Where is the placenta
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
period
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
forget there's plenty of other resources
on the zero to finals website including
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