L1: Initiation of pregnancy Flashcards by Ellen Moore

2 functions of the female reproductive tract

supports gametes

supports pregnancy

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2 phases of the female cycle

luteal phase

follicular phase

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what dominates the luteal phase

corpus luteum

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how long can sperm survive in the female reproductive tract

5 days

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how long can an egg survive

24hrs

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where is the site of fertilisation

ampullary isthmic junction

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what helps the sperm reach its goal

uterine/ oviduct contractions

beating of cilia in fallopian tubes

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how many sperm are lost to leakage

99%

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

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

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what can freshly ejaculated sperm not do

fertilise eggs

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what is required for sperm to fertilise eggs

capacitation

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what do sperm need time away from to undergo capacitation

seminal plasma/ epididymal fluid

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2 process of capacitation

hyperactivation

removal of acrosome

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what drives the 2 processes of capacitation

calcium

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what is hyperactivation

when sperm start swimming

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what allows removal of the acrosome

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

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

cumulus cells

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

hyaluronidase (from the acrosome)

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where is hyaluronidase enzyme released from

acrosome

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second barrier of egg to sperm

zona pellucida

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what enzyme allows sperm to bind to the zona pellucida

acrosin

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

Gp ZP2/3

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what triggers the acrosome reaction to digest zona pellucida

close proximity to the oocyte

- binding to ZP2/3

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how long does it take sperm to penetrate the zona pellucida

5-20 minutes

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after penetration of the zona pellucida where do the sperm sit

intermembrane gap between zona pellucida and oocyte membrane

what happens to the sperm in fusion

sperm binds to oocyte membrane and is engulfed into oocyte cytoplasm

what happens to the egg once the sperm has entered

egg becomes activated

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

metaphase 2

2 things sperm contributes

DNA | phospholipase C gamma

what is phospholipase C gammas role

starts cascade to elevate calcium

in egg activation how often in calcium released

in 10 minute spikes

what cause the arrested oocyte to move out of metaphase 2

calcium elevations

what does calcium do to enable the oocyte to initiate meiosis

calcium breaks down MPF

what is MPF responsible for

maintaining oocyte arrest

what is the second meiotic division like

unequal forming a polar body

why is a polar body formed

to get rid of chromosomes

what is the best indication fertilisation has occurred

presence of the polar body

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

zygote

what prevents polyspermy

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

polyspermic egg=

multiple sperm more than 2 pronuclei | embryo won't develop past 4 cells

dygynic fertilisation

error in meiosis causing multiple female pronuclei

pathogenic activation

egg activated without male pronucleus

how many cells after 24 hours

4 cell embryo

how many cells after 48 hours

8 cell embryo

how many days for blastocyst to form

5-6

what is the first thing to happen in cleavage

rewriting the genome

what is rewriting the genome

DNA embryo wiped of all epigenetics marks | all DNA is demethylated and remethylated

when does rewriting the genome happen

4-8 cell point

5 first developmental milestones

zygote cleavage morula blastocyst

what happens at the morula stage

cell- cell junctions form

5 things that happen in the blastocyst

``` differentiation protein synthesis Na+/K+/ATPase true growth prep for implantation ```

when in the point of initiation of pregnancy

blastocyst

how does the blastocyst implant

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

what can the female reproductive tract check the embryo for

its quality (and reject poor quality)

what does the blastocyst signal to be maintained

corpus luteum

what does corpus luteum continue to release

progesterone

what hormones are essential to sustain embryo in early stages

human chorionic gonadotropin (hCG) | progesterone

when is the corpus luteum no longer needed

after 1st trimester

where is hCG released from

syncytiotrophoblasts - 2wks post fertilisation

what does hCG act on

LH receptors on corpus luteum to increase progesterone output

what test can hCG be used for

pregnancy test

by 6wks what maintains pregnancy

coceptus progesterone and pregnenolone

what do the fetus and placenta work together to produce

oestrogens

fetal adrenal synthesises _______

C19 androgens

what does the placenta do to C19 androgens

aromatizes them to oestrogen's

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

corpus luteum

2 forms of twins

monozygotic twins | dizygotic twins

5 forms of monozygotic twins

``` early embryo splitting fused dichorionic ICM split embryonic disc split incomplete split ```

most common monozygotic twins

early embryonic splitting

what membrane do fused dichorionic twins share

chorionic membrane (own amion membrane)

what can form conjoined twins

incomplete split

what causes dizygotic twins

double ovulation

2 assisted fertilisations

IVF | ICSI

ICSI=

intracytoplasmic sperm injection

4 parts of IVF

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

what was a key breakthrough in IVF

superovulation by a series of hormonal treatments before

assisted fertilisation success rates

25%

what enzyme dominates the follicular phase

oestrogen

what causes LH sudden boost

critical oestrogen concentration

which stage of the female cycle is a constant length

luteal phase (14 days)

what feedback does oestrogen normally cause of LH

negative feedback

what does LH surge cause

follicle rupture

hormone dominating luteal phase

progesterone

what happens without progesterone

endometrial lining shed

L1: Initiation of pregnancy Flashcards

(84 cards)