Even though the brain takes up only 2% of our entire body weight, it requires a hefty 20% of its blood. The blood system of the brain carries oxygen, glucose, and nutrients, collects neuronal waste, distributes hormones, and spreads heat to all the structures of the body.
To be more specific, the brain blood supply network carries oxygen, carbohydrates, amino acids, fats, hormones, and vitamins into the brain, while the blood vessels comprising it carry carbon dioxide, ammonia, lactate, and some hormones, out of the brain.
All the brain’s information processing centers depend on the proper and sufficient supply of blood and nutrients. Without oxygen and glucose carried by the blood supply system, the brain becomes dysfunctional and the deterioration of its functions can lead to loss of consciousness.
How Does Blood Circulate to the Brain?
The human brain receives its supply of blood mainly from the blood pumped by the brain via the left and right internal carotid arteries that run up each side of the neck, as well as from the two vertebral arteries that run alongside the spinal cord. When two of the vertebral arteries join at the lower side of the skull, they form the basilar artery.
The internal carotid arteries supply the cerebrum with nutrients and blood, while branches of the vertebral and basilar artery supply both the cerebellum and the brain stem.
Together with the two internal carotid arteries and the other blood vessels of the brain, the basal artery forms a full anastomotic ring of arteries, labeled as The Circle of Willis.
Arterial Supply of Blood to the Brain
The vast network of blood vessels stretches out both on the surface and deep within the brain. Both the nerves and the blood vessels enter the brain through the foramina in the skull.
What Are the Foramina in the Skull?
There are 21 small openings, i.e. foramina on the human skull. They serve as passages for the cranial nerves, blood vessels, and arteries of the face that further connect to the tissues of one part of the body to another.
The foramina of the skull are of great importance because of the fact that many of the most important blood vessels and nerves pass through them in order to supply the brain and to carry information to and from the brain, which is a highly complex process.
Which Arteries Comprise the Vast Network of Blood Vessels That Supplies Blood to the Brain?
The blood supplying network of the brain comprises a large number of arteries that provide nutrition and oxygen to all areas of the cerebral cortex. The list includes the following structures:
- Circle of Willis
- Anterior Cerebral Artery
- Right Middle Cerebral Artery
- Left Middle Cerebral Artery
- Basilar Artery
- Anterior Communicating Artery
- External Carotid Arteries
- Posterior Cerebral Artery
- Vertebral Arteries
- Common Carotid Arteries
- Internal Carotid Arteries
Arterial Supply to the Spinal Cord
Circle of Willis
The Circle of Willis is the location where three pairs of main arteries, the anterior, middle, and posterior cerebral arteries stem from.
This ring of arteries surrounds the base of the brain and provides multiple pathways for oxygen and nutrition supplies to all regions of the brain. If a pathway becomes blocked, the blood can be redirected from another pathway so that the brain is never left without a blood supply, i.e. oxygen and nutrition.
This network of oxygen-supplying arteries progressively branches into smaller arteries and arterioles that run along the surface until they reach the brain tissue in order to supply blood to the dedicated areas of the brain.
Anterior Cerebral Artery of the Brain
The anterior cerebral artery of the brain is one of the arteries that supply oxygen, glucose, and nutrition to the midline areas of the frontal and parietal lobes. It stems from the internal carotid artery, runs above the optic nerve, and along the curve of the corpus callosum.
Right Middle Cerebral Artery of the Brain
This is the largest branch of the internal carotid artery. The lateral surfaces of the temporal and parietal lobes, as well as a part of the frontal lobe, receive their nutrients via the right middle cerebral artery of the brain.
This includes oxygen and glucose supply for some of the most vital information processing centers of the brain, such as the primary motor and sensory areas of the face, throat, hand, and arm, and the areas for speech in the dominant hemisphere of the brain.
Left Middle Cerebral Artery of the Brain
The left middle cerebral artery of the brain also rises from the internal carotid artery. This artery is most often affected in stroke.
Basilar Artery of the Brain
This artery is formed by joining two vertebral arteries. It’s a part of both the blood supply system of the brain and the central nervous system.
This artery is the main vessel that conducts oxygen, glucose, and nutrition through the blood to the brainstem, cerebellum, thalamus, and the medial portions of the temporal and parietal lobes of the brain.
Anterior Communicating Artery of the Brain
The anterior communicating artery of the brain joins the two anterior cerebral arteries and supplies blood to the medial and superior parts of the frontal lobe, as well as to the anterior parietal lobe.
Тhis artery arises from the internal carotid artery almost at a right angle. It reaches deeply into the brain so it can supply the most distant areas of the basal ganglia. It also supports the conduct of oxygen, glucose, and nutrient supply to the medial and superior parts of the frontal lobe, and the anterior parietal lobe.
External Carotid Arteries of the Brain
The external carotid artery is the major blood supplying vessel in the brain. It stems from the common carotid artery, and then branches into an external and internal carotid artery, in order to supply the neck and the face with blood.
Posterior Cerebral Artery of the Brain
The posterior cerebral artery of the brain is actually comprised of a pair of arteries responsible for supplying blood to the occipital lobe, thalamus, the inferior part of the temporal lobe, as well as a portion of the back part of the brain.
Vertebral Arteries of the Brain
These arteries enter the brain through the foramen magnum, i.e. the largest opening on the skull. Each of the VA of the brain generates the following arteries:
- Meningeal branch – An arterial branch that is responsible for supplying blood to a sheet of dura mater, labeled as falx cerebelli.
- Anterior and posterior spinal arteries – These arteries run along the entire length of the spinal cord and supply it with oxygen, glucose, and nutrition.
- Posterior inferior cerebellar artery – An artery that supplies the cerebellum with blood.
Common Carotid Arteries of the Brain
The common carotid arteries of the brain are divided into:
- External carotid arteries, and
- Internal carotid arteries.
Internal Carotid Arteries of the Brain
The internal carotid arteries are located at the level of the fourth cervical vertebrae and enter the brain via the carotid canal of the temporal bone. Each of the ICA generates the following arteries:
- Ophthalmic artery – An artery that supplies the orbital area structures.
- Posterior communicating artery – It functions as a connecting vessel in the Circle of Willis.
- Anterior choroidal artery – Supplies oxygen, glucose, and nutrients to the brain areas responsible for motor control and vision.
- Anterior cerebral artery – An artery that supplies blood to a part of the cerebrum.
Arterial Supply to the Spinal Cord of the Brain
A single anterior spinal artery (ASA) and two posterior spinal arteries (PSA) comprise the main blood supply system of the spinal cord. This artery is formed by the vertebral arteries that stem from the subclavian arteries.
Which Disorders Occur When the Arterial Blood Supply System to the Brain is Dysfunctional?
When the blood flow in the brain is obstructed, the neuronal cells do not receive sufficient amounts of oxygen, glucose, and nutrition. Namely, if they narrow, rupture, if the blood vessels become clogged, or if there are clots in them, the blood flow won’t be strong enough to reach the brain and its processing areas.
This, in turn, can result in the death of the brain cells, disrupting the functions in all areas of the brain responsible for the processing of the received sensory information.
If the obstruction of the blood flow in the brain lasts too long, this can lead to a brain stroke, and other severe medical conditions, such as:
- Thrombosis
- Embolism
- Hypoperfusion
- Hemorrhage
- Intracerebral Aneurysms
- Spinal Cord Infarction
- Brain Ischemia
- Cerebral Hypoxia
- Vascular Dementia
The resulting medical conditions from the dysfunctional blood supply system of the brain are usually accompanied by the following symptoms: numbness or a tingling feeling, partial or complete loss of vision or double vision, confusion, slurred speech, etc.
How to Increase Blood Flow in the Brain?
Increased blood flow in the brain improves its processing functions since its structures receive sufficient amounts of both oxygen and nutrients.
The blood flow in the brain can be increased by including more Vitamin D in an individual’s nutrition, doing physical exercises more often, drinking less caffeinated drinks (like coffee, tea, or cola), limiting salt intake, avoiding sugar, etc.
Fun Facts
Did you know?
- The aorta is the largest artery in the brain-blood supply system. It’s the main high-pressure blood-vessel that is connected to the left ventricle of the heart. The aorta extends throughout the body via a widely spread network of smaller arteries. The arteries’ smaller branches are called arterioles and capillaries.
- Capillaries are the smallest and most numerous of the blood vessels, carrying blood between arteries and veins. Capillaries link small arteries (arterioles) to veins (venules).
- When the brain is left only 4-8 minutes without oxygen supply, the consequent result is severe brain damage or even death.
- The brain is the structure with priority in the blood supply system. Namely, even if any other system needs more blood, the body would take care that the brain is the first structure to receive an unlimited and unobstructed supply of nutrients via the blood supply system.
- If the supply of blood to the brain structures stops, the brain cells will die out.
- Distal blood circulation refers to the blood supplied to the areas of the brain which are most distant from the central body.
- Anastomosis is the connection between two tubular structures, like the blood vessels.
- Dura mater is the outermost membrane that envelops the brain.
- The word carotid (meaning: a carotid artery) originates from the Greek word karotis, which can be translated as ‘deep sleep’. This is due to the fact that pressure to the carotid arteries triggers sleepiness in animals.
- The subclavian arteries are a pair of large arteries that supply blood to the thorax, head, neck, shoulders, and arms.