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Block 11: Ellen > L1: Initiation of pregnancy > Flashcards

L1: Initiation of pregnancy Flashcards

1
Q

2 functions of the female reproductive tract

A

supports gametes

supports pregnancy

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2
Q

2 phases of the female cycle

A

luteal phase

follicular phase

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3
Q

what dominates the luteal phase

A

corpus luteum

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4
Q

how long can sperm survive in the female reproductive tract

A

5 days

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5
Q

how long can an egg survive

A

24hrs

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6
Q

where is the site of fertilisation

A

ampullary isthmic junction

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7
Q

what helps the sperm reach its goal

A

uterine/ oviduct contractions

beating of cilia in fallopian tubes

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8
Q

how many sperm are lost to leakage

A

99%

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9
Q

what happens to the 1% of sperm that make it to the oviduct

A

bind to the oviduct epithelia and rest forming a functional sperm reservoir

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10
Q

what can freshly ejaculated sperm not do

A

fertilise eggs

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11
Q

what is required for sperm to fertilise eggs

A

capacitation

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12
Q

what do sperm need time away from to undergo capacitation

A

seminal plasma/ epididymal fluid

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13
Q

2 process of capacitation

A

hyperactivation

removal of acrosome

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14
Q

what drives the 2 processes of capacitation

A

calcium

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15
Q

what is hyperactivation

A

when sperm start swimming

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16
Q

what allows removal of the acrosome

A

pH/ temperature changes in the reproductive tract change the composition of the acrosome membrane allowing calcium to enter

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17
Q

what is the first barrier of the egg for sperm to get through

A

cumulus cells

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18
Q

how do sperm get through the hyaluronic acid of the ECM of the cumulus cells

A

hyaluronidase (from the acrosome)

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19
Q

where is hyaluronidase enzyme released from

A

acrosome

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20
Q

second barrier of egg to sperm

A

zona pellucida

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21
Q

what enzyme allows sperm to bind to the zona pellucida

A

acrosin

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22
Q

what does acrosin facilitate sperm to bind to on the zona pellucida

A

Gp ZP2/3

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23
Q

what triggers the acrosome reaction to digest zona pellucida

A
  • close proximity to the oocyte

- binding to ZP2/3

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24
Q

how long does it take sperm to penetrate the zona pellucida

A

5-20 minutes

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25
Q

after penetration of the zona pellucida where do the sperm sit

A

intermembrane gap between zona pellucida and oocyte membrane

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26
Q

what happens to the sperm in fusion

A

sperm binds to oocyte membrane and is engulfed into oocyte cytoplasm

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27
Q

what happens to the egg once the sperm has entered

A

egg becomes activated

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28
Q

what stage of division is the oocyte arrested in before sperm entry

A

metaphase 2

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29
Q

2 things sperm contributes

A

DNA

phospholipase C gamma

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30
Q

what is phospholipase C gammas role

A

starts cascade to elevate calcium

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31
Q

in egg activation how often in calcium released

A

in 10 minute spikes

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32
Q

what cause the arrested oocyte to move out of metaphase 2

A

calcium elevations

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33
Q

what does calcium do to enable the oocyte to initiate meiosis

A

calcium breaks down MPF

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34
Q

what is MPF responsible for

A

maintaining oocyte arrest

35
Q

what is the second meiotic division like

A

unequal forming a polar body

36
Q

why is a polar body formed

A

to get rid of chromosomes

37
Q

what is the best indication fertilisation has occurred

A

presence of the polar body

38
Q

what is it called when the female and male pronucleus come together

A

zygote

39
Q

what prevents polyspermy

A

egg calcium rise causes the release of cortical granules which degrade ZP2/3

40
Q

polyspermic egg=

A

multiple sperm more than 2 pronuclei

embryo won’t develop past 4 cells

41
Q

dygynic fertilisation

A

error in meiosis causing multiple female pronuclei

42
Q

pathogenic activation

A

egg activated without male pronucleus

43
Q

how many cells after 24 hours

A

4 cell embryo

44
Q

how many cells after 48 hours

A

8 cell embryo

45
Q

how many days for blastocyst to form

A

5-6

46
Q

what is the first thing to happen in cleavage

A

rewriting the genome

47
Q

what is rewriting the genome

A

DNA embryo wiped of all epigenetics marks

all DNA is demethylated and remethylated

48
Q

when does rewriting the genome happen

A

4-8 cell point

49
Q

5 first developmental milestones

A

zygote
cleavage
morula
blastocyst

50
Q

what happens at the morula stage

A

cell- cell junctions form

51
Q

5 things that happen in the blastocyst

A 
differentiation 
protein synthesis 
Na+/K+/ATPase 
true growth 
prep for implantation
52
Q

when in the point of initiation of pregnancy

A

blastocyst

53
Q

how does the blastocyst implant

A

it releases a compound leading to signalling cascade in the uterus epithelium causing a rise in heparin binding EGF and the EGF receptor remodels integrins into the epithelium of the female reproductive tract allowing the blastocyst to bind and become enveloped

54
Q

what can the female reproductive tract check the embryo for

A

its quality (and reject poor quality)

55
Q

what does the blastocyst signal to be maintained

A

corpus luteum

56
Q

what does corpus luteum continue to release

A

progesterone

57
Q

what hormones are essential to sustain embryo in early stages

A

human chorionic gonadotropin (hCG)

progesterone

58
Q

when is the corpus luteum no longer needed

A

after 1st trimester

59
Q

where is hCG released from

A

syncytiotrophoblasts - 2wks post fertilisation

60
Q

what does hCG act on

A

LH receptors on corpus luteum to increase progesterone output

61
Q

what test can hCG be used for

A

pregnancy test

62
Q

by 6wks what maintains pregnancy

A

coceptus progesterone and pregnenolone

63
Q

what do the fetus and placenta work together to produce

A

oestrogens

64
Q

fetal adrenal synthesises _______

A

C19 androgens

65
Q

what does the placenta do to C19 androgens

A

aromatizes them to oestrogen’s

66
Q

what is no longer required once steroid synthesis beings (foetal placental unit)

A

corpus luteum

67
Q

2 forms of twins

A

monozygotic twins

dizygotic twins

68
Q

5 forms of monozygotic twins

A 
early embryo splitting 
fused dichorionic 
ICM split 
embryonic disc split 
incomplete split
69
Q

most common monozygotic twins

A

early embryonic splitting

70
Q

what membrane do fused dichorionic twins share

A

chorionic membrane (own amion membrane)

71
Q

what can form conjoined twins

A

incomplete split

72
Q

what causes dizygotic twins

A

double ovulation

73
Q

2 assisted fertilisations

A

IVF

ICSI

74
Q

ICSI=

A

intracytoplasmic sperm injection

75
Q

4 parts of IVF

A

eggs collected from superovulated ovary
eggs aspirated in tube and placed in dish
fertilisation in dish
transfered back to uterus at 4 cell stage or blastocyst

76
Q

what was a key breakthrough in IVF

A

superovulation by a series of hormonal treatments before

77
Q

assisted fertilisation success rates

A

25%

78
Q

what enzyme dominates the follicular phase

A

oestrogen

79
Q

what causes LH sudden boost

A

critical oestrogen concentration

80
Q

which stage of the female cycle is a constant length

A

luteal phase (14 days)

81
Q

what feedback does oestrogen normally cause of LH

A

negative feedback

82
Q

what does LH surge cause

A

follicle rupture

83
Q

hormone dominating luteal phase

A

progesterone

84
Q

what happens without progesterone

A

endometrial lining shed

Block 11: Ellen (7 decks)

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