- The arterial circle of the brain (Willis) - structure
- Cerebral arterial circle (Willis) - role
- Cerebral arterial circle (Willis) - imaging
- Cerebral arterial circle (Willis) - diseases
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The brain's arterial circle, or Willis' wheel, is a system of several arteries connected to each other. Its basic function is the ability to ensure - even despite the existence of some pathologies within the blood vessels - a constant blood supply to all structures of the brain. What exactly are the elements of the arterial circle of the brain, what diseases may affect the vessels belonging to it, and how can this system of blood vessels be visualized?
The cerebral arterial circle has been present in the human anatomy literature for quite some time. The physician of English origin, Thomas Willis, is believed to be the person who first described this structure. The scientist published a paper on this complex system of arteries in 1664 and it is from his name that another, also used name for this structure, which isWillis arterial circle(circle of Willis) .
The arterial circle of the brain (Willis) - structure
The Willis arterial circle consists of several arteries, which are:
- internal carotid arteries (left and right - both derive from the respective common carotid arteries)
- anterior arteries of the brain (left and right - they are branches of the internal carotid arteries)
- anterior connecting artery (true to its name, it is the connection between the right and left anterior arteries of the brain)
- posterior arteries of the brain (right and left - both originate from the basilar artery, which in turn arises from the junction of two vertebral arteries - left and right)
- posterior connecting arteries (left and right - they are branches of the internal carotid arteries
Only the above-mentioned vessels belong to the arterial circle of the brain. It should be noted here, for example, that despite the fact that other structures - such as the middle arteries of the brain - also supply blood to the elements of the brain, they are definitely not included in the arterial circle.
The above description is a "book" example of the arterial circle of the brain. In fact, it turns out that just such a classic picture of this structure is found in only around 1/3 of people.
The remaining people also have Willis' arterial circle, but with a slightly different structure - possiblethere is e.g. a significant narrowing of one of the posterior arteries from the brain with a simultaneous large widening of the lumen of the posterior connecting artery.
A significant asymmetry between the right and left parts of the arterial circle of the brain is also possible, but also that some vessels - instead of running separately - will be connected with each other (there may be, for example, joining both anterior arteries of the brain into one vessel ).
It also happens that a person does not have an anterior connecting artery, but the opposite is also possible, where the patient has two such vessels.
Cerebral arterial circle (Willis) - role
When you look at the structure of the arterial circle of the brain, you may notice one fact above all: most of the arteries that form them originate from the internal carotid artery. So what's the meaning of Willis's Wheel?
Well, it is classically assumed that this structure is to ensure a constant, uninterrupted supply of arterial blood to all structures belonging to the central nervous system. Why this is so important, probably does not need to be explained more broadly - it is widely known that nerve cells are among those for which the lack of oxygen is the most severe and which, after a short time from the cessation of its regular supply, they simply die.
The arterial circle of the brain can simply prevent such interruptions in the supply of oxygen - when one of its blood vessels stops transporting blood (e.g. due to its sudden, significant narrowing), other vessels belonging to this structure are to take over this task and ensure an uninterrupted supply of blood to all important centers of the nervous system.
Cerebral arterial circle (Willis) - imaging
Research aimed at specifically visualizing the arterial circle of the brain is rarely ordered. However, if there is such a need, then usually angiographic examinations are performed with the administration of a contrast agent (e.g. iodine contrasts). The contrast administered then intravenously leads to an increase in the absorption of X-rays by the blood - after taking a series of X-rays, an accurate image is obtained, allowing for the visualization of both normal and abnormal structures of the arterial circle of the brain.
Cerebral arterial circle (Willis) - diseases
The vessels belonging to Willis' wheel may include, among others, aneurysms, i.e. segmental widening of the lumen of a blood vessel. They are dangerous (especially when they become large) due to the fact that there is a risk of rupture, which may not only result in disturbances in blood flow in the brain, but also in the fact thatit will then lead to a subarachnoid hemorrhage. Most often - because in over 30% of cases - aneurysms within the arterial circle of the brain are found in the anterior connecting artery.
Another problem that may be related to Willis' wheel is ischemic stroke. It can happen when one of its vessels becomes blocked (e.g. by atherosclerotic plaque) and at the same time - despite its function - the arterial circle will not be able to properly supply the area with reduced blood flow with the necessary her delivery.
Another abnormality that may also affect the function of the arterial circle of the brain is the so-called ste alth team. It results from a narrowing of the subclavian artery, so for many people the ste alth syndrome should not affect the cerebral circulation at all - in fact, however, this problem can result in disturbance of the blood supply to the brain.
This possibility comes from the fact that in the stealing syndrome, blood - instead of reaching the brain via the vertebral artery - can flow back into the vessels supplying the upper limb. This phenomenon may be exacerbated when the hand structures require increased blood supply (as is the case, for example, during exercise), and then the patient may develop various neurological symptoms, such as dizziness, visual disturbances or fainting.
About the authorBow. Tomasz NęckiA graduate of medicine at the Medical University of Poznań. An admirer of the Polish sea (most willingly strolling along its shores with headphones in his ears), cats and books. In working with patients, he focuses on always listening to them and spending as much time as they need.