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4 RED > 6 Fertilisation > Flashcards

6 Fertilisation Flashcards

1
Q

What picks up the cumulus-oocyte?

A

ciliated fimbriae on infundibulum

aided by chemoattraction (follicular fluid) and muscular contractions

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2
Q

How quickly do sperm coagulate?

A

1 minute

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3
Q

What facilitates sperm coagulation?

A

enzymes act on semenogelin

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4
Q

What facilitates flowback of sperm?

A

PSA action on semenogelin

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5
Q

What percentage of sperm deposited will be lost due to gravity?

A

95%

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6
Q

When is cervical mucous least viscous?

A

days 9-16 of the menstrual cycle

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7
Q

How long do sperm remain in the female tract?

A

5 days

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8
Q

How long does the oocyte remain viable?

A

24 hours

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9
Q

What do ovulation prediction kits detect?

A

LH surge

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10
Q

What are the 5 states of sperm interaction with egg vestments?

A 
remote detection of oocyte-cumulus complex
penetration of cumulus
zona binding
acrosome reaction
zona penetration
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11
Q

What is the cumulus?

A

3000 cells embedded in gelatinous matrix w/ hyaluronic acid

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12
Q

How can sperm penetrate the cumulus?

A

carry hyaluronidase

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13
Q

Why is the acrosomal reaction important?

A

it exposes the new membrane for oocyte fusion

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14
Q

What is the zona pelllucida made of?

A

4 glycoproteins

ZP1, ZP2, ZP3, ZP4

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15
Q

What happens to the zona pellucida post-fertilisation?

A

embryo will hatch to reveal trophoblast cells which interact with the endometrium

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16
Q

Where does the sperm reside immediately after penetrating the ZP?

A

pereviteline space

between ZP and PM

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17
Q

What part of the sperm fuses with the oocyte PM?

A

equatorial segment of sperm head

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18
Q

What increases in fusion?

How quickly does this occur?

A

Ca2+
sweeps across egg from point of sperm fusion

1-3 mins
then oscillations every 3-15 mins

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19
Q

What is the sperm membrane receptor for fusion called?

A

izumo

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20
Q

when is the sperm membrane receptor for fusion detectable?

A

after acrosomal reaction

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21
Q

What is the oocyte membrane receptor for fusion called?

A

Juno

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22
Q

What triggers increased calcium levels post-fusion?

A

PLC zeta in sperm

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23
Q

What is MPF?

A

M-phase Promoting factor

cdk1 + cyclin B

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24
Q

What does MPF do?

A

blocks metaphase to anaphase transition

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25
Q

What does CSF do?

A

Cytostatic factor

stabilises MPF

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26
Q

What happens to CSF post-fertilisation?

A

suppressed by raised Ca2+

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27
Q

What happens to cyclin B post-fertilisatoin?

A

destroyed by activating anaphase-promoting complex

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28
Q

What do cohesion protein complexes do?

A

ring like strucutres holding sister chromatids together

29
Q

What does separase no?

A

cleaves Scc1 subunit of cohesion complexes

30
Q

What does securin do?

A

inhibits separase activity until ubiquinated by APC/C

31
Q

What is involved in the fast block to polyspermy?

A

membrane depolarisation

32
Q

What is involved in the slow block to polyspermy?

A

cortical reaction triggered by Ca2+

33
Q

What happens in the cortical reaction?

A

cortical granules diffuse into ZP following exocytosis

induces the zona reaction

34
Q

What is the zona reaction?

A

alteration in ZP structure post fertilisation catalysed by protease from cortical granules

35
Q

What facilitates the zona reaction?

A

ovastacin protease cleaves ZP2

36
Q

What happens to Juno to block polyspermy?

A

it is shed from the PM so sperm can’t fuse

37
Q

What do sperm contribute to the zygote?

A

haploid genes - sex of baby

centriole

38
Q

What does the oocyte contribute to the zygote?

A

haploid genome
cytoplasm
all organelles
mitchondria

39
Q

What happens in the zygotic / pronucleate stage?

A

decondensation of sperm DNA (protamine/histone exchange)
DNA replication
pronuclei migrate towards each other

40
Q

What structure allows pronuclei to migrate towards each other?

A

sperm aster from centrosomes

41
Q

What is syngamy?

A

the combination of male and female pronuclei

42
Q

How long does it take for syngamy to occur?

A

18-24 hours

43
Q

What else happens in syngamy?

A

pronuclei membranes break down
chromatin mixes
new nucelar envelope forms
cleavage begins (marks beginning of embryogenesis)

44
Q

What facilitates the transport of embryo to the uterus?

A

increased pogesterone : oestrogen ratio
relaxes muscules at isthmic sphincter and UTJ
cilia action

45
Q

What does the zygote cleave to form?

A

2 blastomeres

46
Q

What is the 16-32 cell stage called?

A

morular

47
Q

Where would you find the morular?

A

near the end of the uterine tube

48
Q

Why does blastomere size decrease with each division?

A

no cytoplasmic synthesis

49
Q

What happens from the 8 cell stage onwards?

A

inside-outside polarity develops

50
Q

What are the outer cells of the embryo?

A

trophoblasts

placenta

51
Q

What are the inner cells of the embryo?

A

inner cell mass

embryoblast

52
Q

What is a late morula?

A

fluid filled cavity formed by fluid absorption

53
Q

What maintains the structure of the late morula?

A

intercellular junctions between trophoblasts

Na+/K+ ATPase pumps Na+ into cavity to draw in water

54
Q

What is the blastocyst fluid-filled cavity called?

A

blastocoel

55
Q

What does the trophoblast layer secrete, what does this do?

A

secretes hCG

maintians corpus luteum

56
Q

What are the embryonic poles?

A

embryonic pole

abembryonic pole

57
Q

What is hatching and when does it occur?

A

blastocyst expands out of hole in ZP and squeezes out via abembryonic pole for implantation

day 6 onwards

58
Q

Name 2 factors increasing the risk of dizygotic twins

A

maternal age

fertility treatment

59
Q

Name a factor increasing the risk of monozygotic twins

A

in vitro embryonic culture

60
Q

What might happen as a result of monochorionic twins?

A

twin-twin transfusion syndrome

imabalnce of blood flow

61
Q

What might having twins cause for the mother?

A

PRE
HTN
GD
mortality

62
Q

What problems might arise for a baby as a twin?

A

premature birth
LBW
cerebral palsy

63
Q

What stimulates endometrial proliferation?

A

oestrogen

64
Q

What stimulates synthesis of secretory material by endometrial glands?

A

progesterone released by ovaries

65
Q

What happes to the endometrium as a result of progesterone release?

A

stromal cells become bigger
spiral arteries become fully developed
cellular secretions released into glandular epithelium (must be oestrogen-primed)

66
Q

When is the window of implantation?

A

Days 20-24

67
Q

What forms in the endometrium during the window of implantation?

A

small elevations in the apical pole of epithelial endometrium cells (pinopodes)

68
Q

What are pinopodes?

A

involved in absorption of uterine fluid
bring blastocyst closer to endometrium
immobilise it for implantation

69
Q

How does menstruation occur?

A

spiral arteries constrict when progesterone falls
collapse and necrosis of functional layer
blood and necrotic tissue is lost

4 RED (15 decks)

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