Repro Session 8 Flashcards Preview

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Flashcards in Repro Session 8 Deck (142):
1

What does the yolk sac become after the primitive gut tube has formed?

Proximal umbilical cord

2

What causes the amniotic sac to increase in size?

Foetus and fluid

3

What is the chorionic sac occupied by?

Expanding amniotic sac

4

What obliterates the chorionic cavity?

Amniochorion formation

5

What are the aims of implantation?

Establish basic unit of exchange, anchor placenta and to establish maternal bloodflow

6

How is the basic unit of exchange established in implantation?

Villi development

7

Describe the different stages of villi in their development.

Primary: early finger-like projections of trophoblast
Secondary: invasion of mesenchyme into core
Tertiary: invasion by foetal BV

8

Why is implantation said to be interstitial?

Uterine epithelium is breached and the conceptus implants in the stroma

9

Why is the placental membrane said to be haemomonochorial during implantation?

1 layer of trophoblast between maternal blood and foetal capillaries

10

Is there usually mixing of maternal and foetal blood?

No due to haemomonochorial placental layer

11

How is the placenta anchored in implantation?

Establishment of outermost cytotrophoblast shell

12

What has happened in embryonic development by the end of the 2nd week?

Conceptus has implanted; embryo, amniotic cavity and yolk sac are suspended by the connecting stalk in the chorionic cavity

13

What are the alternative names of the smooth and villous chorion?

Smooth = chorionic sac. Villous = placenta

14

What can uncontrolled invasion by the blastocyst at an inappropriate site of implantation lead to?

Haemoperitoneum

15

What is placenta praevia?

Implantation in lower 1/3 of uterine segment

16

When is C-section necessary in placenta praevia?

If internal os is occluded

17

What is there a risk of in placenta praevia?

Haemorrhage

18

What is placenta accreta?

Excessive invasion of chorionic villi

19

How do placenta accreta, increta and percreta differ?

Accreta = invasion of myometrium
Increta = into myometrium
Percreta = through myometrium

20

What is the pathogenesis of pre-eclampsia?

Failure of epithelial to endothelial transformation at 20+ wks results in unknown circulating factor causing maternal hypertension and proteinuria

21

What is the cycle of events in placental insufficiency?

Failure of maternal artery remodelling to low resistance; increased vascular resistance in fetoplacental vascular bed; deceased metabolically active placenta

22

What are prepared in each uterine cycle in anticipation of implantation?

Pre-decidual cells

23

Why can pre-decidual cells be considered "check point" cells?

Decidual reaction provides balancing force for invasive trophoblast

24

How far does the trophoblast invade into the endometrium normally?

To spiral arterioles but no further

25

What happens when the cytotrophoblast from ends of anchoring villi attach to terminal ends of spiral arteries?

Undergo epithelial to endothelial transformation

26

How are the BV of the endometrium altered upon implantation?

From small diameter with high resistance to large diameter, low resistance vessels

27

How do the villi on the surface of the chorion develop?

Those on chorionic pole grow to form chorion frondosum. On aembryonic pole they degenerate to form chorion laeve

28

What decidua layer covers the chorion frondosum?

Basalis

29

What is the decidua basalis?

Decidual plate with glycogen that will form placenta

30

What happens to the decidua capsularis membrane over the chorion laeve?

Stretches and degenerates

31

What does the chorion laeve fuse with?

Uterine wall

32

How can foetal membranes be shared by monozygotic twins?

One zygote with separate implantation sites--> 2 amnions and chorions. One morula with 2 intracellular masses and bilaminar discs forms 2 amnions and 1 chorion. One blastocyst and bilaminar disc with 2 primitive streaks forms shared amnion and chorion

33

What is there a risk of in a shared amnion and chorion between monozygotic twins?

Twin-to-twin transfusion

34

What layers are present in the first trimester placenta?

Complete syncytiotrophoblast and cytotrophoblast layer

35

What forms the foetal component of the first trimester placenta?

Trophoblast with secondary and tertiary villi and extramebryonic mesoderm (chorionic plate)

36

What forms the maternal component of the first trimester placenta?

Uterine endometrium

37

What are stem villi?

Extensions of mesoderm from chorionic plate to cytotrophoblast shell to give extraembryonic vasculature

38

What happens in endovascular invasion of the first trimester placenta?

Maternal vessels are eroded so that blood flows into intevillous spaces

39

How do the stem villi in the first trimester placenta?

Free villi extend from them

40

What happens to the syncytium in the first trimester placenta?

Becomes thin and breaks off as syncytial knots in maternal circulation

41

How does the foetal aspect of the placenta appear?

Umbilical vessels radiate to chorionic vessels under transparent amnion

42

How does the maternal aspect of the placenta appear?

Surrounding amniochorion ruptured, cotyledons separated by decidual septa and covered by thin layer of decidua basalis

43

What changes have occurred from the first trimester to term placenta?

SA for exchange dramatically increased, placental barrier thin, cytotrophoblast layer lost, discoid with 15-25 cm diameter

44

Why is a small population of cytotrophoblast cells retained in the term placenta?

For repair

45

What blood vessels are present in the umbilical cord?

2 umbilical arteries carrying deoxygenated blood from foetus to mother and 1 umbilical vein carrying oxygenated blood from placenta to foetus

46

Which blood vessels in the umbilical cord are oxygen rich and poor?

Umbilical arteries are oxygen poor, veins oxygen rich

47

What are the metabolic functions of the placenta?

Synthesis of glycogen, cholesterol and fatty acids

48

Why does the latent a synthesis cholesterol?

For steroid hormone synthesis

49

What are the endocrine functions of the placenta?

Produce protein and steroid hormones

50

What protein hormones does the placenta produce?

hCG, hCsommatomammotrophin (placental lactogen), hCthyrotrophin, hCcorticotrophin

51

What is hCG and analogue of?

LH

52

What is the function of placental lactogen?

Diabetogenic mother and breast development

53

What steroid hormones does the placenta synthesise?

Progesterone and oestrogen

54

What effect does progesterone have on appetite in the pregnant female?

Increases

55

Why do trophoblast disease and choriocarcinoma cause very raised hCG?

Endocrine function of placenta is in syncytiotrophoblast

56

What does the placenta take over steroid hormone production from in the 11th week?

Corpus luteum

57

What happens to hCG levels when the placenta takes over steroid hormone production?

Decrease

58

What is a molar pregnancy?

When the outer cell mass only develops

59

What is choriocarcinoma?

Malignant trophoblast if cancer

60

How is exchange of water, electrolytes, urea and uric acid achieved by the placenta?

Simple diffusion

61

How is AT of a.a. And iron achieved by the placenta?

Specific transporters in syncytiotrophoblast

62

How is glucose transported across the placenta?

Facilitated diffusion

63

Describe gas exchange across the placenta.

O2, CO2 and CO via simple diffusion limited by flow

64

Why does gas exchange across the placenta need careful monitoring, especially in childbirth?

Cord compression can be rapidly fatal as foetal oxygen stores are small

65

What makes complement components in the first trimester?

Foetus

66

What happens at 14wks that causes development of passive immunity for the foetus?

Maternal IgG transported via receptor-mediated process so foetal [IgG] exceeds those in maternal circulation

67

What does development of passive immunity depend on?

Mother's exposure to pathogens

68

Is the placenta a protective or true barrier and why?

Protective because some substances readily access foetus via placenta

69

Give some examples of known teratogens.

Thalidomide, alcohol, therapeutic drugs, drugs of abuse

70

What effect does maternal smoking have on pregnancy via an unknown mechanism?

Causes embryon and placental disruption

71

How do infectious agents lead to birth defects?

Cross placenta to cause foetal infection and subsequent cell death

72

Give some examples of infectious agents that can lead to birth defects.

Varicella zoster, CMV, treponema pallidum, toxoplasma gondii, rubella

73

What is rubella syndrome?

Microcephaly, PDA and cataracts

74

What is the affect of alcohol crossing the placental barrier?

Inhibits bronchial apparatus and CNS development

75

How does haemolytic disease of the newborn arise?

Exposure of maternal blood to foetal circulation mounts maternal antibodies against foetal rhesus group which in a following pregnancy cross placenta and ellicit haemolysis

76

Why is haemolytic disease of the newborn now uncommon?

Mother and father rhesus groups are tested and prophylaxis offered if necessary

77

How is routine antenatal screening conducted?

History and examination for risk factors and FHx, blood tests and urinalysis

78

What is assessed in antenatal blood tests?

Blood group for comparison with father's, Hb levels for anaemia and any infection

79

Why is UTI a potential problem pregnancy?

Can lead to pre-term labour

80

What change is seen in cardiac output during pregnancy?

Increase of 40% from T1

81

What change is seen in stroke volume during pregnancy?

Increase of 35% from T1

82

Why does cardiac output increase in pregnancy?

To account for potential significant haemorrhage at birth

83

Why does stroke volume increase in pregnancy?

Blood volume has significantly increased

84

What changes are seen in TPR during pregnancy?

Decreases 25-30% from T1

85

Why does TPR change during pregnancy?

Foetal gas exchange depends on flow

86

How does blood pressure change during pregnancy?

Decreases during T1 and T2 but returns to normal in T3

87

What causes blood pressure changes during pregnancy?

Decreased vascular resistance due to progesterone

88

Why should women in T3 not lie on their back?

Causes aortocaval compression by gravid uterus leading to hypotension

89

What is the treatment for pre-eclampsia?

Deliver baby

90

How is pre-eclampsia identified?

Maternal hypertension and proteinuria

91

What changes in renal perfusion are seen during pregnancy?

Increases by 60-80%

92

Why does RPF change in pregnancy?

Cardiac output increases

93

What change is seen in GFR during pregnancy?

Increases of 55%

94

Why does GFR change in pregnancy?

Progesterone causing afferent and efferent dilation

95

What complications can progesterone action on GFR cause?

Hydroureter and urinary stasis

96

What change is seen in creatinine clearance in pregnancy?

Increases by 40-50%

97

What happens in protein excretion during pregnancy?

Increases

98

What happens to urea levels during pregnancy?

Decreases by 50%

99

What accounts for the changes in creatinine clearance, protein excretion and urea levels in pregnancy?

Filtration capacity of kidneys

100

What change is seen in bicarbonate levels during pregnancy?

Decreased

101

What change is seen in creatinine levels during pregnancy?

Decreases

102

Why does the bicarbonate level change during pregnancy?

Functional renal reserve decreases as GFR increases

103

What do normal non-pregnant ranges of urea, bicarbonate and creatinine indicate in pregnancy?

Renal dysfunction

104

What respiratory changes are seen during pregnancy?

Oxygen consumption increases, resting minute ventilation increases, tidal volume increases, RR VC and FEV1 remain constant

105

What causes physiological dyspnoea during pregnancy?

Increased respiratory drive due to progesterone

106

Why does tidal volume increase during pregnancy?

AP and transverse diameters of thorax increase

107

Why does FRC decrease in T3?

Diaphragm is displaced by gravid uterus

108

Why are vital capacity and FEV1 constant in pregnancy?

Diaphragm and changes in thorax diameters balance each other out

109

Why is PaCO2 reduced in pregnancy?

Increased metabolic CO2 is blown off by physiological hyperventilation

110

Why does physiological hyperventilation not lead to respiratory alkalosis?

Renal bicarbonate excretion increases

111

Why are pregnant women predisposed to metabolic acidosis?

Renal bicarbonate excretion is increased

112

What changes to carbohydrate metabolism are seen on pregnancy?

Increased maternal peripheral insulin resistance, switch to gluconeogenesis

113

What stimulates changes to carbohydrate metabolism in pregnancy?

Human placental lactogen mainly but prolactin, oestrogen, progesterone and cortisol also contribute

114

What happens to fasting blood glucose pregnancy?

Decreases

115

What happens to post-prandial blood glucose in pregnancy?

Increases

116

What is gestational diabetes?

Carbohydrate intolerance first recognised in pregnancy that does not persist after delivery

117

What are risk factors for developing gestational diabetes?

PCOS, FHx, high maternal age, T2DM, ethnicity, obesity

118

What are the possible consequences of gestational diabetes?

Macrosomic foetus, stillbirth, congenital defects

119

What builds fat stores in early pregnancy for lipolysis in T2?

Progesterone

120

What is the benefit of lipolysis in T2?

Increases plasma free FA that cannot cross placenta therefore increasing glucose available for foetal metabolism

121

Which fatty acids are able to cross the placenta?

Essential

122

Why are pregnant women at a higher risk of ketoacidosis?

Increased FA synthesis combined with physiological increase in renal bicarbonate excretion

123

Why might TSH be low in normal pregnancies?

hCG minimises its function

124

Why does hCG and TSH not lead to high free T4?

Very active liver produces thyroid binding globulins

125

What happens to the appendix during pregnancy?

Moved to RUQ

126

What are the effects of progesterone on the smooth muscle of the GI tract?

Delayed emptying and stasis in biliary tract

127

Why are pregnancy women at an increased risk of pancreatitis?

Progesterone on smooth muscle of biliary racy causes stasis and stone formation

128

Why is pregnancy a pro-thrombotic state?

Need for fibrin deposition at the implantation site and risk of haemorrhage at birth

129

What are the effects of progesterone on the blood during pregnancy?

Increased fibrinogen and clotting factors, decreased fibrinolysis, stasis and venodilation

130

Why can thromboembolic disease in pregnancy not be treated with warfarin?

It is a teratogen

131

How does a physiological aneamia arise during pregnancy?

Due to dilution as red cell mass increases but does not match the plasma volume increase

132

When does iron and folate deficiency anaemia arise in pregnancy?

If increased demands during pregnancy are not met

133

What are the complications of sickle cell disease in pregnant homozygotes?

More frequent crises, pre-eclampsia, thrombosis and infections

134

What are the consequences of sickle cell disease in pregnancy heterozygotes?

May develop crises

135

What are the implications for pregnancy for homozygous beta-thalassaemia pts?

Anaemia in pregnancy is unusual due to iron overload

136

What is the treatment for pregnant homozygous beta-thalassaemia pts with anaemia?

Folic acid without iron

137

What are the consequences for heterozygous beta-thalassameia pts during pregnancy?

Worsening of chronic anaemia

138

Why is non-specific local immune system suppression needed at the materno-foetal interface?

Foetus is an allograft

139

How is the immune system suppression at the materno-foetal interface identified histologically?

Different lymphocytes are found at the trophoblast-endometrial boundary

140

How can a foetus develop an abnormal thyroid state?

Exchange of maternal autoantibodies e.g. In Graves or Hashimoto's disease

141

What is the treatment for haemolytic disease of the newborn?

IM anti-RH antibodies

142

How does the treatment for haemolytic disease of the newborn act?

Foetal rhesus D+ve destroyed before mother mounts response