Our brain needs a constant, solid supply of nutrients and oxygen because it is unable to store energy from the food we eat.
This is possible thanks to good blood supply to the central nervous system (CNS), which consists of a complex interconnection of arteries and blood vessels distributed along the spinal cord and brain.
In addition to providing nutrients and oxygen to the brain, the vascularization of the CNS allows it and all of its parts to develop their functions.
Before detailing the functions of the vascularization of the central nervous system, we will briefly discuss the types of arteries that make up the central nervous system.
Arteries of the central nervous system
The vascularization of the central nervous system (CNS) is possible thanks to the arteries that reach the different areas that make up its structure.
To receive this much needed blood supply to the brain, two arterial groups take care of it, coming from the heart and through the aortic artery, thus allowing the body’s metabolic activity to be maintained.
On one side are the vertebral arteries, which are responsible for supplying the complete or posterior area of the brain; joining together so that they form the basilar artery which in turn forms the posterior cerebral artery. These are responsible for supplying blood to the brainstem and cerebellum.
On the other hand, there are the internal carotid arteries, which are responsible for nourishing 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 space or the leptomeningeal space and enter the brain tissue to make sure it receives the nutrients it needs to function properly.
The arteries mentioned above can also be of two types. One type is made up of conductors, which are directed to the lateral surfaces of the brain, and the other type is made up of perforators., which come from conduction arteries 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 at the bottom of the brain where the internal carotid arteries branch out into smaller arteries, being these last ones who they are responsible for supplying oxygen-laden 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, just like the spine: cervical, thoracic, lumbar, sacral, and coccygeal. Each of the segments is responsible for supplying eight pairs of spinal nerves that originate from the spinal canal.
Good blood supply through the venous arteries and the ducts passing through them is essential for the proper functioning of the spinal cord and all of its segments, as will be explained in more detail below.
1. Irrigation of the arteries of the spinal cord
The spinal cord is the area of the central nervous system that is responsible for transmitting messages in and out of the brain to the rest of the body. However, for proper operation, it is crossed by three arterial vessels longitudinally, these being the anterior spinal artery and the two posterior spinal arteries.
This anterior vertebral artery originates in the two vertebral arteries at the level of the oblong spinal cord, also called the medulla oblongata, and descends through the anterior or frontal surface of the spinal cord.
On the other hand, the posterior spinal arteries, which emerge from the vertebral arteries or the posterior inferior cerebellar arteries and leave for the entire or posterior surface of the spinal cord.
The arteries of the spinal cord, mentioned above, need to be strengthened by the radicular arteries, such as the ascending cervical, intercostal and lumbar arteries, in order to be able to supply blood through the spinal cord, on the part where she is. under the cervical segments.
A disorder caused by the irrigation of the spinal cord of the CNS, such as an occlusion of the anterior vertebral artery, leads to what is called “acute thoracic spinal cord syndrome” which leads to paraplegia and incontinence, with loss of sensitivity to temperature and pain. .
2. Drainage of the venous canals of the spinal cord
The drainage action of the venous ducts of the spinal cord occurs by a pattern similar to the arterial irrigation of this area. For that, there are six interconnected venous ducts that are dilated longitudinally through the spinal cord.
These canals constitute the anterior and posterior vertebral veins; both extending to the middle zone. On the other hand, there are the anterolateral veins and the posterolateral veins which are close to the insertion of the anterior and posterior venous roots.
All these blood vessels are responsible for draining, through the anterior and posterior radicular veins, the epidural venous plexus., also known as the internal vertebral venous plexus, which is located between the vertebral peristyle and the dura, which is the outer layer responsible for covering and protecting both the brain and the spinal cord.
In addition, the internal venous plexus communicates with the external vertebral venous plexus, so that it is interconnected with the veins of the ascending lumbar region and with the acidic and hemiacic veins, which perform a special function in providing an alternative route for the blood flow to the right atrium of the heart, if there is a situation where the other chambers are blocked.
Vascularization of the brain
The part of the central nervous system known as the brain is made up of three main areas: the brain, cerebellum, and brainstem. All these areas are at full capacity thanks to good vascularization.
1. Irrigation of the arteries of the brain
The part of the central nervous system known as the brain is supplied by two pairs of blood vessels, better known as internal carotid arteries and vertebral arteries.
Internal carotid artery
The internal carotid artery it is divided between two arteries called the anterior and middle cerebral.
The anterior cerebral artery passes over the optic nerve and then crosses the longitudinal fissure between the two cerebral hemispheres, following the curvature of the corpus callosum, until it irrigates the medial zone of the frontal and parietal lobes. It also joins the blood vessel on the opposite side through the anterior communicating artery. This is why the anterior cerebral artery is responsible for supplying the cerebral areas of the motor and sensory cortex of the lower limb (the legs).
The middle cerebral artery, being the largest of the three arteries in the brain, has a cortical territory of greater extension than the others. Where it originates from, it continues to enter the lateral sulcus of the brain, where it is divided so that its branches are responsible for irritating the lateral area of the temporal, parietal and frontal lobes.
This entire surface covers the primary motor and sensory cortex of the whole body except 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.
The vertebral artery arises from the subclavian artery, going to the transverse holes, located in the cervical vertebrae, until entering the cavity of the skull, passing through the foramen or magnum hole.
On this trip, the vertebral artery branches out through arteries called the anterior and posterior spinal cord, which are responsible for the irrigation of the spinal cord and the oblong spinal cord.
Among all these branches, there is one branch that stands out from the others by having a larger size; it is known as the posterior inferior cerebellar artery, whose function is to irrigate the lower part of the cerebellum.
In pass through the rostral or frontal area, the two vertebral arteries join the medulla oblongata, forming basilar artery.
This basilar artery is branched so that it can irrigate several areas, including the lower and anterior parts of the brain, through the anterior cerebellar artery; also the inner ear, by the labyrinthine artery.
The basilar artery is also subdivided into the superior cerebellar arteries and the posterior cerebral arteries.. The superior cerebellum is responsible for irrigating the upper layer of the cerebellum, while the posterior cerebellum is responsible for irrigating the inferomedial face 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 called the “vertebrobasilar system”. All of this includes a vascular network located at the base of the brain, the aforementioned Willis polygon, also known as 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 which allow it: the venous breasts, the superficial veins and the deep veins.
The deep and superficial cerebral veins are responsible for the drainage of the venous breasts, located in the so-called duramare layer, and are paths that form between the two leaves of the duramare and which in turn are subdivided into:
- Superior sagittal sinus: responsible for receiving blood from the upper cerebral veins.
- If lower sagittal: through which the veins located in the medial face of the hemispheres are drained.
- So straight: in the area from which the deeper structures of the forebrain drain, in addition to the lower sagittal sinus.
The deep cerebral veins, at the same time, they perform the function of drainage of structures located in the internal part of the forebrain. Of note are the choroidal veins and the thalamostriad, which are responsible for the drainage of the thalamus, basal ganglia, hippocampus, choroidal plexus and internal capsule.
It happens they join together to form the internal cerebral vein and, in addition, the two internal cerebral veins form the great cerebral vein or Galien’s, located in the lower part of the corpus callosum, extending through the rectum, located in the cerebellum and responsible for draining the internal jugular vein which receives blood from the face, neck and brain.
The superficial veins are located in the subarachnoid space and its function is to drain the lateral surface of the two cerebral hemispheres, until it reaches the superior sagittal sinus.
Damage to the vascularity of the central nervous system
Stroke occurs when the blood supply to the brain is interrupted, being the equivalent in the brain of a myocardial infarction in the heart. This causes damage which may be irreversible for the sufferer.
As mentioned above, the brain needs to receive nutrients and oxygen through the circuit that makes up the blood supply to the central nervous system; therefore, if this blood supply is interrupted, brain cells begin to fail or even die and can cause what is called a stroke or stroke.
This is most often the case for blockage of one of the blood vessels and, as a result, there is a lack of oxygen, which hinders the proper physical and mental functioning of the person, so that he can suffer serious damage. In addition, with the help of professionals, you can gradually recover the affected functions and even relearn skills.
The best known ways to prevent stroke are to control your blood pressure and cholesterol levels, and to avoid smoking.
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