Our brain is a complex organ that governs and coordinates all of the systems that make up our body. But this organ, and the nervous system in general, does not work from nothing: it needs a continuous supply of oxygen and nutrients to function. This contribution will reach you through the blood supply, reaching the different structures through the cerebrovascular system. Within this system we have different veins and arteries, which converge in the circle of Willis
The Willis polygon: description, location and functions
We call the polygon of Willis a heptagonal structure present in the brain. This structure is formed by the union of the different arteries that irrigate the brain, playing an important role in its supply of oxygen and nutrients. It is considered an anastomosis, or interconnection in a network of parts or elements (in this case the arteries) differentiated from each other.
The circle of Willis can be found at the bottom of the brain, surrounding the heptagon that forms structures such as the optic chiasm, the hypothalamus and the pituitary gland. Its structure can vary enormously from one person to another, finding that more than half of the population has a structure of this polygon different from what is considered classic or typical.
The functions carried out by the circle of Willis are of great importance for our survival, since The blood that irrigates much of the brain flows through it Furthermore, we are dealing with the main auxiliary mechanism that allows blood to continue reaching the different regions of the brain even if there is an alteration or damage to the artery that in principle governs it. It also balances the blood supply received by both cerebral hemispheres, allowing the blood that reaches one hemisphere to communicate with the other hemispheres.
As we have said, the circle of Willis is the structure through which the different main arteries that supply the brain are interconnected. Among these arteries, the main ones and from which many others branch are the following (although there are many other branches).
1. Internal carotid artery
carotid arteries They ascend through the body to the head, on both sides of the neck, to end up penetrating the skull (at which point they become called internal carotids). Once inside it, they will be responsible for providing blood to the anterior part of the brain, taking charge of a large part of the supply of oxygen and nutrients to the majority of the brain (both cortex and subcortical structures), to form, together with its branches, the anterior part. of the Willis polygon. Later it will divide into anterior and middle cerebral arteries, among many others.
2. Basilar artery
Another of the main arteries that supply the brain, the basilar artery, appears after the union of the vertebral arteries in the brain stem, which go into the base of the skull directly ascending around the vertebrae. This artery and its branches (the posterior cerebral arteries) are responsible for providing blood flow to the brain stem and the posterior regions of the brain (including the occipital lobe), forming the posterior part of the circle of Willis.
3. Posterior communicating arteries
These are two arteries of great importance, since they allow communication between the internal carotid and the posterior cerebral artery in such a way that the main cerebral arteries on the same side of the brain are connected to each other.
The anterior communicating artery is a small artery that connects the right anterior cerebral artery and the left anterior cerebral artery, acting as a bridge between both hemispheres
5. Anterior cerebral artery
Part of the bifurcation of the internal carotid artery, this artery forms part of the circle or circle of Willis directly. Its branches allow it to irrigate sensorimotor areas and the orbitofrontal, among other areas of interest.
6. Middle cerebral artery
The largest branch of the carotid and the most vulnerable to occlusions, its blood supply tends to be directed towards the interior of the brain. Its blood supply reaches the striatum, the insula, and orbital, frontal, parietal and temporal regions. It follows the Sylvian fissure, which is why it is also called the Sylvian or Silvian artery.
7. Posterior cerebral artery
Artery that arises from the connection between the basilar artery and the posterior communicating artery. Especially important for irrigation of the lower and deeper areas of the temporal and occipital lobes since its action allows aspects related to vision
8. Cerebellar arteries
These are the arteries that help irrigate the cerebellum, as well as other structures of the brain stem. We can find the superior, anteroinferior and posteroinferior cerebellar
9. Spinal arteries
The spinal artery is the artery that supplies blood to the spinal cord, being of great importance for the autonomic nervous system and the transmission of information from the brain to the different organs.
When injuries appear
The Willis polygon is an area of ​​great importance for human beings, with a large number of branches arising in its interconnections that They can hold up to 80% of the cerebral blood supply But sometimes it can happen that this polygon is damaged after a trauma, that an aneurysm appears or that there is a cardiovascular accident in this region.
If any type of obstruction appears in the polygon, it is possible that the irrigated areas will run out of oxygen and die. The consequences can be multiple, from death (if, for example, the nuclei that regulate vital signs are lost) to loss of mental and physical functions, sensitivity or motor ability
Another problem that can occur is the fact that an aneurysm appears (in fact, the circle of Willis is one of the main places where problems of this type usually appear) and ends up producing a stroke, which can have disastrous consequences for the patient. affected subject. And even if the outcome is not fatal, you may lose vision due to compression of the optic chiasm.
