Maternal environment influences on placental structure and function Flashcards
LO
- Overview of placental structure at term
- Overview of placental function
- The placenta and fetal growth
- Structural adaptation
- Functional adaptation
- Summary
Placental structure in humans is dfferent to other species, what are the basic overall structures to the placenta?
- 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
Tell me more about the placental structure, including the lobules
- 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
Tell me about the 4 components that work together to make the placenta work as a functional unit
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
What is the placental barrier
- 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
What does the placenta form from?
Tell me about this
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
Impaired placental function could be inititated where?
In the embryo
What can affect the number of embryonic trophectoderm cells?
Periconceptual diet
This also then affects subsequent placental development
What may IVF alter?
Epigenetic regulation in the placenta
In mice seminal fluid may affect what?
endometrial environment, placental growth and offspring outcome
The placenta functioning in the correct way is essential for what?
Why is this the case?
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
What are the main roles of the placenta?
- Barrier (protects the foetus)
- Nutrient transport (feeds to foetus)
- Placental hormones that alter maternal physiology (helps the mother adapt to support pregnancy)
What is the first hormone that is secreted in pregnancy?
hCG
Human Chorionic gonadotropin
This is a hormone produced during pregnancy
How do gasses and nutrients cross the placenta?
- 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
Tell me about the transfers from maternal blood to foetal blood
What membranes are involved, and what is transported?
What might limit the placental function?
What factors may lead to each of the reasons?
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
What can change placental function in the short term?
regulation of transporter levels
regulation of uterine or umbilical blood flow
potential for therapeutic intervention?
What can cause long term changes in placental function across gestation?
- 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
What can cause longer term changes in placental function across generations?
- 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
What does the placenta require for growth?
What does the foetus need for growth?
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
What factors may affect placental function?
- Food intake
- Stress
- Exercise
- Body composition
- Preeclampsia
- Diabetes
- Altitude
- Smoking
There are structural adaptations with the villi in response to what?
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.”
What is affected at high altitudes?
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
