Understanding the Placenta

hi this is tom from zero to finance comm

I wanted to make a video today on the

function of the placenta and trying to

understand exactly how it works to

support the fetus while it's growing so

firstly we got to take a basic look at

the placenta we all know that the baby

comes along with an umbilical cord and

down that cord you have two umbilical

arteries and they carry deoxygenated

blood away from the baby and then you

have one umbilical vein and that carries

all the good oxygenated blood that's

full of nutrients away from the placenta

and into the baby

inside the placenta you have a bit of a

complex network of arteries and veins

but they're quite simple once you get

your head around them first of all you

have the maternal vein and artery inside

the placenta and these veins and

arteries feed into something called the

interval of space and what this is is

basically pools of maternal blood a form

sort of like a lake in which lots of

maternal blood is collected just sitting

there waiting to interact with the fetal

blood now you have the umbilical

arteries in the umbilical veins that

penetrate and form a sort of tree like

structure within the interval space so

inside those pools of blood and the

maternal blood and fetal blood don't

actually mix but they come in very close

contact across a thin membrane and

that's known as the placental membrane

so across this placental membrane lots

of things can transfer or diffuse from

the maternal blood into the fetal blood

and vice versa and it's this process of

diffusion that forms much of the

function of the placenta

let's look at the first function of the

placenta and that's the respiratory

function though because the baby can't

actually breathe it's in a big bath of

amniotic fluid it needs to rely on the

placenta to basically act like a pair of

lungs so what does it do well firstly

oxygen needs to transfer from the

maternal blood into the fetal blood and

the way it does this is fetal hemoglobin

has a higher affinity for oxygen than

maternal hemoglobin what this means is

if you put a molecule of maternal or

adult hemoglobin next to a molecule

fetal hemoglobin oxygen will actively

transfer from the maternal hemoglobin to

the fetal hemoglobin just think of the

fetal hemoglobin as being more sticky

for the oxygen more attractive for the

oxygen the second respiratory function

is that the carbon dioxide that's

present in the fetal blood all of this

waste carbon dioxide that's generated by

the fetus simply diffuses across the

placental membrane from the fetal blood

into this pool of maternal blood that

way the baby can get rid of a lot of the

carbon dioxide that it's created

the next function is an excretion

function and you can think of this as

the placenta acting a bit like a kidney

that you'd find in an adult so what it

does is it balances out a lot of the

chemicals and molecules that need to be

balanced in the blood

things like bicarbonate hydrogen ions

lactic acid urea and creatinine they can

all diffuse across the placental

membrane and balance out the baby's

blood in the same way that a kidney

would do in an adult the next function

of the placenta would be the nutrition

function so the baby can't actually eat

any food while it's in the womb so it

relies on the mum to eat and create

carbohydrates and micronutrients that

circulate around the mums blood and then

these diffuse across the placental

membrane into the fetal blood and

provide the fetus with oxygen and

vitamins and micronutrients that it

needs to grow this is one reason it's so

important that the mom doesn't become

nutrient deficient in say iron or folate

or b12 during her pregnancy so if we

find that she's deficient we'd

supplement her with these

the fourth function of the placenta is

the immunity function now antibodies

that the mother has created her immunity

to infections that she's picked up in

the past those antibodies can actually

cross the placental membrane and into

the fetus and this is really good news

because it protects the baby during the

pregnancy from any viruses or bugs that

the mum might pick up and also protects

the baby shortly after birth so a really

good example of this would be of

recurrent genital herpes where the mum

has had genital herpes several times in

the past she'll have i GG antibodies to

that virus so when she gives birth

naturally even if she has active genital

herpes they won't be passed to the baby

because all of those antibodies will

have cross the placenta and will be

circulating inside the fetus ready to

protect it whenever it comes into

contact with that virus in the newborn


and the final function of the placenta

that we need to mention is the endocrine

function this is where the placental

tissue itself actually creates hormones

that help to maintain the pregnancy the

first hormone that we should mention is

human chorionic gonadotropin or HCG this

hormone is secreted increasing levels

throughout the pregnancy by the cells of

the placenta and what it does is it

helps to maintain the corpus luteum

until the placenta takes over producing

other hormones that maintain the

pregnancy the next home when the

placenta produces is East region and

this is important to make everything

soft and supple all of the tissues of

the uterus and pelvis so that they can

get stretched during the pregnancy and

during birth and delivery and the final

hormone that their placenta produces is

progesterone and it produces

progesterone from about five weeks

onwards and the whole point of

progesterone is to maintain the

pregnancy and keep the uterus nice and

relaxed and to keep the endometrium nice

and healthy and well profused so that

it's got a great blood supply for the

BLA Center and for the fetus and that

pretty much sums up the respiratory

excretion nutrition immunity and

endocrine functions of the placenta so

thanks for watching I hope you found

this video helpful if you did don't

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