Vascularization of the Central Nervous System: characteristics and structure.

An overview of the blood vessels responsible for the vascularization of the Central Nervous System.

Our brain needs to receive a constant and solid blood supply full of nutrients and oxygen, since it does not have the capacity to store the energy coming from the food we eat.

This is possible thanks to correct vascularization of the central nervous system (CNS), which is composed of a complexwhich is composed of a complex interconnection of arteries and blood vessels distributed along the spinal cord and the brain.

In addition to supplying nutrients and oxygen to the brain, the vascularization of the CNS allows it and each of its parts to carry out their functions.

Before detailing what the functions of the vascularization of the central nervous system consist of, we will comment, by way of summary, on the types of arteries of which the central nervous system is composed.

Arteries of the central nervous system

The vascularization of the central nervous system (CNS) is possible thanks to the arteries that reach different zones that compose its structure.

To receive this blood supply, so necessary in the brain, there are two groups of arteries that are in charge of it, coming from the heart and through the aorta artery, thus allowing the maintenance of the metabolic activity of the organism.

On the one hand, there are the vertebral arteries.which are responsible for supplying the caudal or posterior area of the brain, joining together to form the basilar artery which, in turn, forms the posterior cerebral artery. These are responsible for supplying blood to the brain stem and cerebellum.

On the other hand, there are the internal carotid arteries, which are responsible for supplying blood to the brain stem and the cerebellum.which have the task of supplying the rostral or frontal area of the brain, forming the anterior and middle cerebral arteries. These arteries are divided into smaller branches that spread through the subarachnoid or leptomeningeal space and enter the encephalic tissue in order to ensure that it is supplied with the necessary nutrients for its proper functioning.

The aforementioned arteries can also be of two types. One type is composed of the conduction arteries, which are directed towards the lateral surfaces of the brain, and the other type is composed of the perforating arteries, which are directed towards the lateral surfaces of the brain.which come from the conduction arteries in order to supply more specific areas.

There is an area where the basilar artery and the carotid arteries connect, a structure called the polygon of Willis, which is the area located in the lower part of the brain and in which the internal carotid arteries are branched into smaller arteries, the latter being responsible for supplying oxygen-carrying blood to 80% of the brain. are in charge of supplying oxygen-charged blood to 80% of the brain..

The vascularization of the spinal cord.

The area of the central nervous system, called the spinal cord, is divided into the following segments, as is the spinal column: cervical, thoracic, lumbar, sacral and coccygeal. Each and every one of these segments is responsible for providing eight pairs of spinal nerves that depart from the spinal canal.

For the correct functioning of the spinal cord and all its segments, a correct vascularization through the arteries and venous conduits that cross it is essential, as will be explained in more detail below.

1. Irrigation of the spinal cord arteries

The spinal cord is the area of the central nervous system responsible for transmitting incoming and outgoing messages from the brain to the rest of the body. However, for proper functioning, is crossed longitudinally by three arterial vessels, the spinal arteryThese are the anterior spinal artery and the two posterior spinal arteries.

This anterior spinal artery originates from the two vertebral arteries located at the level of the medulla oblongata, also known as the medulla oblongata, also known as the medulla oblongata, and descends through the anterior or frontal surface of the medulla.

On the other hand, the posterior spinal arteries, which emerge from the vertebral arteries or in the posterior inferior cerebellar arteries and depart towards the caudal or posterior surface of the medulla.

The aforementioned arteries of the medulla need to be reinforced by the radicular arteries, such as the ascending cervical, intercostal and lumbar arteries, in order to be able to supply blood through the medulla to the part below the cervical segments.

A disorder produced in the irrigation of the spinal cord of the CNS, such as an occlusion in the anterior spinal artery, leads to the so-called "acute thoracic spinal cord syndrome" which entails paraplegia and incontinence, as well as loss of sensitivity to temperature and pain.

2. Drainage of the venous ducts of the spinal cord.

The drainage action of the venous ducts of the spinal cord is produced by a pattern similar to that of the arterial irrigation of this area. To this end, there are six interconnected venous ducts that are longitudinally expanded along the spinal cord..

These ducts constitute the anterior and posterior spinal veins, both extending to the middle zone. On the other hand, there are the anterolateral veins and the posterolateral veins that are close to the insertion of the anterior and posterior venous roots.

These blood vessels together are responsible for draining, through the anterior and posterior radicular veins, to the epidural venous plexus.also known as the internal vertebral venous plexus, which is located between the vertebral peristyle and the dura mater, which is the outer layer that covers and protects both the brain and the spinal cord.

In addition, the internal venous plexus is communicated with the external vertebral venous plexus, so it is interconnected with the ascending lumbar veins and with the azygos and hemi-azygos veins, which fulfill a special function by providing an alternative route for blood circulation to the right atrium of the heart, should a situation arise in which the other cavae are blocked.

The vascularization of the brain

The part of the central nervous system known as the encephalon is composed of three main areas: the cerebrum, the cerebellum and the brainstem. All these areas are at full capacity thanks to proper vascularization.

1. The irrigation of the arteries of the encephalon

The part of the central nervous system known as the encephalon is irrigated by two pairs of blood vessels, better known as the internal carotid arteries and the vertebral arteries.

Internal carotid artery

The internal carotid artery is divided between two arteries known as the anterior and middle cerebral arteries..

The anterior cerebral artery passes over the optic nerve and subsequently crosses the longitudinal fissure between the two cerebral hemispheres, following the curvature of the corpus callosum, to supply the medial aspect of the frontal and parietal lobes. It also joins with the blood vessel on the opposite side through the anterior communicating artery. Therefore, the anterior cerebral artery is responsible for irrigating the cerebral areas of the motor and sensory cortex of the lower limb (legs).

The middle cerebral artery, being the largest of the three arteries of the brain, has a larger cortical territory than the others.The middle cerebral artery, being the largest of the three arteries of the brain, has a cortical territory of greater extension than the others. Starting from the place where it originates, it continues until it penetrates into the lateral sulcus of the brain, where it is divided so that its branches are in charge of irritating the lateral area of the temporal, parietal and frontal lobes.

This entire surface covers the primary motor and sensory cortexes of the whole body, except for the lower limb. In addition, it is responsible for irrigating the auditory cortex and the insula, located deep in the lateral sulcus of the brain.

Vertebral artery

The vertebral artery arises from the subclavian arteryThe vertebral artery arises from the subclavian artery, ascending towards the transverse foramina, located in the cervical vertebrae, until it enters the cavity of the skull, passing through the foramen magnum.

In this journey, the vertebral artery is branched by arteries called the anterior and posterior spinal arterieswhich are in charge of irrigating the spinal cord and the medulla oblongata.

Among all these branches there is a branch that stands out above the rest as it has a larger size; It is known as the posterior inferior cerebellar artery.Its function is to irrigate the inferior part of the cerebellum.

When crossing the rostral or frontal area, the two vertebral arteries join in the area of the medulla oblongata, forming the basilar artery. the basilar artery.

This basilar artery is branched in turn in such a way as to supply multiple areas, including the inferior and anterior parts of the brain, via the anterior cerebellar artery; also the inner ear, via the labyrinthine artery.

The basilar artery is also subdivided between the superior cerebellar arteries and the posterior cerebral arteries.. The superior cerebellar is responsible for supplying the superior layer of the cerebellum, while the posterior cerebral is responsible for supplying the inferomedial aspect of the temporal lobe, as well as the visual cortex of the occipital lobe.

In composition, the irrigation of the brain by the vertebral and basilar arteries has been termed the "vertebrobasilar system". All this comprises a vascular network located at the base of the brain, the aforementioned polygon of Willis, also called the arterial circuit of the brain.

2. Drainage of the venous ducts of the brain

For the drainage of this part of the central nervous system there are three vessels that allow it: the venous sinuses, the superficial veins and the deep veins.

The deep cerebral veins and the superficial veins are responsible for draining the venous sinuses, located in the layer known as the superficial layer of the brain.They are located in the layer known as the dura mater, and are pathways that are formed between the two sheets of the dura mater and are in turn subdivided into:

• Superior sagittal sinus: in charge of receiving blood from the superior cerebral veins.
• Inferior sagittal sinus: through which the veins located on the medial side of the hemispheres are drained.
• Straight sinus: in which area the deepest structures of the forebrain are drained, in addition to the inferior sagittal sinus.

The deep cerebral veins, in turn, drain the structures located in the inner part of the forebrain.. Of particular note are the choroidal and thalamo-striatal veins, which are responsible for draining the thalamus, basal ganglia, hippocampus, choroid plexus and internal capsule.

These veins unite to form the internal cerebral vein and, in addition, the two internal cerebral veins form the cerebral magna or Galen's vein, located in the lower part of the body.located in the inferior part of the corpus callosum, continuing through the straight sinus, located in the cerebellum and in charge of draining the internal jugular vein that receives blood from the face, neck and cerebrum.

The superficial veins are located in the subarachnoid space and their function is to drain the surface of the brain. and their function is to drain the lateral surface of both cerebral hemispheres, until they reach the superior sagittal sinus.

Damage to the vascularization of the central nervous system

Stroke occurs when the vascularization of the brain is interrupted.It is equivalent in the brain to a myocardial infarction in the heart. This causes damage that can be irreversible for the person who suffers from it.

As mentioned above, the brain needs to receive nutrients and oxygen through the circuit that makes up the vascularization of the central nervous system; therefore, if this vascularization is interrupted, the brain cells begin to fail, even dying and causing what is known as stroke or cerebral infarction.

This is produced in most of the times by the obstruction of one of the vessels of the brain. the obstruction of one of the blood vessels. and, for that reason, when there is a lack of oxygen, it hinders the correct physical and mental functioning of the person, so it can suffer serious damage. Also, with the help of professionals can gradually recover the affected functions and even relearn skills.

The best known habits to prevent stroke are the control of Blood Pressure and cholesterol levels, as well as avoiding smoking.