so what we're going to talk about in
this video is we're going to talk about
the two feeder pathways into the Circle
of Willis because there's gonna be two
important vessels that are gonna be
feeding this Circle of Willis one is
gonna be up here which is called the
internal carotid artery okay
and this is going to be feeding into the
circus at this part the other part that
we're going to discuss is going to be
down here and this is going to be the
vertebral artery that's going to feed
into the back part of the Circle of
Willis so what we're going to do is
we're going to start here with the
actual vertebral arteries and work our
way up through the diagram annotating
each individual vessel and then we'll
come back and we'll talk about certain
diseases that can be associated when
there is occlusions of these vessels or
maybe being aneurysms okay one more
thing is just before we keep going I
want to give you guys a little bit of
orientation of this diagram so that we
understand what we're looking at so when
you see here this is gonna be the right
cerebral hemisphere right cerebellum
this over here is gonna be the left
cerebral hemisphere left cerebellum okay
and when we're looking at this actual
Circle of Willis we're looking at it
from an inferior view okay thus this
annotation right there alright so now
let's go ahead and get started here so
first things first we have to have these
arteries right here so you see these
arteries here on the side these bad boys
right there are gonna be called
your vertebral arteries you know they're
actually going to be supplied from the
subclavian arteries
now the vertebral arteries are really
interesting because they actually run up
through these holes in the actual
cervical vertebrae and they call these
holes the transverse foramina okay but
these arteries right here that are
actually moving up through those
transverse foramina are called the
vertebral
arteries
now the vertebral arteries what they do
is to actually run up through the
transverse foramina of the cervical
vertebra and then after that they
actually proceed before going up into
the frame and Magnum they run through
what's called the suboccipital triangle
and when they come up through the
foramen magnum they're gonna move up
like this okay so now they're going to
be moving up through the foramen magnum
as such as they move upwards they give
off branches here right this branch
right here that you're gonna see coming
off it's a special branch very very
important one this bad boy right here is
gonna be called the posterior inferior
cerebellar artery so we call this the
posterior inferior cerebellar artery
okay
so that is going to be this artery right
here
okay so posterior cerebellar artery in
the same way this one over here I'm just
gonna denote it as pi Co P I see a post
here in fear cerebellar artery that is
going to be this guy right there now off
of the posterior inferior cerebellar
arteries comes these other little
branches okay so this branch right here
in this branch right here these guys
right here are called your posterior so
they're called the posterior spinal
arteries okay so again this one right
here is called your posterior spinal
artery okay
so yeah the vertebral arteries moving up
as they move up they give off a
posterior inferior cerebellar artery and
then these posterior inferior several
orders will give off these little
branches here called the post here
spinal arteries now the vertebral
arteries will continue to move up move
up and give off another branch so
they're going to give off a branch here
give off a branch here these guys will
fuse together and form an artery that
moves all the way down the spinal cord
this is a really important one this guy
right there it's specifically called the
anterior spinal artery so this guy right
here is called the anterior spinal
artery
okay so again vertebral arteries post
here in fear cerebral arteries off of
that is the posterior spinal arteries as
the vertebral arteries move up they give
off branches that fuse together and form
the anterior spinal arteries now that
after that here's where it gets really
really important the vertebral arteries
will come together and fuse when they
fuse they'll move up as this big big
vessel right here in the middle this bad
boy here that's moving all the way up
the thick part here this guy here is
called the bacilli artery okay that's
this guy right there so you know we have
the bacilli artery which is this guy
moving all the way up here but as we
come up here and form the basilar artery
there's another branch that comes off
all right
there's another branch that comes right
off here this is another really
important one they're all really
important because any type of occlusion
of these vessels can cause some serious
serious diseases and syndromes this one
right here that comes off the basilar
artery here at the base this is called
the anterior inferior cerebellar artery
so this is called the anterior inferior
cerebellar
artery so now as we're coming up here
again we said we have the vertebral
arteries vertebral arteries are gonna do
what they're gonna give off posterior
cerebral arteries they give off
posterior spinal arteries then we're
gonna move up here so we're moving up
through the medulla right so this is the
medulla here we're gonna come together
fuse these vertebral arteries right
before we fuse they give off branches
here at the medulla which is called the
anterior spinal artery that's an
important one because it does supply the
pyramids here and that moves down
throughout the spinal cord then
vertebral arteries come together fuse
and make the basilar artery at the base
of that pasilla artery we have this
anterior inferior cerebellar artery
formed here at the level of the pons now
we have this next one here and this is
called the labyrinthine arteries okay so
these two suckers right here are called
your labyrinth labyrinthine arteries
okay so that's my labyrinthine artery
and this is another labyrinthine artery
okay or you can call them internal
acoustic arteries okay then as we
continue upwards throughout the pons
we're gonna have all of these guys right
here these are all pontine branches of
the vasila artery so all of this is
going to be upon tyne branches okay
so we have all of these guys up here up
to the actual level of the pons now so
again we had midbrain
we have pons I'm sorry we have medulla
pons and then we're to have the midbrain
up here now as we move up past the
pontine branches we give off another
branch this branch here will supply the
top of the cerebellum and this sucker
right here is going to be called the
superior cerebellar arteries so this
right here is called my superior
cerebellar arteries okay so that's gonna
be this guy right there
as well as this one over here now as we
continue to move up at the level of this
midbrain here your
see that the bacilli artery is going to
feed into the posterior part of this
circle we call this circle the Circle of
Willis now as the as the basilar artery
feeds in it feeds into this part right
here this is actually this whole thing
here from this part to this part is our
posterior cerebral artery okay
so this whole thing here is the
posterior cerebral artery but there's
two parts of it or two segments if you
will so let's say from here to here this
segment is called the p1 segment of the
posterior cerebral artery and then from
that point here to this point here this
is the p2 segment of the posterior
cerebral arteries okay so again these
arteries right here this whole one over
here if we were to write it down this
whole thing here is going to be called B
posterior cerebral arteries okay and
again this segment here would be p1 this
one here would be p2 all right sweet
deal so we fill this posterior part of
the Circle of Willis well now after that
look where else it can go now the blood
can move into this next collateral
channel because you know the brain the
actual arteries of the brain are a great
example of an arterial anastomosis which
are just basically alternative or
collateral channels for blood to flow
through and it's a beautiful thing
so now as this bacilli artery feeds into
the posterior cerebral artery p1 segment
it can then go up into these suckers
over here on the sides these guys here
on the sides this one here and this one
here this is called the posterior
communicating artery x' so this is
called the posterior communicating
artery okay same thing on that side this
would be the posterior communicating
artery now here's where it gets really
cool remember I told you that the
posterior part of the Circle of Willis
is formed by the vertebral basilar
system right that feeds into that part a
good 20% of the blood is from the
vertebral basilar system the remaining
80% of the blood feeding into the Circle
of Willis is gonna be through these
puppies right here okay these guys right
here that are really important right
here and right here this is your right
and left internal carotid artery but
again I'm just gonna write here internal
carotid artery okay
now the internal carotid artery when it
feeds into this it gives off a branch
first you see this sucker right here
this guy right here is called the
ophthalmic artery okay we call this the
ophthalmic artery now I like to say the
edge because I'm not good at spelling so
that helps me out so that is the H this
guy right here is called the op thalmic
artery okay so this right there is the
ophthalmic artery then if we continue
through the internal carotid artery it's
gonna come out here and it's gonna give
off this branch over here this is one of
the big branches coming off of the
internal carotid artery that guy right
there is called the middle cerebral
artery so from here to here this entire
thing here is called the middle
cerebral artery but why is this
important because off of the middle
cerebral artery comes some really
important branches what are some of
these branches coming off the middle
cerebral artery well the first one is
this sucker right here that guy right
there is called the anterior choroidal
artery so this right here is called the
anterior choroidal artery okay
that's coming off of this middle
cerebral artery another branches that
are really important and they're going
to the lenticular Valente form nucleus
as well as some of the other structures
around that is called the lenticular
Schreyer re so all of these guys right
here these are specifically called the
lenticular striate arteries okay and
again the most important part of this
one as this goes is gonna go to the
actual internal capsule as well as the
linty form nucleus with a Globus Politis
and the put'em in okay then after that
here's where it gets really cool okay
internal carotid artery fed into this
circle wills right well then it gives
off this branch that moves from here all
the way here so watch this from this
point here and I'm gonna come all the
way down to about this point right here
so from this follow it all the way up
that entire thing is the anterior
cerebral artery so what does this
structure here that we said we said from
here all the way to here is referred to
as the anterior cerebral artery now just
like the posterior cerebral artery it's
split into segments from this point here
to about this point here they call this
the a1 segment of the anterior cerebral
artery and then from this point here to
this point here this is called the
whose segment of the anterior cerebral
artery so same thing over here a two
segment and a one segment of the
anterior cerebral artery okay now
there's this next one right here which
is so important so important because
it's so exposed it's very very affected
in situations like berry aneurysms this
sucker right here is called the anterior
communicating artery so we're gonna
throw this right here and the optic
chiasma so this right here this
structure is called the anterior
communicating
artery okay and again that is the answer
communicating artery right there okay so
now we have covered all of the important
vessels of the Circle of Willis
all right engineers so that pretty much
covers everything that you guys would
need to know about the actual Circle of
Willis so now what we're gonna do is in
the next video we're gonna start talking
about certain types of clinical
implications what can happen if there's
occlusions of these vessels or aneurysm
so in the next video we're gonna talk
about the cerebral ischemic strokes okay
so I hope to see you guys there but guys
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alright engineers as always until next
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[Music]
you