hello all this is dr. Alsup again and in this session we are going to focus on the arteries we
want you to be able to identify in the cranial cavity and brain session so mostly focused on
the arteries of the brain we will focus on an inferior view of the brain for much of this
discussion because it really affords the best view of these structures so let's get started
the brain is going to be supplied by two main arterial sources and the vertebral arteries are
going to be one of these you can see the vertebral arteries here closely associated with the medulla
I am trying to outline the vertebral arteries and it's not uncommon for the caliber or the
size between the right and the left of very like you can see here so you see this one is a little
bit larger than what you have on this other side so it's not uncommon to see that recall that the
vertebral artery is a branch of the first part of the subclavian artery so it has to ace in quite a
ways to reach the brain through the transverse foramina of cervical vertebrae c1 through c 6
and eventually up through the foramen magnum it has three branches in this area that we want you
to be able to identify or conceptually understand where they would be located let's start with the
anterior spinal artery which you can see right here it's this little bitty artery right here
you can see it receives contributions from both vertebral arteries and it will kind of run down
the midline of the medulla so this is the medulla right here which will eventually transition into
the spinal cord that relationship is really the most telling and it will be considerably
smaller than the vertebral artery so if you see something right down the midline of medulla you
know you're likely looking at the anterior spinal artery next let's try to locate the posterior
inferior cerebellar artery and I'm sorry I went a little bit further than I meant to but we can kind
of make that up so let's go back to so there's that anterior spinal artery and let's find the
posterior inferior cerebellar arteries and that is really a mouthful so we like to abbreviate
things that are a mouthful and you'll often hear this referred to as pica or pica it is going to
be the branch of the vertebral arteries that's a little bit on the larger side particularly in
comparison to the anterior spinal artery you can see these coming off transversely from
the vertebral arteries it really has a close relationship with the accessory nerve that
you can see right about here ich as a day sends through this region pocket typically gives off
the posterior spinal artery even though this these can be a direct branch of the vertebral artery so
you can't see it coming off a pike ax or from the vertebral arteries directly now you are not going
to be able to see the posterior spinal artery very well in this view you would have to see it
a little bit more on the posterior view but you can see them peeking out right about here ich
and one thing I want you to note there are two typically to supposed to your spinal arteries
whereas there is typically just one anterior spinal artery which you can see here okay back
to this image that I erroneously move towards so we can see that in anterior spinal artery
but let's move up to the basilar artery now this is formed by the coalescence of those vertebral
arteries and where they join together then we're getting into the basilar so I'm outlining that
right here so basilar is right here it's gonna run down the midline of the pons and this is your
pons right here and the arteries name the basilar or the basilar because of its close relationship
to the cranial base there are three branches of the basilar artery that we want you to be able to
identify the most proximal of these is going to be the anterior inferior cerebellar artery so a
pretty similar name to what we have with the the pica you sometimes will see this referred to as
and this is fairly close to where the basilar artery becomes the basilar artery so not too
far from the vertebral arteries you see these small branches here these are typically smaller
than pica the pica arteries but will often form anastomosis with pica and you
see it's fairly closely associated to the abducens nerve or cranial nerve 6 next we have the superior
cerebellar artery and I always will kind of slip up because you have cerebellar and cerebral in
this area well this is going to be the superior cerebral you can see that over here in this region
that's going a little bit further down here so those are the superior excuse-me cerebellar so
I told you I'd mess it up so superior cerebellar it's typically the smaller one it's going to be a
little bit more on the posterior portion and then the largest and the last branch of the basilar or
the base lower will be the posterior cerebral so cerebral not cerebellar so here is your posterior
cerebral here and the posterior cerebral here so you can see it's a slightly larger artery branch
in terms of caliber than the superior cerebellar before we move on I want to note the cranial nerve
here that is between these two arteries you can see it right here and right here that is going to
be cranial nerve free or your oculomotor nerve the close relationship between the oculomotor
nerve and the superior cerebellar and the posterior cerebral is a very important anatomical
relationship I can almost promise you that will show up in some form of assessment so make sure
that you can identify that in relationship to these two arteries all right now we are on to
the other major arterial supplier to the brain and this is the internal carotid artery or your
AICA so one of those terminal branches of the common carotid artery I recall that this was
the branch I had no branches in the neck it saved all it's fun for the brain and the skull region
and so there gonna be a lot of branches that we need to know here this artery is going to be the
major supplier of the forebrain region of the brain now when you're looking at this view of
the brain so this inferior view the internal carotid artery are had to be cut in order to
remove the brain from the skull so you'll often only see these paired fairly large cut arteries
in this general area but it really quickly is only this long in this region before it branches
into its two terminal branches and the largest of the terminal branches is going to be the middle
cerebral so here's your middle cerebral over here it is gonna look almost like the continuation of
the internal carotid artery because it's about the same size in terms of caliber it's going
to be easiest to locate in the lateral fissure of the brain so it's often easiest to see when
the temporal lobes of the brain are moved out of the way which is what is happening here so
these were moved out of the way in order to have a better view of the middle cerebral arteries
the smaller terminal branches are going to be the anterior cerebral so you can see those here
these arteries are going to loop around the optic chiasm so here is your optic chiasm right here
and it's going to move anterior lateral to the longitudinal fissure so you can see it traveling
up in this region so not only is are these the ant anterior cerebral so are these so this is where it
continues additionally you can see this tiniest of branches between the two anterior cerebrals and
this will be the anterior communicating artery so we'll come back to that one in a moment the last
branch of the internal carotid artery wants you to identify as another small artery and it's another
communicating artery and these are the posterior communicating so posterior communicating so you
can see that one here and it's a little bit harder to see right here but here's
your other posterior communicating this artery you will see connecting the posterior cerebral
artery with either the internal carotid artery directly like you see in this particular image
or it can meet with the middle cerebral artery a little more laterally but the point is that it is
allowing for some communication between branches of the vertebral artery and branches of the of the
internal carotid artery or a branch of internal carotid lastly I want to talk about the cerebral
arterial circle which you will most typically hear referred to as the Circle of Willis this is
composed of branches we have already discussed and identified but I just want to review these in the
general area as this is such an important clinical area the cerebral arterial circle is a prominent
anastomosis of branches of the internal carotid and the vertebral arteries and this circle will
be right around I mean it's kind of trace about where the Circle of Willis is located so it's
going to be right in that region so it's going around the infundibulum or that pituitary stalk
area as well as the optic chiasm so it's going around those regions it's going to be composed
of the anterior cerebral arteries connected by that little anterior communicating so that's going
to allow that communication between those two arteries as well as the posterior communicating
artery which allow for communication between the posterior cerebral artery and the internal
carotid artery so that's where you get that dress communication between vertebral artery
and internal carotid so you allow that flow from two very different blood flow sources and that
can be important in terms of if there's any kind of disruption of flow it will allow blood to get
to regions throughout the brain all right so I believe that is about as much fun as we can have
with the arteries of the brain it has been fun finally getting to see the internal carotid artery
have some branches it's not just that external carotid artery as always if after you review and
you find areas of confusion please feel free to contact me with any questions and have a great day