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 if you guys did like this video please hit that like button comment down the comments section please subscribe also if you guys get a chance check out Facebook Instagram maybe in our patreon account alright engineers
as always until next time [Music] you
