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RDA > Lecture 11 + 12 - 2018/2017 > Flashcards

Lecture 11 + 12 - 2018/2017 Flashcards

1
Q

How important is the placenta?

A

It’s very important, as it is a person’s first ever organ. In utero a baby eats via the placenta (nourished by maternal blood), and how well the placenta works determines a persons entire life (physiology).

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2
Q

How many women die per year caused by a pregnancy related condition?

A

10 women per 100,000.

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3
Q

How is cardiovascular mortality related to the placenta?

A

Women who develop pre-eclampsia are more likely to develop CVD. If you develop pre-eclampsia by 34 weeks of gestation your risk of dying from CVD has increased - even shortly after pregnancy.

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4
Q

What is the function of the placenta?

A
  1. Self-maintenance/renewal - the placenta needs to grow.
  2. Exchange/transport/transfer - maternal blood nourishes the fetus via the placenta.
  3. Separation - separates mum from babe (separate organisms).
  4. Protection from maternal infections.
  5. Protection from the maternal immune system.
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5
Q

Do maternal blood and fetal blood mix?

A

NO - maternal blood and fetal blood circulations are completely separate - they do not mix. However, the placenta does bring them into close apposition.

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6
Q

What is the placenta?

A

Fetal organ.

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7
Q

What happens around day 7 post fertilisation (day 21 of menstrual cycle) if fertilisation occurs?

A

The blastocyst floats around (free roaming) in the uterine cavity and on day 21 the polar trophectoderm comes into contact with the epithelial cells of the uterus and the polar trophectoderm undergoes differentiation.

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8
Q

What happens in differentiation when the zygote comes into contact with the uterus?

A

All the cells fuse and there is loss of inter-cellular boundaries - they form a cell called the primitive syncytium.

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9
Q

What does the primitive syncytium do in the lacunar stage (day 8-12 post fertilisation)?

A

It invades into the decidua and secretes enzymes which digest it. These enzymes create fluid filled gaps called lacunae.

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10
Q

What happens after lucanae have been formed in the decidua?

A

The trophectoderm is now called trophoblast protrusions - these extend into the lucane to make trabeculae.

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11
Q

What happens after trabeculae are formed?

A

The embryo sinks entirely into one wall of the uterus - the uterus heals around the embryo (embryo is completely covered).

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12
Q

What is the trophectoderm called once the embryo is fully implanted?

A

Trophoblast.

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13
Q

When does the lacunar stage occur?

A

Day 8-12 post fertilisation.

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14
Q

What happens after day 12 post fertilisation?

A

This is when the villous period beings - the primitive syncytium disappears.

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15
Q

What happens in the villous period?

A

The primitive syncytium disappears and cytotrophoblasts proliferate (push from back of embryo underneath syncytium) and become primary villi .

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16
Q

What happens to the lacunar system?

A

It has now become the intervillous space.

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17
Q

What happens at day 14 post fertilisation?

A

Cells of the extra-embryonic mesenchyme invade the primary villi to become secondary villi.

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18
Q

What happens at day 18-20 poster fertilisation?

A

Capillaries form in the secondary villi to become tertiary villi.

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19
Q

Where do vessels in the villi connect to?

A

Umbilical vessels carrying blood to and from the fetus.

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20
Q

What are floating villi?

A

These are villi that do not have contact with the maternal tissues but are suspended in the intervilllous space.

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21
Q

What do floating villi do?

A

They are responsible for the exchange and barrier functions of the placenta.

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22
Q

What are the chorion leave (smooth chorion) made from?

A

The villi that surround the side of the embryo and those that face towards the uterine lumen - they regress to form the smooth chorion.

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23
Q

What the chorion frondosum (definitive placenta) made from?

A

The viili at the base of the implantation site - they form the definitive placenta.

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24
Q

What are anchoring villi?

A

In a few villi some cytotrophoblasts break through the syncytiotrophoblast (outer layer) and spread laterally around the implantation site forming a cytotrophoblast shell.

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25
Q

What is the purpose of the cytotrophoblast shell?

A

The shell remains in contact with the maternal tissue throughout gestation.

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26
Q

What else do the anchoring villi do?

A

Columns of cyotrophoblast continue to stream out of the anchoring villi to invade the decidua (maternal endometrium) and spiral arteries - this occurs during the 1st and 2nd trimester.

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27
Q

What happens to the spiral arteries as the anchoring villi invade them?

A

The extra villous trophoblast have removed the endothelial cells and the smooth muscle cells (which make up the wall of the artery). The spiral arteries are no longer tonically active.

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28
Q

What happens when the spiral arteries are no longer tonically active?

A

This means that the spiral arteries remain open wide (don’t contract) if the mother’s SNS is activated. Normally if spiral arteries were activated by the SNS they would contract and they would keep blood from perfusing the fetus.

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29
Q

What happens if there is inadequate depth of trophoblast invasion in the spiral arteries?

A

There is still tonic control over the arteries. Therefore if the mother’s SNS is activated the spiral arteries will contract and there is a decrease in blood flow to the fetus and the placenta is malperfused. This can result in IUGR/SGA.

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30
Q

What happens if there is reduced number of vessels transformed?

A

There is far less perfusion which can result in a growth restricted baby.

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31
Q

What are the consequences of SGA/IUGR babies?

A

They are more likely to be born prematurely and or be born stillborn.

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32
Q

What happens to the spiral arteries at 10 weeks?

A

They start to plug - the arteries are plugged by endovascular trophoblasts.

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33
Q

What is the purpose of plugging spiral arteries?

A

The plug prevents the passage of maternal red blood cells to the placenta.

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34
Q

What is glandular milk?

A

It is milk which supplies nutrients to the fetus. The uterine gland empties this milk into the inter-villous space. Glandular milk is used for the first 10 weeks instead of blood from the mother.

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35
Q

What is premature blood flow?

A

This is where maternal blood flow is distributed centrally across the placenta pre -mid-gestation, whereas normal maternal blood flow is observed at the peripheries of the placenta.

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36
Q

What can premature blood flow cause?

A
  1. Miscarriage.

2. Miss miscarriage - signs of an impending miscarriage.

37
Q

Define villous?

A

Branch of the placenta.

38
Q

Define villous cytotrophoblast?

A

Trophoblast porgenitor cell type that is found mainly in the first trimester, it underlies the syncytiotrophoblast.

39
Q

Define Syncytiotrophoblast?

A

This is the surface layer of the placenta that is formed by fusion of the VCTB. STB does not replicate but is replaced by fusion of the additional villous cytotrophoblast (VCTB).

40
Q

Define exravillous cytotrophoblast?

A

These are differentiated cells that have migrated out of the villous placenta towards the maternal tissues.

41
Q

What structural changes occur during early pregnancy?

A

Stroma (loose mesenchymal core) of the villi become more cellular and vascularised.

42
Q

What structural changes happen during the second trimester?

A

Villous cytotrophoblast (single layer) starts to thin down.

43
Q

What structural changes happen during the third trimester?

A

Villous cytotrophoblast is sparse.

44
Q

What other structural changes occur during the pregnancy?

A
  1. Branching of the villi increase.

2. Size of the placenta increases.

45
Q

What happens in the decidual reaction?

A
  1. Stromal cells (fibroblasts) of the decidua swell up and store glycogen.
  2. Upon implantation in the decidua (functional layer) this reaction is enhanced.
46
Q

What is the purpose of storing glycogen in the stromal cells of the decidua?

A

It is an energy source for the implanting embryo.

47
Q

What is the decidua basalis?

A

The decidua that underlies the implantation site. It sits directly in front of the placental disc.

48
Q

Where does transformation of the spiral arteries occur?

A

Decidua basalis.

49
Q

What is the decidua capsularis?

A

The decidua that overlies the implantation site. Sits between the uterine lumen and the placenta.

50
Q

What is the decidua peritalis?

A

The decidua around the remainder of the uterus.

51
Q

What happens to the decidua as gestation progresses along?

A

The amniotic cavity enlarges and eventually obliterates the uterine cavity. The decidua capsularis then fuses with the decidua peritalis.

52
Q

What is the amnion placental membrane?

A

Avascular membrane that covers the cord and placenta.

53
Q

What is the chorion placental membrane?

A

Vascular membrane that contains fetal vessels.

54
Q

Is the decidua a fetal membrane?

A

No it is not. It is derived from the decidua capsularis and peritalis.

55
Q

Where does the umbilical cord come from?

A

The yolk sac and the allantois (outgrowth of primitive fetal gut).

56
Q

Where are the vessels of the umbilical cord derived from?

A

Allantois.

57
Q

What vessels are in the umbilical cord?

A

2 arteries and 1 vein (umbilical vein carries oxygenated blood).

58
Q

What lines the umbilical cord?

A

Whartons Jelly.

59
Q

What is Whartons jelly?

A

Networkd of myofibroblasts (contractile) with spaces of mucopolysaccharides.

60
Q

Why is whartons jelly important?

A

It keeps the umbilical cord turgid (the mucopolysaccharides do this). It prevents the cord from collapsing and stops the baby from pulling the cord tight.

61
Q

What is a false knots in the umbilical cord?

A

these are varicosities in the vessel (vessel is ballooned out - no significance).

62
Q

What are true knots in the umbilical cord?

A

These are knots that can pull the cord and occlude the artery and vein, hence decreasing the blood flow to the fetus.

63
Q

What happens when the mucopolysaccharides get dehydrated?

A

Whartons Jelly won’t work and it can allow the cord to tighten and for true knots to form.

64
Q

How does the placenta increase transport? (placental adaptations)

A
  1. Villous structure is tortous with a large surface.
  2. Syncytiotrophoblast has a microvillous structure - this increases the area for transfer.
  3. In the third trimester most villi are small tertiary villi.
  4. In the third trimester the fetal capillaries are closely apposed to the syncytiotrophoblast.
65
Q

What is the difference between fetal blood and maternal blood?

A

Fetal blood is greater adapted for oxygen exchange - it has greater affinity for oxygen due to Hbf (fetal at 80% will adult at 50%). Essentially fetal blood has more haemoglobin and can carry more oxygen than maternal (adult blood).

66
Q

Describe the bohr effect in terms of the fetus?

A

As maternal blood picks up fetal metabolites, there is a decrease in PH, this decreases the affinity for oxygen and an increase in dissociation of oxygen occurs on the mothers side. Double bohr effect occurs on the fetal side - fetus sucks oxygen off mother.

67
Q

Describe the haldane effect?

A

The capacity of haemoglobin to bind to carbon dioxide is related to the amount of bound oxygen. If oxygen is lost from maternal blood the capacity for carbon dioxide increases. Double haldane effect occurs on the fetal side - mother sucks carbon dioxide off fetus.

68
Q

What are the functions of amniotic fluid?

A
  1. Buoyant medium that allows the fetus to float around and to allow for symmetrical growth.
  2. Cushions the fetus/embryo.
  3. Prevents adhesions of the fetus with the membranes.
  4. Allows the fetus to move - muscle development.
  5. Development of the GI/resp tracts - allows the baby to practice swallowing and breathing movements which are crucial post birth.
69
Q

What are the amniotic fluid origins?

A
  1. Initially it is ultra filtrate from the maternal plasma.
  2. Fetal contribution starts to become the dominant contribution.
  3. By 20+ weeks it’s mainly fetal urine and also from the surface of placenta and cord.
70
Q

What happens to amniotic fluid volume as gestation occurs?

A 
10 weeks = 30mls.
20 weeks = 250mls.
35 weeks = 1000mls.
Term = 800mls.
Post-term = 500-600mls.
71
Q

What is the human fetal urine output per day?

A

500-1200mls per day.

72
Q

What is the pathway for amniotic fluid?

A
  1. Fluid leaves the amniotic cavity mainly by fetal swallowing (500-1000ml a day).
  2. Fluid can move across the fetal skin (prior to keratinisation at 24 weeks).
  3. Fluid can move across the fetal membranes into:
    i) maternal circulation (minor).
    ii) fetal vessels of placenta and umbilical cord (major).
73
Q

What is polyhydraminos?

A

Excess amniotic fluid. It is possibly due to loss of swallowing, and is found in many cases of gestational diabetes.

74
Q

What is oligohydraminos?

A

Lack of amniotic fluid. It is potentially due to fetal kidney problems.

75
Q

How can we use amniotic fluid for diagnostic purposes?

A
  1. Amniocentesis - put a needle into the amniotic fluid at 14-16 weeks gestation.
  2. Chorionic Villous Sampling (CVS) - can sample it via transvercially or transabdominally via ultrasound guidance. This is done at around 8-10 weeks.
76
Q

What problems can occur with diagnostic testing via amniocentesis OR CVS?

A

Miscarriage can occur. Amniocentesis has low loss rates, whereas CVS can have rates up to 5%.

77
Q

How else can you find out about genetic information about the baby?

A

Finding syncytial nuclear aggreates (these bud off the placenta and are found in maternal blood). This is a non-invasive test.

78
Q

What infections do the placenta protect the baby from?

A
  1. Hep B - however the baby can pick it up during parturition.
  2. Rabies.
  3. Measles.
  4. Malaria - however it can cause clogging of the placenta.
79
Q

What infections do the placenta not protect the baby from?

A
  1. HIV.
  2. CMV.
  3. Small pox and other related viruses.
  4. Rubella.
  5. Toxoplasmosis - get this from cats and raw meat.
80
Q

When does the critical organogenesis period occur?

A

20-70 days after the first day of the LMP.

81
Q

What is important about this period in regards to drug taking?

A

Drugs transferred during this period may cause serious damage e.g. thalidomide. Half the time mothers do not know they are pregnant so they take drugs during this critical period.

82
Q

What drugs are dangerous during the critical organogenesis period?

A
  1. Thalidomide - can cause limb reduction defects.
  2. Diethylstilbestrol (DES) - can cause cancer (clear cell adenocarcinoma) in the vagina or cervix of adults after in utero exposure. Basically babies who were exposed to it in utero can get cancer when older.
83
Q

What is betamethasone?

A

Glucocorticoid (steroid) that is given to mum who is going into pre-term labour. It reduces the incidence of respiratory distress syndrome.

84
Q

How can ethanol affect the baby?

A

Ethanol can cross the placenta and can cause fetal alcohol syndrome or stillbirth.

85
Q

How can recreational drugs affect the baby?

A

They may cause intrauterine growth restrictions and developmental delay.

86
Q

How can paracetamol and aspirin affect the baby?

A

It can not. It is a safe drug for the mother to take.

87
Q

How can heparin affect the baby?

A

It can not. It is a safe drug for the mother to take.

88
Q

How can warfarin affect the baby?

A

It crosses the placenta and can cause fetal malformations.

RDA (19 decks)

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