The basal nuclei

  

The basal nuclei

subcortical, intracerebral masses of gray matter forming 

important parts of the extrapyramidal system. They include:

1) the corpus striatum;

2) the claustrum and; 
                                                                                           

3) the amygdaloid body

1. The corpus striatum, or "striped body" consists of the caudate nucleus, núcleus caudátus and the lenticular nucleus, núcleus lentifórmis

Because the internal capsule runs between the caudate and lenticular nucleus of the basal ganglia, the group of structures looks striped.

The caudate nucleus is a comma-shaped structure which lies medially from the lenticular nucleus. The nucleus has a head, a body and a tail

The head, cáput nuclei caudati forms the lateral wall of the anterior horn of the lateral ventricle. Anteriorly it adjoins the substantia perforata anterior.

The body, corpus nuclei caudati, forms the floor of the central part of the lateral ventricle

The tail, cáuda nuclei caudati forms the roof of the inferior horn of the lateral ventricle and ends by joining the amygdaloid body at the temporal pole.

The lenticular nucleus lies laterally and anteriorly to the thalamus and is separated from it by the capsula interna.

internal capsule is made up of a group of sensory and motor white matter tracts that connect the cerebral cortex with the brain stem and spinal cord.

Fibers of white matter subdivide the lenticular nucleus into a lateral portion called the putamen (putamen=shell) and

a medial portion called the glóbus pállidus (pallid=pale).          Anteriorly and inferiorly the putamen is connected with the head of the caudate nucleus by thin bundles of gray matter, which pass through fibers of the internal capsule.

The caudate nucleus and the putamen have common development and are older than the globus pallidus.

Both these structures have similar neurons content and are united under the term the striatum.

The striatum and the globus pallidus are connected with the brain cortex, the thalamus, nuclei of the brain stem, the cerebellum.

 

The striatum and the globus pallidus unite in one striopallidar sytem.

The striopallidar system provides motor control for fine and large automatic body movements,

particularly the hands and lower limbs;

regulation of muscle tone;

regulstion of several vegetative functions (heat transfer and exchange of carbohydrates in muscular tissue).

 

Damage to the putamen and the globus pallidus results in abnormal body movements, such as slow, purposeless, and involuntary movements of the hands, feet, face, tongue, neck as well as other muscle groups (athetosis).

Axons from the substantia nigra terminate in the caudate and putamen. Damage to these connections causes uncontrollable shaking, called tremor and involuntary movements of skeletal muscles (Parkinsonism).

 

2. The cláustrum is a thin layer of gray matter, placed laterally from the putamen and separated from it by the cápsula extérna.

From the cortex of the insula the calustrum is separated by the cápsula extréma.

The external capsule is a series of white matter fibers from the claustrum to the cerebral cortex.

The extreme capsule is a long association fiber pathway of white matter in the brain that provides bidirectional communication between the claustrum and the insular cortex, and the cortex of the frontal and temporal lobes.

The claustrum is a neopallial structure and obtains numerous connections with the brain cortex.

Both these structures have similar neurons content and are united under the term the striatum.

The striatum and the globus pallidus are connected with the brain cortex, the thalamus, nuclei of the brain stem, the cerebellum.

 

The striatum and the globus pallidus unite in one striopallidar sytem.

The striopallidar system provides motor control for fine and large automatic body movements,

particularly the hands and lower limbs;

regulation of muscle tone;

regulstion of several vegetative functions (heat transfer and exchange of carbohydrates in muscular tissue).

 

Damage to the putamen and the globus pallidus results in abnormal body movements, such as slow, purposeless, and involuntary movements of the hands, feet, face, tongue, neck as well as other muscle groups (athetosis).

Axons from the substantia nigra terminate in the caudate and putamen. Damage to these connections causes uncontrollable shaking, called tremor and involuntary movements of skeletal muscles (Parkinsonism).

 

2. The cláustrum is a thin layer of gray matter, placed laterally from the putamen and separated from it by the cápsula extérna.

From the cortex of the insula the calustrum is separated by the cápsula extréma.

The external capsule is a series of white matter fibers from the claustrum to the cerebral cortex.

The extreme capsule is a long association fiber pathway of white matter in the brain that provides bidirectional communication between the claustrum and the insular cortex, and the cortex of the frontal and temporal lobes.

The claustrum is a neopallial structure and obtains numerous connections with the brain cortex.

Both these structures have similar neurons content and are united under the term the striatum.

The striatum and the globus pallidus are connected with the brain cortex, the thalamus, nuclei of the brain stem, the cerebellum.

 

The striatum and the globus pallidus unite in one striopallidar sytem.

The striopallidar system provides motor control for fine and large automatic body movements,

particularly the hands and lower limbs;

regulation of muscle tone;

regulstion of several vegetative functions (heat transfer and exchange of carbohydrates in muscular tissue).

 

Damage to the putamen and the globus pallidus results in abnormal body movements, such as slow, purposeless, and involuntary movements of the hands, feet, face, tongue, neck as well as other muscle groups (athetosis).

Axons from the substantia nigra terminate in the caudate and putamen. Damage to these connections causes uncontrollable shaking, called tremor and involuntary movements of skeletal muscles (Parkinsonism).

 

2. The cláustrum is a thin layer of gray matter, placed laterally from the putamen and separated from it by the cápsula extérna.

From the cortex of the insula the calustrum is separated by the cápsula extréma.

The external capsule is a series of white matter fibers from the claustrum to the cerebral cortex.

The extreme capsule is a long association fiber pathway of white matter in the brain that provides bidirectional communication between the claustrum and the insular cortex, and the cortex of the frontal and temporal lobes.

The claustrum is a neopallial structure and obtains numerous connections with the brain cortex.

Both these structures have similar neurons content and are united under the term the striatum.

The striatum and the globus pallidus are connected with the brain cortex, the thalamus, nuclei of the brain stem, the cerebellum.

 

The striatum and the globus pallidus unite in one striopallidar sytem.

The striopallidar system provides motor control for fine and large automatic body movements,

particularly the hands and lower limbs;

regulation of muscle tone;

regulstion of several vegetative functions (heat transfer and exchange of carbohydrates in muscular tissue).

 

Damage to the putamen and the globus pallidus results in abnormal body movements, such as slow, purposeless, and involuntary movements of the hands, feet, face, tongue, neck as well as other muscle groups (athetosis).

Axons from the substantia nigra terminate in the caudate and putamen. Damage to these connections causes uncontrollable shaking, called tremor and involuntary movements of skeletal muscles (Parkinsonism).

 

2. The cláustrum is a thin layer of gray matter, placed laterally from the putamen and separated from it by the cápsula extérna.

From the cortex of the insula the calustrum is separated by the cápsula extréma.

The external capsule is a series of white matter fibers from the claustrum to the cerebral cortex.

The extreme capsule is a long association fiber pathway of white matter in the brain that provides bidirectional communication between the claustrum and the insular cortex, and the cortex of the frontal and temporal lobes.

The claustrum is a neopallial structure and obtains numerous connections with the brain cortex.

Both these structures have similar neurons content and are united under the term the striatum.

The striatum and the globus pallidus are connected with the brain cortex, the thalamus, nuclei of the brain stem, the cerebellum.

 

The striatum and the globus pallidus unite in one striopallidar sytem.

The striopallidar system provides motor control for fine and large automatic body movements,

particularly the hands and lower limbs;

regulation of muscle tone;

regulstion of several vegetative functions (heat transfer and exchange of carbohydrates in muscular tissue).

 

Damage to the putamen and the globus pallidus results in abnormal body movements, such as slow, purposeless, and involuntary movements of the hands, feet, face, tongue, neck as well as other muscle groups (athetosis).

Axons from the substantia nigra terminate in the caudate and putamen. Damage to these connections causes uncontrollable shaking, called tremor and involuntary movements of skeletal muscles (Parkinsonism).

 

2. The cláustrum is a thin layer of gray matter, placed laterally from the putamen and separated from it by the cápsula extérna.

From the cortex of the insula the calustrum is separated by the cápsula extréma.

The external capsule is a series of white matter fibers from the claustrum to the cerebral cortex.

The extreme capsule is a long association fiber pathway of white matter in the brain that provides bidirectional communication between the claustrum and the insular cortex, and the cortex of the frontal and temporal lobes.

The claustrum is a neopallial structure and obtains numerous connections with the brain cortex.

 

3. The amygdala, córpus amygdaloideum located in the anterior portion of the temporal lobe, is attached to the tail of the caudate nucleus and acts as the subcortical olfactory center.

It is a part of the limbimc syste.

It is connected with the hypothalamus and participates in the endocrine system regulation and sexual behaviuor formation.

Damage of the amygdaloid body results in aggressive behavior or apathy.

 

The limbic system

During development the superolateral aspects of the diencephalon gradually merge with central areas of the inferomedial surface of the hemispheres. Bordering the whole area of fusion on each side, a series of structures develops in hemisphere’s wall as the limbic system.

Many structures of the limbic system are phylogenetically old and were earlier considered to be predominantly olfactory in function.

The limbic system regulates emotional behavior. 

 

3. The amygdala, córpus amygdaloideum located in the anterior portion of the temporal lobe, is attached to the tail of the caudate nucleus and acts as the subcortical olfactory center.

It is a part of the limbimc syste.

It is connected with the hypothalamus and participates in the endocrine system regulation and sexual behaviuor formation.

Damage of the amygdaloid body results in aggressive behavior or apathy.

 

The limbic system

During development the superolateral aspects of the diencephalon gradually merge with central areas of the inferomedial surface of the hemispheres. Bordering the whole area of fusion on each side, a series of structures develops in hemisphere’s wall as the limbic system.

Many structures of the limbic system are phylogenetically old and were earlier considered to be predominantly olfactory in function.

The limbic system regulates emotional behavior. 

 

3. The amygdala, córpus amygdaloideum located in the anterior portion of the temporal lobe, is attached to the tail of the caudate nucleus and acts as the subcortical olfactory center.

It is a part of the limbimc syste.

It is connected with the hypothalamus and participates in the endocrine system regulation and sexual behaviuor formation.

Damage of the amygdaloid body results in aggressive behavior or apathy.

 

The limbic system

During development the superolateral aspects of the diencephalon gradually merge with central areas of the inferomedial surface of the hemispheres. Bordering the whole area of fusion on each side, a series of structures develops in hemisphere’s wall as the limbic system.

Many structures of the limbic system are phylogenetically old and were earlier considered to be predominantly olfactory in function.

The limbic system regulates emotional behavior. 

 

3. The amygdala, córpus amygdaloideum located in the anterior portion of the temporal lobe, is attached to the tail of the caudate nucleus and acts as the subcortical olfactory center.

It is a part of the limbimc syste.

It is connected with the hypothalamus and participates in the endocrine system regulation and sexual behaviuor formation.

Damage of the amygdaloid body results in aggressive behavior or apathy.

 

The limbic system

During development the superolateral aspects of the diencephalon gradually merge with central areas of the inferomedial surface of the hemispheres. Bordering the whole area of fusion on each side, a series of structures develops in hemisphere’s wall as the limbic system.

Many structures of the limbic system are phylogenetically old and were earlier considered to be predominantly olfactory in function.

The limbic system regulates emotional behavior. 

 

3. The amygdala, córpus amygdaloideum located in the anterior portion of the temporal lobe, is attached to the tail of the caudate nucleus and acts as the subcortical olfactory center.

It is a part of the limbimc syste.

It is connected with the hypothalamus and participates in the endocrine system regulation and sexual behaviuor formation.

Damage of the amygdaloid body results in aggressive behavior or apathy.

 

The limbic system

During development the superolateral aspects of the diencephalon gradually merge with central areas of the inferomedial surface of the hemispheres. Bordering the whole area of fusion on each side, a series of structures develops in hemisphere’s wall as the limbic system.

Many structures of the limbic system are phylogenetically old and were earlier considered to be predominantly olfactory in function.

The limbic system regulates emotional behavior. 

It is involved in the higher integration of visceral, olfactory and somatic information and patterns of short and long-term homeostatic responses.

These include seeking and capturing prey,

courtship,

mating,

rearing youth,

subjective and expressive elements in emotional responses,

the balance between aggressive and communal behavior and the memory formation.

It controls food habits necessary for survival of the species.

 

The structures of the limbic system include:

1) olfactory nerves, bulb, tract, striae and trigone;

2) anterior perforated structure;

3) the cingulated gyrus and the uncus;

4) the hippocampus and the dentate gyrus;

5) the amygdaloid body;

6) the mamillary bodies and the fornix;

7) the anterior nuclei of the thalamus.

 

The hippocampus or cornu Ammonis is a gyrus found on the medial edge of the temporal lobe. It is a portion of the parahippocampal gyrus that extends into the floor of the inferior horn of the lateral ventricle.

It is named for its shape, as hippocampus means "sea horse." The hippocampus is very close to the basal ganglia and to the lateral ventricles

It is very important to memory especially in making new memories.

It is an area where neurons die constantly and are replaced by new neurons.

In Alzheimer's disease, the hippocampus is one of the first regions of the brain to suffer damage; memory problems and disorientation appear among the first symptoms.

People with extensive, bilateral hippocampal damage may experience anterograde amnesia – the inability to form or retain new memories.

The fornix is an archlike anatomical structure or fold, such as the arched band of white matter located beneath the corpus callosum of the brain.

It is made of fibers that begin in the hippocampus on each side of the brain (where they are also known as the fimbria); the separate left and right side are each called the crus of the fornix.

The bundles of fibers come together in the midline of the brain, forming the body of the fornix. The inferior edge of the septum pellucidum is attached to the upper face of the fornix body.

The body of the fornix travels anteriorly and divides again near the anterior commissure into the left and right pillars or columnae fornicis which terminate in the mammilary bodies of the hypothalamus.

Because the limbic system has a primary function in emotions such as pain, pleasure, anger, rage, fear, sorrow, sexual feelings, docility, and affection it is sometimes called emotional brain.

 

Lateral ventricles

Cerebral hemispheres have cavities placed under the corpus callosum – the lateral ventricles, ventriculi laterals.

The cavity of each ventricle corresponds to the form of the hemisphere.

It starts in the frontal lobe with a curved down and laterally anterior horn, cornu anterius, and then it passes through the parietal lobe as a central part, pars centralis.

At the level of the posterior margin of the corpus callosum the central part divides into an inferior horn, cornu inferius, (in the temporal lobe) and a posterior horn, cornu posterius (in the occipital lobe).

The medial wall of the anterior horn is the septum pellucidum, which is a thin layer of cerebral tissue that runs from the anterior part of the corpus callosum down to the fornix.

Septum pellucidum has two layers and a cavity between them.

The lateral wall and the floor of the anterior horn are formed by the head of the caudate nucleus;

the superior wall is the corpus callosum.

Each lateral ventricle communicates with the third ventricle through interventricular foramina (or foramina of Monroe), foramina interventricularia.

The roof of the central part is formed by the undersurface of the corpus callosum;

the floor is formed by corpus nuclei caudate and the superior part of the thalamus.

A layer of fibers of the corpus callosum – the tapetum (a carpetlike layer), surrounds the posterior horn.

The medial wall has an elevation – calcar avis, raised by the calcarine sulcus.

The inferior horn is the largest horn of the lateral ventricles.

The roof and the lateral wall is formed by the tapetum and the tail of the caudate nucleus;

the medial wall has an eminence of white fibers – hippocampus.

The floor has a collateral eminence, eminentia collateralis raised by the collateral sulcus.

The inferior horn and the central part have the choroid plexus, which participates in cerebrospinal fluid production.

 

 

The white matter of hemispheres

The space between the brain cortex and basal nuclei is occupied by the white matter.

It consists of fibers of three types:

association fibers,

projection fibers, and

commissural fibers.

Association fibers connect different cortical areas of the same hemisphere to one another.

These are subdivided into short and long types.

Short association fibers, fibrae arcuatae cerebri, connect adjacent gyri to one another.

Long association fibers connect more widely separated areas of the cortex.

 

There are several fascicules of such fibers.

The cingulum connects the cingulate gyri to different parts of the gyrus fornicatus.

The frontal lobe is connected to the inferior parietal lobule, the occipital lobe and the posterior part of the temporal lobe by the superior longitudinal fasciculus, fasciculus longitudinalis superior.

The temporal and the occipital lobes interconnect by the inferior longitudinal fasciculus, fasciculus longitudinalis inferior.

The orbital surface of the frontal lobe and the temporal pole are connected by the uncinate fasciculus, fasciculus uncinatus.

 

Comissural fibers connect corresponding parts of the two hemispheres as the commissures of the brain.

The biggest is the corpus callosum, which connects the cerebral cortex of the two sides (neopallial commisure).

The middle part of the corpus callosum is the trunk or body, trunkus corporis callosi.

The anterior end is the genu, genu corporis callosi with the rostrum, which is directed downwards and backwards from the genu.

The splenium, splenium corporis callosi is the posterior end forming the thickest part of the corpus callosum.

Two cerebral commissures – the anterior commissure,

1.commissura anterior and the

2.commissure of the fornix, commissura fornicis, are smaller and belong to the rhinencephalon (archipallial commissures).

The anterior commissure connects the olfactory lobes and both parahippocampal gyri; and commissura fornicis connects the hippocampi.

 

 

 

Projection fibers connect the brain cortex with the thalamus and geniculate bodies, and underlying structures of the cerebrum and spinal cord.

Some fibers go to and others go from the cerebral cortex.

Projection fibers in the white matter of the hemisphere close to the brain cortex form the corona radiata, and then they converge to the internal capsule.

The internal capsule, capsula interna, is a large band of fibers between the nucleus lentiformis and the caudate nucleus with the thalamus.

In frontal section, it looks like an oblique white line continuous with the crus cerebri of the midbrain.

 

In horizontal section it appears as a V-shaped structure with concavity directed laterally.         The internal capsule is divided into the anterior limb, crus anterius capsulae internae, between the caudate nucleus and the anterior half of the nucleus lentiformis;

the posterior limb, crus posterius, – between the thalamus and the posterior half of the nucleus lentiformis;

and the genu, genu capsulae internae, bend between the anterior and posterior limbs

The anterior limb contains tracts from the cortex of the frontal lobe to the thalamus and the pons (to the pontine nuclei and the cerebellum).

In the genu and the anterior portion of the posterior limb pass descending pyramidal tracts – tractus corticonuclearis et corticospinalis.

The posterior portion of the posterior limb contains sensory tracts and the descending tracts from the cortex of the occipital and the temporal lobes towards the pons.

Meninges of the brain

The cerebral meninges are continuous with the spinal meninges, have the same basic structure, and bear the same names:

the outer dura mater,

middle arachnoid,

and inner pia mater.

Dúra máter encéphali consists of two layers. The thicker outer periosteal layer tightly adheres to the cranial bones and functions as an inner periosteum of the cranial bones.

The thinner, inner meningeal layer includes a mesothelial layer on its smooth surface.

The two hemispheres of the cerebrum are separated by the extension of the dura mater called the falx cerebri.

In addition, the two hemispheres of the cerebellum are separated by the falx cerebelli.

The cerebrum is separated from the cerebellum by an extension of the dura mater called the tentorium cerebelli.

Near the sella turcica there is a horizontal extension – diaphrágma séllae with a central aperture.

The hypophysis is placed in hypophiseal fossa under the diaphragm sellae.

The dural layers of the brain form the dural venous sinuses, which receive blood from the brain, the meninges and bones of the skull. CFS is poured into some of them.

These sinuses don’t have any muscular layer and valves.

Cranial venous sinuses communicate with veins outside the skull through emissary veins.

These communications help to keep the blood pressure in the sinuses constant.

Venous sinuses:

1. The superior sagittal sinus, sinus sagittális supérior is between the splitting of the superior edge of the falx cerebri and the sulcus sinus sagittalis superior of the frontal, parietal and occipital bones. Posteriorly it terminates in the confluéns sinuum.

2. The inferior sagittal sinus, sinus sagittális inférior passes along the inferior margin of the falx cerebri.

3. The straight sinus, sinus réctus lies in the median plane within the junction of the falx cerebri and the tentorium cerebelli. It is formed anteriorly by the union of the inferior sagittal sinus with v.cerebri magna (vein of Galen) and ends at the internal occipital protuberance by continuing as the transverse sinus.

4. The occipital sinus, sinus occipitális lies between the posterior margin of the falx cerebelli and the crista occipitális intérna. It ends in the confluens sinuum. The superior sagittal, straight and the occipital sinuses form the confluence of sinuses, confluéns sinuum at the eminéntia crucifórmis.

5. The transverse sinus, sinus transvérsus is paired and formed by splitting of the posterior margin of the tentorium cerebelli and lies along the sulcus sinus transverse of the occipital bone. The sinus drains blood from the confluence of sinuses. At the base of the mastoid process it bends downward and becomes the sigmoid sinus.

6. The sigmoid sinus, sinus sigmoideus is the continuation of the transverse sinus. It is paired and S-shaped and extends to the jugular foramen where it becomes the superior bulb of the internal jugular vein.

7. The cavernous sinus, sinus cavernósus is situated in the middle cranial fossa, on either sides of the sphenoid body. The right and left cavernous sinuses communicate with each other through the anterior and posterior intercavernous sinuses, sinus intercavernósus. The cavernous sinuses drain blood to the superior and inferior petrosal sinuses, the pterygoid plexus, and the facial vein through the superior ophalmic vein.

8. The superior and inferior petrosal sinuses, sinus petrósus supérior et inférior lie along the superior and inferior margins of the temporal pyramid in the same-named fissures. The petrosal sinuses drain the cavernos sinuses into the transverse sinus and the inernal jugular vein. Over the clivus of the skull the two inferior petrosal sinuses communicate with each other and form the basilar plexus of veins, pléxus basiláris which communicates with the internal vertebral venous plexus.

Venous sinuses drain blood to the internal jugular veins, vertebral veins and superficial veins of the skull (due to the diploetic veins that pass in diploe of the skull bones and the emissary veins that pass in nutrient foramina of the skull bones).

The arachnoidea encéphali is thin and transparent cover that reflects the way of the internal layer of the dura mater.

Between the two layers is the subdural space, cávum subdurále. Near the venous sinuses the arachnoidea makes finger-like extensions – arachnoid villi, granulatiónes arachnoidáles, which project into the dural venous sinuses and provide secretion of the CSF.

The pia máter encéphali is in contact with nervous tissue and enters the fissures of the brain.

It contains vessels that supply the brain.

In certain places it enters the walls of brain ventricles and participates in the pléxus choroideus formation which produces the CFS.

Between the arachnoidea and the pia mater is the subarachnoid space, cávitas subarachnoidális filled with CSF.

In certain places the subarachnoid space is enlarged and forms the cisterns:

1. The cerebellomedullary cistern, cistérna cerebellomedulláris or cistern magna is between the medulla and the cerebellum. It is used for cisternal puncture. The CFS passes from the 4th ventricle to this cistern through the median and lateral apertures of the 4th ventricle.

2. The interpeduncular cistern, cistérna interpedunculáris is between the crus cerebri and contains the circulus arteriosus cerebri.

3. The cistérna chiasmátis lies in front of the optic chiasma.

4. The cistern of the lateral fossa, cistérna fóssae laterális cérebri lie in the lateral fossa.

 

 

The blood supply of the brain

Branches of the left and right internal carotid and vertebral arteries supply the brain.

Internal carotid artery enters the cavity of the skull and gives anterior and middle cerebral arteries.

Anterior cerebral artery, a. cerebri anterior supplies medial surface of the cortex and frontal lobes.

Middle cerebral artery, a. cerebri media brings blood to the greater part of the superolateral surface, parietal and temporal lobes.

Anterior cerebral arteries are connected by a transverse anastomosis formed by the anterior communicating artery, a. communicans anterior.

Vertebral arteries unite and form one unpaired basillary artery, a. basilaris, which gives branches to supply the cerebellum, the brain stem. A. basillaris terminal branches are two posterior cerebral arteries, a. cerebri posterior which supply occipital lobes. Each posterior cerebral artery is connected with middle cerebral artery by posterior communicating artery, a. communicans posterior, which is the branch of the internal carotid artery.

Cerebral arteries form anastomosis in the form of the circulus arteriosus (circle of Willis). The circle lies in the interpeduncular subarachnoid cistern and equalizes pressure in the arteries of the two sides.

Small branches of cerebral arteries in the pia mater rich the brain and divide into capillaries. There is a blood-brain barrier formed by structures between the blood and nerve cells of the brain. The barrier permits a selective passage of blood contents to nervous tissue. Toxic and harmful substances are ordinary prevented from reaching the brain. Thrombosis of cerebral arteries causes brain infarction.

The blood from capillaries runs into veins. Internal and external cerebral veins terminate in sinuses of the dura mater cerebri: superior and inferior sagittal, transverse, straight, occipital and sigmoid. Sinuses drain the blood to internal jugular veins.

Anterior and posterior spinal arteries, branches of vertebral arteries, supply the spinal cord. Anterior spinal arteries unite right after their origin and form one unpaired trunk. Two vertebral and two posterior spinal arteries form a rhomboid anastomosis (rhombus of Zaharchenko) at the level of the medulla. The blood from the vertebral arteries reaches only up to the cervical segments of the cord. The spinal arteries also receive blood through radicular branches that arise from the vertebral, ascending cervical, deep cervical, intercostals, lumbar and sacral arteries.

Venous blood flows into same named veins and then into internal venous vertebral plexus placed in the epidural space. From this plexus the blood drains into veins, that run along the vertebral column and after into superior and inferior caval veins.

 

 

Circulation of cerebrospinal fluid

The choroid plexus in the brain ventricles produce cerebrospinal fluid (CFS).

CSF circulation occurs in a definite pattern. After the cerebrospinal fluid is produced, it flows through the interventricular foramens (Monro) of the lateral ventricles until it reaches the third ventricle of the brain. It then moves through the cerebral aqueduct and into the fourth ventricle, where it flows to the subarachnoid spaces of the brain and spinal cord through the foramens of Magendie and Luschka.

The CFS circulates throughout the subarachnoid spaces in the brain and spinal cord and then is absorbed into the bloodstream. Arachnois villi and granulations (protrusion of the arachnoid matter through the dura mater into the lumina of venous sinuses) provide liquor absorbtion.

The proper amount of circulating cerebrospinal fluid helps to protect the spinal cord and the brain from injury. CSF provides a protective layer that can absorb the shock from a sudden blow to the head or back.

Hydrocephalus is the excess accumulation of fluid in the subarachnois space and vesicles. Too much CSF can put pressure on the intracranial blood vessels and disrupt the flow of fresh blood to the brain. Low amounts of circulating cerebrospinal fluid removes the protective cushioning around the brain and spinal cord, and can result in brain damage and hemorrhage if these areas are injured.