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If you’re learning cerebral circulation, what you should not do is blindly memorize a diagram like this. Instead, you need to understand the big picture that this is really two circulation systems: an anterior cerebral circulation and a posterior cerebral circulation, with a few backup arteries that communicate between these systems, which forms the circle of Willis. So, in this video, I’m going to clearly map out those two systems. Then, we’ll add in the communicating
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arteries, and finally, the smaller arteries that branch out to different regions of the brain, and we’ll look at some great three-dimensional views of the brain as well. In other words, we’re going to learn this in a way that you can finally wrap your brain around. So, let’s jump to the whiteboard and get started. So, let’s start first with the posterior cerebral circulation. In the posterior cerebral circulation, we have the vertebral arteries, which are going
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to be bringing blood into this posterior cerebral circulation. There will be separate arteries, the internal carotid arteries, that are going to bring blood into the anterior cerebral circulation. But these vertebral arteries that go up through the transverse foramina of the cervical vertebrae are going to bring blood into the posterior cerebral circulation. And those two vertebral arteries
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will converge and form what’s called the basilar artery, which is at the base of the brainstem. It kind of runs up along the medulla here and the pons before it’s going to separate right in here. The two vertebrals converge into the basilar. Now, before we go on and add more onto this, I want to take a look at the three-dimensional view of this so we can see where this blood is coming from. So, here we have our 3D model. I’m going to zoom in on this. And first, we want to
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take a look at the branches of the aorta. And here we’ve got the subclavian, and on the other side, we’ve got the subclavian right there. And a branch off of the subclavian that we want to look at here is the vertebral artery. The vertebral artery, we can see it right in here. I know that’s the vertebral artery because it’s going to go up through here and pass through the transverse foramina of the cervical vertebrae. It’s going to pass through a transverse foramen
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right there and right there and right there. Notice, interestingly, that it doesn’t go through the transverse foramen of C7. Actually, it’s just going to go through those foramina of C6 all the way up through C1 right here. Sorry, C1 would be right there. And it’s going to pass through those, and then it’s going to come medially, and then it’s going to go through there. It’s getting a little bit hard to see, but if I zoom in on it right here, we can see it comes up through here
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and it’s going to converge right there into the basilar artery. So, these are the two vertebral arteries converging into the basilar artery. And you notice it’s going to come up through the foramen magnum, which is that big hole in the base of the skull that the spinal cord goes through as well. So blood comes in through the vertebral arteries. It converges in the basilar artery. There’s a lot of other branches that come off of this, but I’m not going to go over those yet. I’m
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going to go over the general overview of the two circulation systems and connect them together, and then we’ll go back through at the end and add on the other branches here. But the main branch we want to add onto this at the end of that basilar artery is the posterior cerebral artery, and we label that PCA for short as its abbreviation. Now there’s three cerebral arteries. There’s the posterior cerebral artery, which we have labeled here. There’ll be an anterior cerebral artery,
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of course. So if we have posterior, we must have anterior, and there’ll also be a middle cerebral artery. The middle and the anterior will both be part of the anterior cerebral circulation system. And we can see that posterior cerebral artery. It’s going to branch off. There’ll be a left and a right branch. And then it’s going to branch even further, and it’s going to be supplying blood mainly to the posterior part of the cerebrum, like the occipital lobe, for example. These other
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branches here are going to provide blood to the cerebellum and the parts of the brainstem right here and some other areas. Now to visualize this a little bit better, I’ve got these two diagrams which are amazing. I didn’t create these diagrams, but I’ll cite those in the description below. These are really nice diagrams to show us what regions of the brain are supplied by which cerebral arteries. So everything in blue here is going to be supplied by the posterior cerebral
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arteries. You can see it’s a lot of the occipital lobe right here. It’s going to be the posterior part of the parietal lobe a little bit right there, and then it’s going to be the inferior part of the temporal lobe right in here. And we can see from our midsagittal view right here, there’s that occipital lobe and then some parts of the inner parts of the brain right here as well, the
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corpus callosum, for example. But again, these are general areas. If you’re a neurosurgeon, you might not be wanting to watch this particular video. You might need something that goes a little bit more specific and in depth, but that’s the general area supplied by the posterior cerebral artery. So, that’s our posterior cerebral circulation. Next, we’re going to look at our anterior cerebral
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circulation. And for that, we’re going to have a different area that’s bringing blood into this cerebral circulation. For the anterior side, we have blood coming in through the internal carotid arteries. Of course, we have the common carotid arteries, and those will branch into the internal and the external carotids. So this internal carotid is bringing that blood in. Let’s take a look real quick three-dimensionally to see where this blood is coming from. So let’s zoom in again
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on our 3D model here, and we’re going to take a look at the carotid arteries this time. So last time we looked at the vertebral arteries, which branched off of the subclavian. For the anterior side, we’re looking at the carotid arteries. So we have got the left carotid artery right here. We got the right carotid artery right here, which is branching off of the brachiocephalic trunk. And those carotid arteries are going to branch into the external carotid artery right here
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and the internal carotid artery right there. So we’re interested in the internal carotid artery. So we’re going to follow that internal carotid artery up right here. And if I zoom in on this, we can see that going through a little hole in the base of the skull. That’s going to be the carotid canal. That’s where that blood is coming into the anterior cerebral circulation side. So that full path there is aorta to the common carotid artery. That’ll branch off into the
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external and the internal carotid artery. And the internal carotid artery is going to pass through that carotid canal in the base of the skull. And that’s where we’re at in our anterior cerebral circulation diagram. So blood is going to come in through the internal carotid artery, and then it’s going to have a couple arteries it’ll branch into. One of those is the middle cerebral artery.
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So we see that middle cerebral artery right here. This is on the right side. Of course, we have it on the left side as well. And then that’s going to branch off a bunch, and we’ll label a couple of those branches later on. But I want you to notice something. That middle cerebral artery, it’s going to head to the sides, or it’s going to go laterally on either side of the brain. So the middle cerebral artery, even though normally we think of middle and medial kind of going together,
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in this case, it doesn’t. The middle here means it’s not anterior and not posterior, but it’s middle when we go front to back, but it’s actually going to run laterally, and it’s going to supply the lateral parts of the cerebrum with blood. We’ll take a look at those other diagrams with the regions in just a second. So there’s the middle cerebral artery, and then we have the anterior cerebral artery right here. That’s going to be the other branch.
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So the internal carotid branches into the middle cerebral and the anterior cerebral. The anterior cerebral is kind of unique. It’s going to go anteriorly. It’s going to run up this way, and it’s going to stay medial. If you look at all this, it’s not going lateral here. It’s staying very medial. And what it’s going to do is it’s going to come up right here. And I’ve got it shown a little bit. It’s kind of hard to represent on a two-dimensional diagram here. But this part right
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here is going to run through that longitudinal fissure that separates the two hemispheres of the brain. And it’s going to go up and wrap around the corpus callosum. So we can see that if I hold up my brain model here from Anatomy Warehouse, and that anterior cerebral artery is going to come up right here and, like I said, it’s going to wrap around the corpus callosum. So it wraps around
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it right there, and there are all these other branches that’ll be coming up off of it, supplying this medial part of the cerebrum with blood. Of course, on the lateral side, that’s going to be mainly not the anterior cerebral artery, but that lateral side will be the middle cerebral artery. And just to clarify on this diagram right here, these two do not connect to each other. Those are two separate anterior cerebral arteries that are wrapping around the corpus callosum. So here,
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let’s take a look at those two diagrams. We can see those regions, and in yellow here we have the anterior cerebral artery. So you can see on this midsagittal view it’s really supplying most of this with blood on this medial side. We got the frontal lobe, the parietal lobe back here, a little bit of the occipital lobe. And then if you look at the lateral view, we don’t really, you know, most of this lateral section is supplied by the middle cerebral artery. So that’s going to
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be part of the temporal lobe, the superior part of the temporal lobe, some of the parietal lobe, a little bit of the frontal lobe right here. But if you look at the medial side, it’s going to be all that anterior cerebral artery. So in general, not getting super specific here, the posterior cerebral artery is going to be that occipital lobe, the inferior part of the temporal lobe, mainly the back of the brain. The anterior cerebral artery is going to be mostly the
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medial part, so right in here. And then the middle cerebral artery is going to be the lateral part of the brain. All right, let’s jump back to here. At this point, we have two regions of cerebral circulation. We got the anterior cerebral and the posterior cerebral. We really have three systems right now because the anterior cerebral has not been connected yet. There’s going to be the left
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anterior cerebral, there’s the right anterior cerebral, and we haven’t drawn in any connections there. And then we have the posterior cerebral, no connections there. And our brains, I think, would work perfectly fine like this. The problem is if we do have an obstruction of these arteries, which are getting smaller and supplying arguably our most important organ with blood, a blockage
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there would cause a stroke, which is going to be basically fatal in what we have right now. So our brains have some redundancy built in through what we call the communicating arteries, and it’s going to connect these different circulations together. So let’s add in those communicating arteries here. The first one here is a single artery called the anterior communicating artery. Of course, we have the anterior. We’re going to have a posterior communicating artery. And that anterior
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communicating artery, or ACOM for short, is going to connect the right anterior cerebral circulation with the left anterior cerebral circulation. By the way, for the abbreviations here, just notice that the communicating arteries we call ACOM. We’ll call the posterior PCOM. And then the cerebral arteries, we use the CA: ACA, MCA, PCA. But don’t get this confused. The anterior communicating artery we do not label ACA. ACA would be anterior cerebral arteries. Those get
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the preference here for the ACA and MCA and PCA. And then the communicating we call this ACOM and PCOM. So again, for this anterior side, we’ve got blood coming in through the internal carotid. It’s going to branch into the middle cerebral and the anterior cerebral, which will wrap up around the corpus callosum. And then we have the anterior communicating artery, which communicates between the right and left side. And next we have the posterior communicating artery. That’s going
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to communicate between the anterior side and the posterior side. And we actually have two of those, one on the left and one on the right. Those will connect the posterior cerebral artery right there to that internal carotid artery kind of right before it branches off into the middle and anterior cerebral arteries. So on our posterior side we have the vertebral arteries converge into
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the basilar artery that’s going to branch into the two posterior cerebral arteries, and each of those is going to have a little branch here which is the posterior communicating artery, which connects up to that internal carotid right before it branches into the anterior and middle cerebral arteries. And again, the reason for that is let’s say that we had a blockage here. Let’s say we have it in
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the anterior cerebral artery in this A1 section. That’s this first section before it hits the ACOM. Let’s say we had a blockage right there. If we did not have any communicating arteries, blood would flow in through the internal carotid, it would start up this branch, and it would block, and basically we’d have a huge section of our brain not getting blood. It’d be very, very bad. But because we have this communicating artery, we can take some alternate routes. If we
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have blockages in this circle of Willis right here, so let’s say that we have this blockage there. Well, the blood that’s coming in through the left internal carotid could go up through the anterior cerebral A1 right there and then through the anterior communicating artery, and it could bypass this blockage because it’s got this extra little bridge there in the ACOM. And so what this does, these two communicating arteries, their main function then is to help us avoid deadly
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ischemic strokes or hemorrhagic strokes here by building in a little bit of redundancy in the cerebral circulation. And at this point, you can see it’s formed this kind of unique little circular pattern of arteries here, and that’s what we call the circle of Willis. Let’s identify those circle of Willis arteries real quick when we talk about that circle of Willis. We have the ACOM, anterior communicating artery. Then we have the ACA, the anterior cerebral artery, but just the
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A1 section. This would be A1 right here. A2 would be right here, and it goes on from there. We have the posterior communicating artery, which forms part of that circle. Most of the things I looked up when I was researching this did not include the internal carotid as part of the circle, although it does need to pass through part of that internal carotid right there. It’s not passing up and down to form the circle. And finally, the posterior cerebral artery, specifically the P1
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section, which is right in there. If you combine all those together, so ACOM, ACA, PCOM, PCA, PCA, PCOM, ACA, back up to the ACOM right there, that’s forming that circle of Willis. All right, so let’s go back to this diagram right here. And now that we have our overview, our general structure of all of these, this might be a good time to pause the video and see if you can label all of these so far. But what I’m going to do now is take a look at the smaller branches
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that branch out mostly off this posterior cerebral circulation side, but a little bit of the anterior as well. So we’re going to add in some additional arteries here. The first one that I want to add in is the anterior spinal artery. Kind of unique. It’s going to branch off of the vertebral arteries right here. It branches off of either side but immediately converges into one anterior spinal
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artery, and it’s going to run down the anterior part of the spinal cord and provide blood to that anterior region of the spinal cord. So a pretty interesting branch, I think, because blood has just traveled up and now it’s traveling back down to supply the anterior spinal cord. Up next, let’s take a look at some branches that are going to supply blood to the cerebellum. So the first one
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here we’ve got the posterior inferior cerebellar artery. A lot of directional terms going on there. But the way that I want you to think about this is we’re going to have one superior cerebellar artery and we’ve got two inferior cerebellar arteries. And if we have two inferior cerebellar arteries, we’ve got to differentiate between those two. And that’s why we add in the posterior. So the two inferior, we’ve got a posterior and we’ll have an anterior inferior cerebellar artery.
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You can see that branch is going to branch off of the vertebral arteries on either side. It’s going to go posterior and supply this inferior but also posterior part of the cerebellum right here. And then up here we’ve got that anterior inferior cerebellar artery. Notice those don’t branch off of the vertebral arteries, but they branch off of the basilar artery. And they’re going to go over here and they’re going to supply still the inferior side, but more on this anterior
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part of the inferior side of the cerebellum. Of course, if we have inferior cerebellar arteries, we have to have a superior cerebellar artery. And that’s going to branch off of the basilar artery way at the top, the distal side of this, right before it gets to the posterior cerebral artery. So this is going to be the superior cerebellar artery. In my diagram, it disappears a little bit behind the pons, but it’s going to come up here and supply this superior part of the cerebellum
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with blood. Later on in the video, we’ll look at some 3D views of all of these arteries here.
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That might help you piece some of this together and see it three-dimensionally later on in the video. So the two inferior arteries for the cerebellum and the superior cerebellar artery branches off right here. Now we’ve got five more branches you can see right here between those. So that first one’s going to be the labyrinthine artery, and that’s called the labyrinthine artery because it’s going to go to the inner ear, to the bony labyrinth of your inner ear. So that’s where
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the blood supply for that inner ear comes from, and that’s why we call it the labyrinthine. And then just distal to the labyrinthine branches, we’re going to have four branches which are going to be the pontine branches. And those, we’ve got these four short branches that are going directly to the pons, which is where the basilar artery already is. So those pontine arteries are going to be several arteries branching off of the basilar artery to supply the pons with blood. All
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right, let’s label a few more branches on the anterior side. On this middle cerebral artery, we can see a couple branches in this diagram. One is the lateral orbital frontal branch of the middle cerebral artery, and so that’s going to come up into this region right here. It’s lateral. The medial orbital frontal branch will be in here, and it’ll be a branch off of the anterior cerebral artery. And orbital frontal, orbit of course is referring to the eye region
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right in here, and it’s going to be frontal, so it goes to the front of the brain as well as to the orbit area right there. And then we have the prefrontal branch of the middle cerebral artery. And so this is going to be prefrontal, meaning it’s a little bit anterior to the frontal region. We have that branch. Of course, as this goes up the central sulcus right here, there’s going to be more and more branches of that middle cerebral artery. They’re just not going to
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be labeled on my diagram here. And next, I want to label that medial orbital frontal branch of the anterior cerebral artery. And so in my diagram, it would be this one right here. Now again, I want to say that it’s really hard to represent some of these parts of the anterior cerebral artery specifically on a two-dimensional diagram because this actually goes up and wraps around the corpus
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callosum. These are three-dimensional structures here. So this is about where the medial orbital frontal branch of the ACA will be. But again, if you want to get more in depth with these branches, you really need to look at 3D models to see where this is all located or a bunch of different 2D representations to see these. A medial orbital frontal branch, lateral orbital frontal branch, prefrontal branch of the MCA. And then one more I want to label just because at a certain point
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that anterior cerebral artery, once it’s wrapped around the corpus callosum, we start calling it the pericallosal artery instead of the anterior cerebral artery. And of course, pericallosal just means around the callosum, corpus callosum. Now let’s do a quick three-dimensional tour of all of this using our models from anatomy.app. And then after that, I’ll give you a blank diagram so you can practice labeling these yourself. So here we have a nice three-dimensional view of all of
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this. We’ve got the cerebellum back here. We’ve got the brainstem. There’s the pituitary gland. We can see the circle wraps around the pituitary stalk right there with the pituitary gland. And we’ve got the spinal cord here at the bottom going down. So let’s map all this circulation out again using this three-dimensional diagram. We’ve got the vertebral arteries right here and right there
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converging into the basilar artery, which is going all the way up here, which is going to branch off into the posterior cerebral arteries right here. We’ve got a bunch of other branches coming off of there. We’ve got the anterior spinal artery, which is going to come down here and supply blood to the anterior side of the spinal cord. We’ve got the posterior inferior cerebellar artery,
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which is going to come back here. Here you can see that branching off, providing blood to all of this region right here of the cerebellum. And then up here we’ve got the anterior inferior cerebellar artery, which is going to come around here and provide blood to this region of the cerebellum, the anterior side but still inferior. And then of course up here we’ve got this branch which is going to be the superior cerebellar artery, and that’s going to bring blood back over here
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and supply this superior surface of the cerebellum with blood. Here we’ve got those pontine arteries, those little arteries branching off of the basilar artery providing the pons with blood. And then up here we can see the circle of Willis. And so we just had the posterior cerebral arteries. Here we have the posterior communicating arteries on the right and left side. And then right in here we have the end of the internal carotid artery where blood is coming into the anterior
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cerebral circulation here. And here we have the middle cerebral artery branching off, and that’s going to go to remember those lateral sides of the brain. And then here branching off is the anterior cerebral artery. We can see it coming down and then forward. That’s going to wrap up around the corpus callosum. And then right there we’ve got the anterior communicating artery. And of course,
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all of this is going to form that circle of Willis that we see there. And if we look at this, we see that coming this way. That’s going to wrap up around the corpus callosum. I’ve got another view that shows that. So here we have that midsagittal view. And if we zoom in right here, we can see this is the middle cerebral artery, and we’ve got that anterior cerebral artery coming up through here. And we can see it branching off. It’s going to come up this way, and it’s going
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to wrap all the way around the corpus callosum with lots of branches coming off of it, supplying the medial part of our cerebrum with blood. In this diagram as well, we can see right there, it’s cut in half there, but that’s going to be that anterior communicating artery as well. And if we follow that middle cerebral artery around here, we can see all these branches that are supplying this lateral side with blood here. Those are all going to be branches off of that middle cerebral
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artery. Now, of course, if you’re trying to learn this stuff really well, it’s good to take a blank diagram and see if you can label all these. So pause the video, see if you can label all of those branches and arteries of the cerebral circulation. And while you’re here, if you want to make sure that you’re learning really effectively and not wasting your time using ineffective strategies, I’ve got a free anatomy and physiology survival guide linked in the description for that and
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probably a link popping up on the screen. It just gives you the best study strategies and warns you against what not to do that a lot of people do whenever they’re studying anatomy and physiology. All right, so here are those labels back so you can check how you did. A few more things. Thank you to my top Patreons and YouTube channel members. Thank you for supporting the channel. You
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are awesome. Appreciate you all being here. And if you’re learning anatomy physiology, like I said, that free survival guide, I’ve got that linked here. I’ve got comprehensive guides for each A&P system. I’ve got study cards that you can use to learn all this stuff. And of course, I’ve got my Memory Lab course. If you’re struggling with learning A&P or really any life science class, I built this course because I’ve seen so many people struggle with using ineffective
23:32
strategies and thinking they’re not cut out to be a doctor or a nurse or whatever it is that you’re studying for. That program includes all the study cards and unit guides and other resources and direct feedback from me on your learning process. So, if you want to learn faster, score higher, and stop forgetting all the things that you’re learning for your class, then I’d love to see you in the program. Hopefully this video has been helpful for you learning
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cerebral circulation. Here’s another video that the YouTube algorithm thinks that you might want to watch for me to continue your learning. And I will see you in the next video. All right, bye!
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