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BRS Y2 > Pregnancy, Parturition and Foetal Development > Flashcards

Pregnancy, Parturition and Foetal Development Flashcards

1
Q

What type of nutrition is used during early embryo development

A

Histotrophic, this is nutrition originating from the degradation of local endometrial tissue

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2
Q

When does the switch to heamotrophic nutrition in the fetus occour?

A

At the start of the second trimester

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3
Q

How is haemotrophic nutrition used?

A

Through a haemochorial-type placenta where maternal blood directly contacts the fetal membranes

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4
Q

What is the amnion derived from?

A

The epiblast

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5
Q

What does the amnion form?

A

The amniotic cavity and then becomes part of the amniotic sac

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6
Q

What does the connecting stalk link?

A

It links the developing embryo unit to the chorion

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7
Q

What are trophoblastic lacunae?

A

large spaces filled with maternal blood formed by the breakdown of maternal capillaries and unterine glands

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8
Q

What do the trophoblastic lacunae become?

A

Intervillous spaces aka maternal blood spaces

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9
Q

What is the chorion?

A

The second fetal membrane

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10
Q

What are the names of the inner and outer fetal membranes?

A 
Inner= amnion
Outer= chorion
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11
Q

When does the amnion begin to secrete amniotic fluid?

A

Week 5

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12
Q

What does the chorion originate from?

A

From yolk sac derivative and the trophoblast

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13
Q

What is the blood supply to the chorion like?

A

Highly vascularised

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14
Q

What does the chorion give rise to?

A

The chorionic villi

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15
Q

What is the allantois?

A

An outgrowth of the yolk sac, it grows along the connecting stalk from the embryo to the chorion

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16
Q

What does the allantois become and how?

A

It becomes coated with mesoderm and vascularises to become the umbilical chord

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17
Q

What does the umbilical chord arise from?

A

The allantois

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18
Q

What are the 2 layers of the amniotic sac?

A

The amnion and the chorion

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19
Q

How does the chorion give rise to chorionic villi?

A

The cytotrophoblast forms finger like projections through the syncitiotrophoblast layer into the maternal endometrium

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20
Q

What is the role of the chorionic villi?

A

They provide extra surface area for exchange of gases and nutrients

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21
Q

What are the 3 phases of chorionic villi development?

A

Primary: outgrowth of the cytotrophoblast and branching of these extensions
Secondary: growth of the fetal mesoderm into the primary villi
Tertiary: growth of the umbilical artery and umbilical vein into the villus mesoderm, providing vasculature.

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22
Q

Describe the villus microstructure

A

There is a convoluted knot of vessels and vessel and dilation to slow blood flow and allow efficient exchange , then the whole structure is coated in trophoblast

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23
Q

Describe the maternal blood supply to the endometrium

A

Uterine arteries branch into arcuate arteries, these branch into radial arteries, these branch into basal arteries, these form spiral arteries

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24
Q

What happens to the maternal blood supply to the endometrium if implantation doesn’t occur?

A

The spiral arteries regress and the endometrium is lost

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25
Q

What arteries provide blood supply to the endometrium?

A

Spiral arteries

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26
Q

What is the name of the process by which blood supply to the maternal endometrium is established?

A

Conversion

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27
Q

Describe the process of conversion (in establishing blood supply to the endometrium)

A

Turns the spiral artery into a low pressure, high capacity conduit for maternal blood flow

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28
Q

By what process is oxygen exchanged across the placenta?

A

Via diffusional gradient (maternal oxygen tension is high and fetal is low)

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29
Q

By what process is glucose exchanged across the placenta?

A

Facilitated diffusion by transporters on maternal side and fetal trophoblast cells

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30
Q

By what process is water exchanged across the placenta?

A

Mainly diffusion but also some local hydrostatic gradient

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31
Q

By what process are electrolytes exchanged across the placenta?

A

Diffusion and active co-transport

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32
Q

By what process is calcium exchanged across the placenta?

A

Actively transported against a concentration gradient by magnesium ATPase calcium pump

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33
Q

By what process are amino acids exchanged across the placenta?

A

Active transport

34
Q

How does maternal cardiac output change in pregnancy?

A

Increases 30% in the fist trimester

35
Q

How does maternal PVD change in pregnancy?

A

Decreases up to 30%

36
Q

How does maternal blood volume change in pregnancy?

A

Increases to 40%

37
Q

How does maternal pulmonary ventilation change in pregnancy?

A

Increases 40%

38
Q

Describe fetal oxygen tension, content and saturation in comparision to maternal blood

A

Oxygen tension is lower

Oxygen content and saturation are similar to maternal blood

39
Q

How much oxygen and glucose that is supplied does the placenta consume?

A

40-60%

40
Q

How does the fetal circulatory system work?

A

Placenta acts as site of gas exchange for fetus
Ventricles act in parallel rather than series
Vascular shunts bypass pulmonary & hepatic circulation but close at birth

41
Q

When do fetal movements begin?

A

Late first trimester

42
Q

When does the fetal endocrine pancreas function and insulin production start?

A

Start of second trimester

43
Q

Define labour

A

The safe expulsion of the fetus at the correct time

44
Q

How many phases of labour are there and what are they called?

A

Phase 1= quiescence (prelude to parturition)
Phase 2= activation (preparation for labour)
Phase 3= stimulation (process of labour)
Phase 4= involution (parturient recovery)

45
Q

What is the difference between the stages and phases of labour?

A

There are 4 phases of labour and then in phase 3 there are 3 stages of labour itself

46
Q

What are the 3 stages of labour?

A

Stage 1= contractions start and cervix dilates
Stage 2= delivery of fetus at full dilation of the cervix with maximal myometrial contractions
Stage 3= delivery of placenta and fetal membranes and post partum replair

47
Q

In stage 1 of labour what are the 2 phases of cervix dilation?

A

Latent phase= slow dilation of the cervix to 2-3cm

Active Phase= rapid dilation of the cervix to 10cm

48
Q

What length is a fully dilated cervix?

A

10 cm

49
Q

What characteristics of a pro inflammatory reaction is seen in labour?

A

Infiltration by immune cells

Inflammatory cytokines and prostaglandin secretion

50
Q

What structure is important in containing the fetus in the uterus?

A

The cervix, it does this by the high connective tissue content

51
Q

When does cervical softening occur?

A

Begins in the first trimester

52
Q

When does cervical ripening occur?

A

Weeks and days before birth

53
Q

What happens in ripening of the cervix?

A

Monocyte infiltration and IL-6 and IL-8 secretion

Hyaluron deposition

54
Q

What are the 4 stages of cervix remodelling in pregnancy?

A

Softening
Ripening
Dilation
Post partum repair

55
Q

What hormone is important in initiating labour?

A

Corticotrophin releasing hormone (CRH)

56
Q

What are the functions of CRH in labour?

A

Promotes fetal ACTH and cortisol release

Stimulates DHEAS production by the fetal adrenal cortex, this is a substrate for estrogen production

57
Q

How does CRH bioavailability increase near labour?

A

Theres a decline in CRH binding protein levels

58
Q

What are progesterone levels during pregnancy and why?

A

High to maintain uterine relaxation

59
Q

What happens to progesterone receptor isoforms near term?

A

Wwitch from PR-A isoforms of progesterone receptor (activating) to PR-B and PR-C (repressive) isoforms expressed in the uterus

60
Q

What happens to estrogen receptor expression near term in pregnancy?

A

There is a rise in estrogen receptor alpha expression

61
Q

What happen to the receptivity of the uterus to estrogen and progesterone near term?

A

Uterus becomes ‘blinded’ to progesterone action and sensitized to estrogen action but levels of both hormones are high

62
Q

Where is oxytocin synthesised?

A

Synthesized mainly in the utero-placental tissues and pituitary

63
Q

When does oxytocin production increase?

A

Increases sharply at the onset of labour

64
Q

What drives a rise in oxytocin levels?

A

Estrogen levels, as they rise more oxytocin receptors are expressed

65
Q

What reflex causes a sharp rise in oxytocin levels?

A

Ferguson reflex

66
Q

Describe the Ferguson reflex

A

As foetus bears down onto the cervix stretch receptors they signal to the hypothalamus
This triggers eventual release of oxytocin from the posterior pituitary into maternal circulation
It acts on the uterus/ myometrium

67
Q

Before labour what inhibits oxytocin receptor expression?

A

Progesterone

68
Q

What are the functions of oxytocin?

A

Increases connectivity of myocytes in myometrium (syncytium)- promotes formation of gap junctions
Destabilises membrane potentials to lower threshold for contraction
Enhances liberation of intracellular Ca2+ ion stores

69
Q

What are the main prostaglandins synthesised in labbour?

A

PGE2
PGF2alpha
PGI2

70
Q

How does estrogen drive prostaglandin levels?

A

Rising estrogen activates phospholipase A2 enzyme, generating more arachidonic acid for PG synthesis
Estrogen stimulation of oxytocin receptor expression promotes PG release

71
Q

What enzyme is involved in prostaglandin synthesis?

A

Phospholipase A2

72
Q

What is the role of PGE2?

A

Cervix re-modelling

It promotes leukocyte infiltration into the cervix, IL-8 release and collagen bundle re-modelling

73
Q

What is the role of PGE2 alpha?

A

Myometrial contractions

Destabilises membrane potentials and promotes connectivity of myocytes (with oxytocin)

74
Q

What is the role of PGI2?

A

Promotes myometrial smooth muscle relaxation and relaxation of lower uterine segment

75
Q

Describe the positive feedback loop involving CRH and cortisol

A

Foetus pituitary produces CRH
CRH acts of foetal adrenal
Foetal adrenal produces cortisol
Cortisol encourages placental production of CRH

76
Q

What is the role of DHEAs produced by the fetus?

A

DHEAS are converted to oestrogen in the placenta
Oestrogen acts on myometrium promoting expression of oxytocin receptor so uterus becomes sensitive to oxytocin
Oxytocin triggers contractions

77
Q

What pattern do myometrial contractions follow?

A

Contractions start from the fundus and spread downwards

This causes lower segment and cervix to be pulled up forming birth canal

78
Q

What are the type of muscle contractions in labour?

A

Brachystatic, fibres do not return to full length on relaxation

79
Q

How does the position of the fetus in the womb change before and during delivery?

A

There is pressure on the fetus’ chin so it presses against the chest (flexion)
The fetus then rotates (belly to mother’s spine) so the head is expelled first when the cervix dilates

80
Q

What helps expel the placenta and fetal membranes after the fetus is deilvered?

A

There is rapid shrinkage of the uterus causing the area of contact with the placenta with the endometrium to shrink and causing the fetal membranes to shrink

81
Q

What state does the uterus stay in after delivery and why?

A

It remains contracted to facilitate uterine vessel thrombosis

BRS Y2 (85 decks)

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