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BIOL3044 > Maternal environment influences on placental structure and function > Flashcards

Maternal environment influences on placental structure and function Flashcards

1
Q

LO

A
  • Overview of placental structure at term
  • Overview of placental function
  • The placenta and fetal growth
  • Structural adaptation
  • Functional adaptation
  • Summary
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2
Q

Placental structure in humans is dfferent to other species, what are the basic overall structures to the placenta?

A
  • Placental function is dependent on structure
  • Left picture is what the foetus would see in the womb
  • Blood brought down umbilical cord
  • Amniotic and chorionic membrane present (the foetal membrane)
  • Right photo shows the placenta embedded in the womb
  • Maternal blood also inside of the placenta

comprised of both maternal and embryonic tissue

The chorion is the embryonic-derived portion of the placenta and is composed of fetal blood vessels and trophoblasts which are organised into chorionic villi

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3
Q

Tell me more about the placental structure, including the lobules

A
  • Placenta is made of 20-40 lobules
  • These are the functional units
  • Have their own maternal and foetal blood supply

maternal blood supply: from one or two spiral arteries/ lobules

Foetal blood supply: from one or two villous trees per lobule

  • these lobules are where nutrients are gained from waste exchange
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4
Q

Tell me about the 4 components that work together to make the placenta work as a functional unit

A

Syncytiotrophoblast: the outer layer of the villi, these are cells that have fused together to form the syncytium, no cell gaps just one cell

Capillaries: bring foetal blood up to the branches

Stroma: Connective tissues

Villi: vascular projections that increase the surface area. Also, exchange of oxygen and carbon dioxide

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5
Q

What is the placental barrier

A
  • No cell-cell junctions
  • Not known how FA get across the endothelium as they aren’t water soluble
  • Syncytiotrophoblast is the main barrier which things need to be transported across
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6
Q

What does the placenta form from?

Tell me about this

A

The placenta forms from the embryonic trophectoderm

Trophectoderm cells form the outer layer of the embryo

These cells help the embryo implant and invade the maternal decidua

Then they form placental villi

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7
Q

Impaired placental function could be inititated where?

A

In the embryo

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8
Q

What can affect the number of embryonic trophectoderm cells?

A

Periconceptual diet

This also then affects subsequent placental development

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9
Q

What may IVF alter?

A

Epigenetic regulation in the placenta

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10
Q

In mice seminal fluid may affect what?

A

endometrial environment, placental growth and offspring outcome

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11
Q

The placenta functioning in the correct way is essential for what?

Why is this the case?

A

Foetal growth

  • All the nutrients in the foetus recieves across the placenta
  • As the foetus grows the placeta needs to be able to work harder and harder
  • If the placenta does not work properly the foetus cannot grow properly

Poor foetal growth is associated with disease in later life

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12
Q

What are the main roles of the placenta?

A
  • Barrier (protects the foetus)
  • Nutrient transport (feeds to foetus)
  • Placental hormones that alter maternal physiology (helps the mother adapt to support pregnancy)
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13
Q

What is the first hormone that is secreted in pregnancy?

A

hCG

Human Chorionic gonadotropin

This is a hormone produced during pregnancy

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14
Q

How do gasses and nutrients cross the placenta?

A
  • O2 and CO2 are lipid soluble and can just diffuse across the membrane and therefore rapidly across the placenta
  • Glucose needs a transporter as are not lipid soluble and can’t just cross the membrane
  • The thing that limits gas transport is flow as this maintains the gradients
  • Gradients is what drives the transfer and if the blood flow isn’t fast enough, on either maternal or foetal, then the gradient will go away
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15
Q

Tell me about the transfers from maternal blood to foetal blood

What membranes are involved, and what is transported?

A
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16
Q

What might limit the placental function?

What factors may lead to each of the reasons?

A

Reduced maternal blood flow

Preeclampsia, maternal cardiovascular disease

Too few villi

Not enough branching in 2nd trimester

Too few transports proteins

Gene/protein expression

Increased diffusion distance

Poor development in third trimester

Too little foetal blood flow

17
Q

What can change placental function in the short term?

A

regulation of transporter levels

regulation of uterine or umbilical blood flow

potential for therapeutic intervention?

18
Q

What can cause long term changes in placental function across gestation?

A
  • change in size/structure
  • epigenetic change/regulation
  • more difficult to treat, focus on prevention! i.e., through diet, exercise, healthy lifestyles etc. man and woman
19
Q

What can cause longer term changes in placental function across generations?

A
  • There is huge inter-species diversity in placental structure
  • Selective pressures drive changes in the placenta
  • Placental function is important for reproductive fitness!
  • Prevention is always better than cure
20
Q

What does the placenta require for growth?

A
21
Q

What does the foetus need for growth?

A

Nutrient supply to match growth potential

But not always

  • If the mother does not have a lot of food growing fast is not the best option
  • And if the foetus grows too big it cannot be delivered easily

Ideally the placenta would match transport with foetal demand but also consider mothers’ ability to provide

22
Q

What factors may affect placental function?

A
  • Food intake
  • Stress
  • Exercise
  • Body composition
  • Preeclampsia
  • Diabetes
  • Altitude
  • Smoking
23
Q

There are structural adaptations with the villi in response to what?

A

Signals in the maternal environment

Intrauterine growth restriction, or IUGR, is when a baby in the womb (a fetus) does not grow as expected. The baby is not as big as would be expected for the stage of the mother’s pregnancy. This timing is known as an unborn baby’s “gestational age.”

24
Q

What is affected at high altitudes?

A

The placental adaptation has to adaptor at high altitude as there is low oxygen

At high altitude O2 is low which will affect the maternal-fetal gradient

So how does the placenta overcome this in people who live at high altitude?

We will look at studies from two different high-altitude populations

25
Q

What was the placental adaptation in the following study…

Study 1: placentas at 760m and 2800m in Kirghizstan

A
26
Q

What was the placental adaptation in the following study…

Study 2: placentas at 500m and 3600m in Bolivia

A
27
Q

Adaptations at high altitudes…

A

Adaptation to altitude

  • Studies do not always agree
  • Different placental adaptations may achieve the same outcomes
  • How a placenta adapts may depend on ethnic origin (e.g., genetics)
  • Placental adaptations have also been found in smokers, diabetics, anaemia, pre-eclampsia
28
Q

Changes in oxygen levels can affect what?

A

Cell growth

29
Q

Low oxygen could affect placental development at multiple stages, tell me the effects

A
  • the number of cells in embryonic trophectoderm
  • slower implantation
  • altered growth
30
Q

Structural changes are likely to persist throughout pregnancy, so the earlier they start the longer they will last.

With functional adaptations, what are they 1st and 2nd in response to?

A

They are 1st in response to maternal signals

They are 2nd in response to foetal signals

31
Q

Glucose transporter levels may be set when?

Tell me about this

A

In early gestation

Placentas from insulin dependent diabetic mothers have increased GLUT1

  • Elevated glucose in early gestation?

Placentas from gestational diabetic mothers have normal GLUT1

  • Glucose levels become elevated later in gestation

Are GLUT1 levels programmed by glucose levels in early pregnancy?

32
Q

What mechansims links early pregnancy glucose and placental GLUT1 at term?

A
  • Not short-term regulation
  • Unlikely to be structural change or size
  • Possibly epigenetic? (suggests a window of susceptibility)
  • In mice, maternal obesity has been shown to alter epigenetic regulation in the placenta
33
Q

Summary

A

BIOL3044 (11 decks)

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