well in this video we're going to
introduce the fascinating idea of the
circulation of the blood and just before
we start we're thinking about the heart
in the middle here now when you're
thinking about Anatomy you're always
looking at someone else so that's the
left side and that's the right side
because we're looking at someone else's
heart so here we have the left side of
the heart and here we have the right
side of the heart and the heart's got
two Chambers the Atria at the top and
the vent course at the bottom and we're
going to start this circulator restoring
out now I'm going to start here in this
bottom chamber on the right hand side so
that is the right ventricle so here we
have blood in the right
ventricle and I'm coloring this in blue
which of course is ridiculous because
blood is not blue but for drawing
diagrams of the blood we normally do red
for the oxygenated blood the blood which
is high in oxygen and blue for the blood
which which is lower in oxygen that's
why I've drawn it blue now if the blood
is low in oxygen where does it need to
go to get
oxygenated well of course it needs to go
here up to the lungs so first of all the
blood needs to go up to the
lungs so this ventricle will contract
ejecting the blood up into the lungs and
the blood will
profuse circulate through the
lungs and as that happens it will be
progressively
oxygenated we'll get high levels of
oxygen so we start drawing that as a red
color so the blood is going to go to the
lungs relatively low in oxygen and it's
going to return from the lungs
relatively high in
oxygen now the vessel
there between the right ventricle and
the lungs that vessel there is the
pulmonary artery carrying blood to the
lungs
pulmonary means to do with the lungs and
this is the pulmonary veins there's
actually four of these in real life
carrying the blood from the lungs are
back to the heart but we're noticing now
that the blood is fully oxygenated so
we're drawing it as bright red and that
blood's going to go into the left
atrium and from there it's going to go
through there's actually a pair of
valves there it's going to go through to
the left
ventricle the left ventricle then the
left ventricle is going to contract and
that's going to eject all the blood out
into the aort this major blood vessel so
all the blood from the left side of the
heart goes to the
aort and maybe you can see already that
it was the right side of the heart
that's pumping blood to the
lungs so we call the right side of the
heart the lung pump the lung pump and as
we're about to see it's the left side of
the heart that's pumping blood to the
body so all of the blood that goes to
the body body apart from the lungs which
we don't count as the body although it
is part of the body obviously that's the
lung circulation and we're now talking
about the body circulation all the blood
to the body circulation what's sometimes
called the sematic circulation goes via
the
aorta now this is diagrammatic it's not
anatomically accurate but it represents
what's going on so we want the blood to
go from the aort and it'll go through
various
arteries and it will go through what is
called the brachial artery and this is
what takes blood into the arms so the
blood is going to go into the arms and
in the arms the cells there are working
away so they need the oxygen so they're
going to take up the oxygen and they're
going to reduce the amount of oxygen in
the blood and they're going to put in
some carbon dioxide so once the blood is
draining from the arms in this case via
the calic
vein then that blood is going to be de
deoxygenated and it's going to be
blue then and that's going to go back to
the heart via a vessel called the
superior vena now all the top half of
the body is drained by the superior
venne Cava so that blood is going to go
back through the superior venne Cava and
can you see it's going back to the heart
it's going back to the what chamber is
that it's the right side isn't it and
it's the atrium so that's the right
atrium so can you see the blood that's
going from the right atrium through to
the right ventricle is is relatively
oxygenated blood so that kind of
describes the circulation to the
arms but then other branches from the
aort will take blood up to the through
the neck the big arteries that you can
feel pulsating in your neck are the
koted
arteries and they're going to take Blood
to the Head including of course the all
important
brain and again the blood's going to
profuse through that and as it goes
through it's going to give up some of
its oxygen it's going to collect some
carbon dioxide and then it's going to
drain and the big veins you can see in
the side of your neck are the jugular
veins the jugular veins and the jugular
veins are going to drain back and again
because it's the top half of the body
they're going to drain back into the
superior venina Cava these great big
cavernous ve veins that take the blood
back to the
heart so that's all very good for the
top half of the body but of course we
need a blood supply on the bottom half
of the body as well
and so blood's going to go
down and we can see that blood's going
to go to the liver this vital organ in
the top right hand side of the abdomen
just under the right ribs there and the
blood The Vessel taking blood there is
the hepatic artery taking blood to the
liver and the blood's going to go
through the
liver as the blood goes through the
liver of course it's going to be
deoxygenated the liver's actually very
metabolically active lots of
biochemistry going on in the
liver that's going to drain from the
liver via the hepatic
veins and the hepatic veins are going to
drain into the the big vein drain in the
bottom half of the body is the inferior
venne caver into the inferior venne Cava
which also drains back into the right
atrium before going back into the right
ventricle to go to the lungs to get
oxygenated
again now complications arise already
now this tube here represents the gut or
what we call the gastrointestinal tract
basically that's everything from your
esophagus to your anus from your food
pipe all the way through your stomach
your um small intestine large intestine
is represented by that tube there and of
course it's living tissue it's going to
need a blood supply and uh some of that
is going via the
mesenteric arter here taking blood to
the gastrointestinal tract which is
absolutely brilliant that gets
oxygenated
there and of course as the blood goes
through it's going to give up the oxygen
pick up the carbon dioxide so it's going
to change to what we draw as blue blood
which of course is partly deoxygenated
blood now it's a bit of a complication
here because can you see there's
something called the hepatic portal vein
now a portal vein is a vein
which connects two things without going
back via the main veins so so the portal
vein actually starts in capillaries and
ends in
capillaries so blood is going to go from
the gastrointestinal tract and it's not
going to drain back into the inferior
vena cava straight away until it's gone
through the
liver it has to go through the liver
first so the blood from the gut does not
drain straight back into the inferior
vava it drains into the liver first why
is
that why do you
think well in the gastrointestinal tract
there's all sorts of
bacteria you've probably heard of these
the good bacteria the
microbiome but they produce waste
products of metabolism and if they went
straight back into the blood they'd make
you feel sick all the time so they go to
the liver first and the liver is this
biochemical processing Factory it breaks
down the the waste products from the
bacteria
so the blood here in the TIC portal vein
is going to contain waste products from
bacteria that's going to be cleaned out
by the liver and the clean blood is
going to go from the liver in the TIC
veins back into the inferior Reena Cav
so it's going to clean it all out if
that wasn't the case you'd be feeling
sick right now and hopefully you're not
because your liver is doing its job and
as well as that foods that are absorbed
from the gastrointestinal tract go to
the liver for processing before they go
back into into the systemic circulation
again this the systemic circulation the
Sy C circulation for the whole body all
the systems of the body these are all
the systems of the
body now blood's going to carry
on down through the lower part of
the uh going down in the aorta to the um
abdominal aorta and some blood is going
to go to the kidneys in fact a lot of
blood goes to the kidneys because the
kidneys are where the blood is filtered
and cleaned and the urine's produced so
as the blood goes through the kidneys
again it's going to become partly
deoxygenated the blood as it goes
through the kidneys is also going to be
cleaned and the waste products from the
blood are going to be excreted into the
urine so anything that the kidneys don't
want kept in the blood go into the urine
anything the kidneys want kept in the
blood they keep in the blood and they
will send back to VI the renal
veins back into the inferior venne CA
which is taking blood
back all the way up all the way up there
all the way up there back into the right
atrium to go to the right ventricle to
go back to the lungs to get
oxygenated and of course you want plenty
of blood going to your legs so you can
run and move around so blood is going to
go further down and the main vessel
taking blood into
the legs of the femoral arteries so
they're taking blood to the legs
as the blood goes through the legs it's
going to give up some of its
oxygen collect carbon dioxide then the
blood is going to drain from the legs
via the femoral veins the femoral veins
are going to drain back up into the
abdominal cavity into the inferior venne
Cava all the way back up to the right
side of the heart the right atrium to go
to the right ventricle to go to the
lungs to get oxygenated it again so
quite amazing really we've got this
whole circulatory system picking up
oxygen getting rid of carbon dioxide in
the lungs taking oxygen to the tissues
taking waste carbon dioxide from the
tissues all circulating around all the
time the
brilliant complicated but in essence
really such a simple circulatory
system so that is the s of the
circulatory
system