Table of Contents
- Brain Blood Supply
- Cerebral Artery Anatomy
- Venous Drainage
- Disorders of the Brain Arteries
- Lesson Summary
What blood vessels provide blood supply to the brain? Like all parts of the body, the blood supply of brain tissue is provided by arteries, which are blood vessels that carry oxygenated blood from the heart to different parts of the body. Once the oxygen and nutrients have been obtained from this blood, the deoxygenated blood will be drained by blood vessels called veins.
Such a connection of the two major arteries that supply the brain is important because it serves as a backup system - i.e., in case a problem affects any one of the major arteries, all parts of the brain will continue to receive blood supply from the other artery. The normal rate of cerebral blood flow to the brain is generally 750 mL per minute, which is roughly 15% of the total output of the heart.
There are specific arteries that supply blood to the cerebrum of the brain. They are the anterior, posterior, and middle cerebral arteries. As their names suggest, the anterior cerebral artery supplies blood to the front portion of the cerebrum, the posterior cerebral artery supplies blood to the back of the cerebrum as well as some portions of the sides of the cerebrum, and the middle cerebral artery supplies blood to the middle and sides of the cerebrum.
Specifically, the brain is supplied oxygenated blood by two pairs of arteries including the vertebral arteries and the internal carotid arteries. As they reach the brain, their arteries branch off and their terminal branches anastomose, or connect, to create a structure known as the Circle of Willis, which is located on the underside of the brain. The arterial branches that supply different parts of the brain arise from this Circle of Willis.
The internal carotid artery branches off into a network of multiple arteries. It originates from the spinal cord at the level of the fourth vertebrae in the neck region. The internal carotid arteries move upward from the neck region to the cranium through the temporal bone in the cerebrum. The pulse can be taken from the internal carotid artery since blood pulsates through there from the heart. There is also an external carotid artery that branches off at the same point as the internal carotid artery. The external carotid artery supplies blood to the face and neck rather than the brain. The branches of the internal carotid artery are below.
The anterior cerebral artery branches from the internal carotid artery and are also part of the Circle of Willis. This cerebral artery is located toward the front of the brain, hence the name, since anterior means front. There are two main arteries that branch from the main anterior cerebral artery. They supply blood to the middle section of the frontal lobe, the upper, middle sections of the parietal lobe of the brain, and to deep portions of the brain. The anterior cerebral artery is broken down into five segments.
The posterior cerebral artery is the artery that comes from the basilar artery. It branches off to give rise to the posterior choroidal artery, posterior communicating artery, and calcine artery. The posterior cerebral artery supplies blood to the back portions of the brain, since posterior means back, such as the occipital lobe and the back parts of the temporal lobes of the brain. There are four segments to the posterior cerebral artery.
While the brain needs blood to function, there are many substances that would be harmful to the brain that it does not need to gain access to it. The blood brain barrier, or BBB is the structure of endothelial cells within the walls of the arteries that determine which substances from the blood can pass into the brain and which ones cannot pass into the brain. It prevents hydrophilic substances and harmful pathogens from entering the fluid around the brain and spinal cord known as cerebrospinal fluid. Cerebrospinal fluid must be sterile and free of detrimental substances in order to allow the brain and nerves to function normally. The blood-brain barrier allows some substances such as glucose, amino acids, and ions that are needed for functioning to cross the barrier from the blood into the brain.
The venous drainage system of the brain begins with the dural venous sinuses. These are drainage holes that are located within the meninges of the brain. They are responsible for draining blood from the brain, spinal cord, face, and scalp. There are a total of eleven dural venous sinuses and they end up dumping the blood that they have collected into the internal jugular vein. The internal jugular vein is the largest vein in the neck that is responsible for draining blood from the entire head region. It ultimately leads to the superior vena cava. There are two internal jugular veins, one on each side of the neck.
The arteries of the brain function normally most of the time, but there are instances where something can go wrong within the arteries and this spells trouble for the brain and the body as a whole. These disorders are discussed below.
Arteries carry blood to different parts of the body and veins bring blood back to the heart. The rate of blood flow to the brain is 750 mL per minute. The brain receives oxygen through the vertebral arteries and internal carotid arteries. The pulse can be taken by feeling on the side of the neck to touch the internal carotid artery. The different arteries of the brain anastomose, which is connecting, at the site of the Circle of Willis. The internal carotid artery contains the following:
The blood-brain barrier, or BBB, is comprised of the endothelial cells that determine which substances enter the brain from the blood. It keeps the fluid around the brain and spinal cord known as cerebrospinal fluid sterile from invading toxins. Brain cancers are difficult to treat because the medications have a hard time passing the blood-brain barrier. Venous drainage from the brain is accomplished through the dural venous sinuses which drain into the internal jugular vein. Disorders of the brain include a stroke, which is when there is an interruption in blood flow to the brain, an aneurysm, which is a bulging in the artery, and traumatic brain injury, which is when there is an injury to the brain.
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There are two arteries that supply blood to the brain. One is the internal carotid artery and the other is the vertebral artery. Both of these arteries branch off into a network of arteries that work together to supply blood to the brain.
A blocked artery in the brain is a stroke. It is called an ischemic stroke when a stroke occurs due to a blockage in one of the arteries of the brain. This is in contrast to a hemorrhagic stroke which is when there is a leaking of one of the arteries in the brain.
Brain arteries are the vertebral arteries and the internal carotid arteries. The different arteries of the brain connect together in a structure known as the Circle of Willis.
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