1. Internal Carotid Arteries

Internal carotid arteries consist of the left internal carotid artery and the right internal carotid artery which run along the inner side of the front of the neck towards the brain.

Internal carotid arteries originate from the common carotid arteries at the level of the thyroid cartilage. Common carotid arteries generate both internal and external carotid arteries.

• What Happens If There Is a Stroke in Internal Carotid Arteries?

A stroke affecting the internal carotid arteries will result in a lack of blood supply to the areas controlling vision, speech, and sensations.

2. Vertebral Arteries

Vertebral arteries consist of the left vertebral artery and the right vertebral artery which run along the back of the neck toward the skull where they both merge to form the basilar artery.

The basilary artery is responsible for the supply of blood to the brainstem, cerebellum, the posterior part of the brain, and also the upper part of the spinal cord.

Vertebral arteries are originated from the subclavian arteries that originate from the aortic arch (left subclavian artery) and the brachiocephalic artery (right subclavian artery).

• What Happens If There Is a Stroke in Vertebral Arteries?

A stroke affecting the vertebral arteries will result in a lack of blood supply to the areas controlling muscle movements and coordination, speech and vision, and alertness.

3. What Is the Circle of Willis?

The circle of Willis is formed by the meeting of the internal carotid arteries and the vertebral arteries at the base of the brain.

From the circle of Willis 3 major arteries are originated: the anterior cerebral artery (ACA), the middle cerebral artery (MCA), and the posterior cerebral artery (PCA).

4. What Does the Anterior Cerebral Artery Supply?

The anterior cerebral arteries (left and right) are connected by the anterior communicating artery and supply blood to the frontal lobes and the superior parietal lobes of the brain through their cortical and central branches.

The cortical branches of the anterior cerebral arteries supply blood to:

• The olfactory cortex, gyrus rectus and medial orbital gyrus through its orbitofrontal branches
• The corpus callosum, the cingulate gyrus, the medial frontal gyrus, and the paracentral lobule through its frontal lobe branches
• The praecuneus through its parietal branches. 

The central branches of the anterior cerebral arteries supply blood to the deep cerebral structures such as the rostrum of the corpus callosum and surrounding structures.

• What Happens If There Is a Stroke in Anterior Cerebral Arteries?

A stroke affecting the anterior cerebral arteries will result in a lack of blood supply to the areas controlling thinking, decision-making, and muscle strength of the legs [2].

5. What Does the Middle Cerebral Artery Supply?

The middle cerebral artery supplies blood to the cerebrum, the anterior temporal lobes, and the insular cortices through their cortical and central branches.

The cortical branches of the middle cerebral artery supply blood to the orbital, frontal, temporal, and parietal parts of the cerebral cortex.

The central branches of the middle cerebral artery supply blood to the deep structures of the brain such as the basal ganglia, and the caudate nucleus.

• What Happens If There Is a Stroke in Middle Cerebral Arteries?

A stroke affecting the middle cerebral arteries will result in the following symptoms:

· Hemiplegia (Paralysis on one side of the body)

· Blindness (the left or right side)

· Language problems, such as impairment in the ability to form words and sentences or understanding what others are saying.

· Changes in sensation

6. What Does the Posterior Cerebral Artery Supply?

The posterior cerebral artery supplies blood to the occipital lobes at the back of the brain and the posteromedial temporal lobes through their cortical and central branches.

The cortical branches include the thalamoperforating arteries, the thalamogeniculate arteries, the posterior choroidal arteries.

• The thalamoperforating arteries supply blood to the midbrain and the thalamus.
• The thalamogeniculate arteries supply medial and lateral geniculate nucleus and the pulvinar nuclei of the thalamus.
• The posterior choroidal arteries supply blood to the choroid plexus and the posterior part of the thalamus.

The central branches include the temporal branches, the occipital branches, the parieto-occipital artery, and the calcarine artery.

• The temporal branches supply blood to the uncus, and the parahippocampal, medial and lateral occipitotemporal gyri.
• The occipital branches supply blood to the cuneus, lingual gyrus, and posterolateral surface of the occipital lobe.
• The parieto-occipital artery supplies blood to the precuneus and cuneus.
• The calcarine artery supplies blood to the cuneus and lingual gyrus.

• What Happens If There Is a Stroke in Posterior Cerebral Arteries?

A stroke affecting the anterior cerebral arteries will result in a lack of blood supply to the areas controlling vision [3].

7. What Is a Stroke?

A stroke is the interruption of blood supply to the brain causing the death of brain cells. The longer is the lack of blood supply the more damage is caused to the brain.

The causes are associated with any event that causes the interruption of blood supply to the brain. The main causes are the following:

• Ischemic stroke which is due to a blockage of an artery (e.g., Atherosclerosis).
• Hemorrhagic stroke due to the bursting of an artery causing hemorrhagie that leads to significant loss of blood.

A transient ischemic attack is when the interruption of the blood supply is temporary.

Conclusion

The brain is supplied by the internal carotid arteries and the vertebral arteries that form the circle of Willis where the anterior cerebral arteries, middle cerebral arteries, and posterior cerebral arteries branch out to supply the different parts of the brain.

A stroke in one of these arteries or its branches will have specific symptoms that are associated with the control of specific functions within the body.

There are certain conditions that increase the risk of stroke including diabetes, hypertension (high blood pressure), high cholesterol levels in the blood, and irregular heartbeats.

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