Brain Blood Supply: Anatomy & Diagrams

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  • 2:13 Internal Carotid Artery
  • 3:45 Anterior Cerebral Artery
  • 4:29 Posterior Cerebral Artery
  • 4:57 Circle of Willis
  • 7:05 Blood Brain Barrier
  • 8:49 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
You'll never look at a shopping mall the same way again once you learn in this lesson how similar it is to your brain. We'll also find out why connections between blood vessels are important and how your brain protects itself against toxic substances in your blood.

Redundant Blood Supply to the Brain

I've got a great idea. We should take a trip to the mall and do some shopping together. If we can't afford to actually buy anything, that's okay. We can at least do some window shopping. As we walk into this very large mall, we see a directory and note that the store we want to go to is located on the second floor of the mall. Since this is a very busy mall with lots of people walking around, the architect of the mall did a very nice job designing several methods for us to get to the second floor. We can either walk up the stairs, take the elevator, or we can use the escalator to make it to the second floor. Why in the world would the architect create more than one way to get up to one floor? It takes quite a bit more money to construct all of this.

But, I think you already know the answer. What if the elevator breaks, the escalator stops working, or the stairs are shut down for repairs? If one or two of those occur, we will always have at least one other option to use in order to get to the second floor. The architect had a lot of foresight in making sure that congestion, in this case because of lots of people, can be relieved through more than one avenue.

Your brain is just as, if not more, special in this sense. Think of the mall as your brain. The people trafficking through the mall carrying money they want to spend in a store are like your red blood cells carrying oxygen to spend in brain cells. The red blood cells must have a way of making it into the mall, making their way around it, up and down, left and right. They do this via channels, like the halls in the mall, called blood vessels. And, like the stairs, elevators, and escalators in the mall, the blood vessels in the brain provide red blood cells more than one option of accessing the same exact point in the brain in case one option isn't working, is too congested, or is completely blocked off.

You'll find out exactly how this works in your brain as we explore the many arteries which supply your brain with blood, how they connect, and what important structures they form.

The Internal Carotid Artery

Your brain has quite a few arteries which supply it with oxygen. There's a reason for this plethora of choice. It's because your brain needs a large amount of oxygen constantly delivered to it in order to not only function on its own, but also to keep the rest of your body functioning as well. If the brain had only one artery supplying it, and it were to get blocked by a clot, then you would die almost instantaneously. This is why having so many ways of getting blood to your brain is critical: if one channel, or vessel, is blocked, there's always at least one other way to get around the blocked passageway.

With this in mind, let's take a look at some of the major arteries supplying your brain with oxygenated blood.

Oxygenated blood is supplied to the brain through major arteries such as the carotid artery
Carotid artery

The most important artery running up the side of your neck is called the common carotid artery. It splits into two branches. One of the branches is called the external carotid artery, which supplies your neck and face with oxygenated blood. The other branch of the common carotid artery, which supplies the brain with oxygenated blood, is the internal carotid artery. The internal carotid artery, again, is a branch of the common carotid artery that supplies the brain with oxygenated blood. Each side of your body, more specifically, each side of your neck and head, has one internal carotid artery supplying blood to the brain. Therefore, you have a grand total of two internal carotid arteries.

The Anterior Cerebral Artery

As the internal carotid artery enters your brain, it gives off a branch called the anterior cerebral artery. The anterior cerebral artery is a branch of the internal carotid artery supplying the anterior, or front, portions of your brain with oxygenated blood. This artery is also important because it provides another avenue by which your brain can be supplied with blood, just in case another passageway is closed off.

In addition, because you have two internal carotid arteries and each one has a branch called the anterior cerebral artery, it should make sense that you have two anterior cerebral arteries as well.

The Posterior Cerebral Artery

Another artery entering your brain is called the the posterior cerebral artery, which supplies the posterior, or structures at the rear of your brain, with oxygenated blood. There is one posterior cerebral artery on each side of your body. Furthermore, each posterior cerebral artery connects to the internal carotid artery on the same side of the brain in order to complete a very special structure in the brain.

The Circle of Willis

By now, you're hopefully dying to find out what this special structure is. The importance of blood supply to your brain explains why there are so many pathways for oxygenated blood. As the internal carotid artery enters your head, we know it gives off a branch to one side called the anterior cerebral artery. This anterior cerebral artery will then connect to the anterior cerebral artery on the other side of the head and, therefore, by extension, to the internal carotid artery on the other side of the head as well. We also know that the posterior cerebral arteries will also connect to the internal carotid artery through a small vessel. This, therefore, completes a circle of connected arteries, located at the base of your brain, which supply the brain with blood, and we call this structure the Circle of Willis.

The Circle of Willis is connected arteries at the base of the brain supplying blood to the brain
Circle of Willis

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