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MSc - embryo exam > implantation and development > Flashcards

implantation and development Flashcards

1
Q

what happens on day 1 after fertilisation?

A

first cleavage

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2
Q

what happens on day 2 after fertilisation?

A

2 cell stage

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3
Q

what happens on days 3-4?

A

4 cell stage to an 8 cell uncompacted morula

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4
Q

what happens on day 4

A

8 cell compacted morula

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5
Q

what happens on day 5?

A

early blastocyst - (trophectroderm, blastocoel, inner cell mass)

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6
Q

what happens on day 6-7?

A

late stage blastocyst (hatching)

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7
Q

what happens day 8-9?

A

implantation of the blastocyst

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8
Q

what is transfer of the conceptus through the oviduct facilitated by?

A

changing endocrine milieu of the early luteal phase with its rising ratio of progesterone to oestrogen, which effects the oviducal and uterine musculature and relaxes the isthmus sphincter.

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9
Q

does the size of the conceptus change as blastomeres are undergoing devisions?

A

no the total size of the conceptus stays the same.

as a consequence the size of individual blastomeres is reduced progressively.

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10
Q

what happens when the conceptus reaches the maternal endometrium?

A

attachment and implantation

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11
Q

what is in the structure of a human blastocyst

A

zona pellucida
blastoceal cavity
inner cell mass

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12
Q

when is pregnancy initiated?

A

when the conceptus has signalled its presence successfully to the mother.

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13
Q

in the first 14-16 days of human development what are the two cell types types and what do they give rise to?

A

pluripotent embryonic cells - will give rise to a fetus
they are set apart and enveloped within various extra embryonic cells that will give rise to the supporting structures (mainly the placenta)

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14
Q

when and what is the embryogenic phase of development?

A

up to day 14

it is the generation of an embryo.

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15
Q

how long does the embryonic phase last for?

A

6 weeks

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16
Q

what happens during the embryonic phase?

A

various embryonic cells and tissue types differentiate and the basic body plan is laid down such that eventually tiny foetus formed.

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17
Q

what marks the end of the first trimester?

A

the transition from embryo to foetus

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18
Q

what are the essential factors for embryo implantation?

A

the implantation window (receptive endometrium)
healthy embryo at the blastocyst stage
communication between mother and the baby at the time of implantation.

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19
Q

what are the features of a receptive endometrium?

A

shortening of microvilli
loss of surface negative charge
thinning of the mucin coat
formation of pinopodes

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20
Q

what are the features of a non receptive endometrium

A

long apical microvilli
high surface negative charge
thick mucin layer

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21
Q

what is decidualization?

A

post ovulatory process of endometrial remodelling in preparation for pregnancy, which includes secretory transformation of the uterine glands, influx of specialised uterine natural killer cells and vascular remodelling.

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22
Q

what do decidualizing stromal cells acquire the ability to do?

A
  • regulate trophoblast invasion
  • resist inflammatory and oxidative insults
  • dampen maternal immune responses
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23
Q

in humans when does decidualization of stromal cells occur?

A

mid luteal phase of the menstrual cycle

independently of pregnancy

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24
Q

what hormone drives decidualization?

A

progesterone

it drives changes at both transcriptome and proteomic level

25
Q

when does compaction of the conceptus occur?

A

around the 8 to 16 cell stage

26
Q

what does the process of compaction involve?

A

maximising intercellular contacts and also the transformation of the cell phenotype from radially symmetrical to highly polarised or epithelioid.

27
Q

what two cell types does the blastocyst contain?

A

trophoblast cells

inner mast cells

28
Q

what is the first extra-embronic tissue made up of?

A

trophoblast cells

the do not contribute to the embryo of foetus

29
Q

what is the chorion and what is it derived from?

A

it is an accessory foetal membrane which is concerned with the nutrition and support of the embryo and foetus
it is derived from trophoblast cells

30
Q

what are the two function of the zona pellucida?

A
  • prevents the blastomeres of the conceptus form falling apart during earl cleavage, before compaction.
  • prevents two genetically distinct conceptus from sticking together to make a single chimeric conceptus composed of two sets of cells each of distinct genotype.
31
Q

where does the blastocyst that has not yet implanted get its oxygen and metabolic subtrees required for growth and survival from?

A

the uterine secretions that it is bathed in

32
Q

what are the 3 stages of implantation in humans?

A

apposition
attachment/adhesion
invasion

33
Q

what are short range signals

A

oocyte, sperm, seminal plasma and embryo

34
Q

what are long range signals?

A

hormones, nutrition and environmental factors

35
Q

in humans where does the blastocyst usually implant?

A

posterior wall of the uterine fundus

36
Q

what happen during adherence in implantation?

A

trophoblast cells of the blastocyst adhere to the luminal epithelial cells of the endometrium.

37
Q

what has to happens before adhesion can occur?

A

the zona pellucida has to be removed.

38
Q

where do the enzymes required for the removal of the zona pellucida come from?

A

trophoblast cells themselves or the uterine secretions

39
Q

what does attachment induce changes in?

A

endometrial epithelium and the underlying endometrial stromal tissue
(initiating its development as the maternal component of the placenta)

40
Q

different species have different types of implantation.

what are they two types of implantation?

A

invasive and non invasive

41
Q

which species does invasive implantation occur in?

A

humans, primates, dogs, cats, mice and rabbits.

the free living blastocyst of the species is relatively short lived

42
Q

which species does non invasive implantation occur in?

A

pig, sheep, cow and horse

attachment is initiated later than in invasive conception.

43
Q

when is hCG synthesised in the the trophoblast of the impacting blastocyst?

A

as early as 6-7 days after fertilisation.

44
Q

what is the role of pinipodes?

A

the may act to absorb uterine fluid to reduce the volume of the uterine cavity and so bring into close apposition the opposing epithelium (occlusion)

45
Q

when does the receptive phase occur?

A

day 7 to 10 of menstrual cycle

46
Q

when is the endometrium said to be prereceptive?

A

days 1 to 7 of menstrual cycle

47
Q

which hormone domination is required if the uterus and implanting blastocyst are to engage effectively?

A

progesterone

48
Q

what are the molecular messages of attachment?

A
  • firstly - go away messages from the luminal epithelium are switched off in order to remove barriers to attachment and adhesion.
  • then come hither messages are sent to promote active engagement of the conceptus.
49
Q

what is one of the key ‘go away’ messages provided by?

A

a glycoproteins called Muc1

50
Q

what is one of the key ‘come hither’ messages in attachment?

A

leukaemia inhibitory factor (LIF) –> a cytokine produced by the cells of the endometrial glands

51
Q

what does LIF do?

A

it permits the cells of the luminal epithelium to respond to local signals from activated blastocysts.
(sensitises the epithelium to the blastocyst)

52
Q

what are molecular messages of invasion?

A

MMPs - metalloproteinases - digest stomal components

TIMPs - tissue inhibitors of MMPs - holds MMPs in check.

53
Q

why is decidualization response by stomal cells at implantation described as resembling a pro inflammatory endometrial reaction?

A

because prostaglandins which are key players in inflammatory responses are involved in implantation.

54
Q

what are some molecular messages of invasion other than MMps and TIMPs.

A

prostaglandins
COX 2
vascular endothelial growth factor (VEGF)
interleukin 11

55
Q

how long does the fetal phase last for

A

220 days

56
Q

what does oestrogen stimulate proliferation and differentiation of?

A

uterine epithelial cells

57
Q

what does progesterone stimulate proliferation and differentiation of?

A

stomal cells

58
Q

up until which point can progesterone receptor antagonists induce abortion?

A

7 weeks of gestation.

59
Q

when does the placenta take over the progesterone production?

A

approx 12 weeks.

MSc - embryo exam (13 decks)

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