same chorion can sometimes ____

A

fuse to be conjoined

1/200 identical twin births

56
Q

Twins who are born premature is __

A

common

57
Q

__ pregnancy is the largest single cause of multiple births

A

assisted

multiple births are largest single cause o prematurity

58
Q

what are serious health consequences of premature birth?

A

incomplete brain development
respiratory problems
vision, hearing
jaundice (elevated bilirubin levels)

Foundations Week 8 (8 decks)

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