Endocrinology: Placental structure and function Flashcards

1
Q

What are the 3 stages of implantation

A

Appoisition: Contact of polar trophoblast and endometrium Endometrium develops pinopodes.
Adhesion: Destructions of the zona pellucida
Penetration: Trophoblast invasion, active transport of metabolic substrates.

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2
Q

Explain the anatomy of the developing placenta.

A

2 layers: inner cytotrophoblast (cell walls) syncytiotrophblast (no cell wall)

At 9 days: 2 layers, within synscytiotrophoblast lacunae form → later form intervillous space

Day 17: Primary stem villous form - outgrowth of cytotrophoblast, inner core of extraembryonic mesoderm

Day 22: Form primary villi

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3
Q

until how many weeks does the placenta weigh more than the foetus

A

17weeks

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4
Q

How is blood flow to the placenta increased in pregnancy?

A

Trophoblast invasion of the spiral arteries of the decidua & outer myometrium,

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5
Q

Name 2 observations seen between placental architecture between healthy placenta and PET placenta

A
  • Placental Villi are less developed, fewer branches and less complex vascular loops
  • Change in spiral artery architecture
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6
Q

What feature makes the trophoblast open to potential allogenic immune response by the mother?

A

No epithelial barrier

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7
Q

Are uterine NK cells the same as plasma NK cells.

A

No
Reduced cytotoxicity
Diagnostic test of NK cells in peripheral blood give no information about uterine cell function

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8
Q

When does uncontrolled trophoblast invasion occur?

A

Lack of decidual response → e.g. tubal ectopic or scar tissue within the uterus

Haemorrhage without intervention

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9
Q

What is inadequate invasion of decidua and spinal arteries associated with?

A

Reduced blood supply to the placental bed & growth restriction, hypoxic fetus

  • PET
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10
Q

if fetal cells become in contact with maternal circulation why is there not T- or B- immune response?

A

Syncytiotrophoblast expresses no MHC antigens

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11
Q

What are the 2 points of contact between the placental trophoblast and maternal immune system

A

1) Villous syncytiotrophoblast is bathed in maternal blood

2) Extravillous cytotrophoblast interacts with uterine tissue.

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12
Q

Does the Extravillous cytotrophoblast produce MHC

A

Yes - HLA C,G,E not clear why doesn’t cause immune response

→ Uterine NK cells react but seem to enhance blood supply

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13
Q

What substances can cross the placental barrier?

A

Low molecule weight molecules: gases, Na, urea and H20

Non polar molecules: unconjugated steroids, fatty acids

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14
Q

What is the double Bohr effect & why is it important in O2 exchange

A
  1. Fetal Hb had greater affinity for O2 that maternal Hb
  2. Placenta has high pH (great affinity for O2) whilst maternal blood becomes more acidic due to CO2 - maternal Hb more likely to release O2
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15
Q

How does maternal relative insulin sensitivety help the developing fetes.

A

High blood glucose and less taken up by maternal tissue

Placental converts 1/3 to lactate

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16
Q

Explained the change of amino acid materialism in pregnancy

A

Reduced deamination of amino acids in maternal liver, reduced excretion of urea. More amino acids available for fetes. Contraction of amino acids 5 x higher in trophoblast than maternal blood. Urea generated crosses back into maternal blood

17
Q

What is the volume of amniotic fluid at
8 weeks
20 weeks
34 weeks

A

15ml
450ml
750ml

18
Q

What are the 2 layers of placental membranes?

A

Chorion (cuboidal epithelium)

Amnion

19
Q

What is the role of bHCG in early pregnancy.

A

produced by the syncytiotrophoblast from 6-7 days post fertilisation - bind to corpus lute to stop it breaking down → continue to produce progesterone

20
Q

What other hormones if bHCG structurally similar too>

A

LH

a group → FSH, TSH

21
Q

What time is the peak of bHCG

A

12 weeks

22
Q

Although the corpus luteum is present throughout pregnancy, when is it progesterone no longer essential

A

6 weeks

23
Q

Where is progesterone produced during pregnancy

A

Trophoblast

24
Q

What is the main oestrogen of pregnancy?

A

Estriol (not 17-estradiol in the ovarian cycle)

25
Q

Does the production or estriol depend on the presence of a fetus? WHY?

A

Yes - unlike progesterone

Estriol is produced in the placenta but uses DHEA which is produced in the fetal adrenal glands and then hydroxylated in the fetal liver.

26
Q

How much does the maternal estriol concentration increase?

A

100x

27
Q

When is human placental lactose produced and what is it similar too

A

End of 1st trimester when bHCG production stops

Similar to prolactin and pituitary growth hormone

28
Q

If cleavage of the blastomere occurs at day 4-8 what type of twins
What are these twins at risk of

A

Monochorionic Diamniotic

Twin to twin tranfusion

29
Q

If the cleavage occurs after day 8 what types of twins

A

Monochorionic Monoamnitoic

30
Q

What is the pathophysiology of a complete molar pregnancy?

A

Maternal chromosome are lost - paternal chromsomes are double - 46 chromosomes all male.

→ No fetus and trophoblast heavily invading

31
Q

What is the pathophysiology of a partial molar pregnancy?

A

69 chromosomes - maternal and paternal but 2 sets of paternal

→ Some fetal tissue but trophoblast heavily invading

High levels bHCG

32
Q

Loss of maternal chromosome 15 with duplication of paternal chromosome is called…

Loss of paternal chromosome 15 with duplication of maternal chromosome is called…

A

Angelman Syndrome

Prader-Willi Syndrome