Ventricular system
Encyclopedia
The ventricular system is a set of structures containing cerebrospinal fluid
in the brain
. It is continuous with the central canal
of the spinal cord
.
There are several small holes or foramina that connect these ventricles, though only the first two of the list below are generally considered part of the ventricular system:
(CSF) which bathes and cushions the brain and spinal cord
within their bony confines. Cerebrospinal fluid is produced by modified ependymal cells of the choroid plexus
found in all components of the ventricular system except for the cerebral aqueduct
and the posterior
and anterior horns
of the lateral ventricles. CSF flows from the lateral ventricles via the foramina of Monro into the third ventricle
, and then the fourth ventricle
via the cerebral aqueduct
in the brainstem. From there it can pass into the central canal
of the spinal cord
or into the cisterns of the subarachnoid space
via three small foramina: the central foramen of Magendie and the two lateral foramina of Luschka.
The fluid then flows around the superior sagittal sinus
to be reabsorbed via the arachnoid villi into the venous system. CSF within the spinal cord can flow all the way down to the lumbar cistern at the end of the cord around the cauda equina
where lumbar puncture
s are performed.
The aqueduct
between the third
and fourth ventricle
s is very small, as are the foramina, which means that they can be easily blocked, causing high pressure in the lateral ventricles. This is a common cause of hydrocephalus
(known colloquially as "water on the brain"), which is an extremely serious condition due to both the damage caused by the pressure as well as nature of whatever caused the block (e.g. a tumour or inflammatory
swelling). The cavities of the cerebral hemispheres are called lateral ventricles, or 1st & 2nd ventricles. These two ventricles open commonly into the 3rd ventricle by a common opening called foramen of monroe.
, which protect these organs from rubbing against the bones of the skull
and spine
. The cerebrospinal fluid within the skull and spine is found between the pia mater
and the Arachnoid
and provides further cushioning.
The Cerebrospinal Fluid that is produced in the ventricular system has three main purposes: buoyancy
, protection, and chemical stability. The protection purpose comes into play with the meninges: pia mater, and the Arachnoid layer. The CSF is there to protect the brain from striking the cranium when the head is jolted. CSF provided buoyancy and support to the brain against gravity. The buoyancy protects the brain since the brain and CSF are similar in density; this makes the brain float in neutral buoyancy, suspended in the CSF. This allows the brain to attain a decent size and weight without resting on the floor of the cranium, which would kill nervous tissue.
, ventriculitis
) caused by infection
or introduction of blood
following trauma or hemorrhage.
Interestingly, scientific
study of CT scan
s of the ventricles in the late 1970s revolutionized the study of mental disorder. Researchers found that individuals with schizophrenia
had (in terms of group averages) enlarged ventricles compared to healthy subjects. This became the first "evidence" that mental disorder was biological
in origin and led to a reinvigoration of the study of such conditions via modern scientific techniques. Whether the enlargement of the ventricles is a cause or a result of schizophrenia has not yet been ascertained, however. In fact, ventricle volumes have been found to be "mainly explained by environmental factors" and to be extremely diverse between individuals, such that the percentage difference in group averages in schizophrenia studies (+16%) has been described as "not a very profound difference in the context of normal variation" (ranging from 25% to 350% of the mean average). Nowadays, magnetic resonance imaging
(MRI) has superseded the use of CT in research into the role of ventricular abnormalities in psychiatric illness.
The structures of the ventricular system are embryologically
derived from the centre of the neural tube
(the neural canal).
develops, the neural canal expands dorsally and laterally, creating the fourth ventricle
, whereas the neural canal that does not expand and remains the same at the level of the midbrain superior to the fourth ventricle forms the cerebral aqueduct
. Likewise, the neural canal in the spinal cord
that does not change forms the central canal
.
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
in the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
. It is continuous with the central canal
Central canal
For the engineering project, see Indiana Central Canal.The central canal is the cerebrospinal fluid-filled space that runs longitudinally through the length of the entire spinal cord. The central canal is contiguous with the ventricular system of the brain...
of the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
.
Components
The system comprises four ventricles:- right and left lateral ventriclesLateral ventriclesThe lateral ventricles are part of the ventricular system of the brain. Classified as part of the telencephalon, they are the largest of the ventricles....
- third ventricleThird ventricleThe third ventricle is one of four connected fluid-filled cavities comprising the ventricular system within the human brain. It is a median cleft between the two thalami, and is filled with cerebrospinal fluid ....
- fourth ventricleFourth ventricleThe fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...
There are several small holes or foramina that connect these ventricles, though only the first two of the list below are generally considered part of the ventricular system:
| Name | From | To >- | right and left interventricular foramina (Monro) |
lateral ventricles | >- | third ventricle | >- | fourth ventricle | subarachnoid space Subarachnoid space In the central nervous system, the subarachnoid cavity is the interval between the arachnoid membrane and pia mater.... /cisterna magna Cisterna magna The cisterna magna is one of three principal openings in the subarachnoid space between the arachnoid and pia mater layers of the meninges surrounding the brain. The openings are collectively referred to as cisterns. The cisterna magna is located between the cerebellum and the dorsal surface of... >- | right and left Lateral aperture (Luschka) |
fourth ventricle | subarachnoid space/cistern of great cerebral vein Cistern of great cerebral vein The cistern of great cerebral vein is a dilation of the subarachnoid space between the splenium of the corpus callosum and the superior surface of the cerebellum; it extends between the layers of the tela chorioidea of the third ventricle and contains the great cerebral vein.-Synonyms:Synonyms of... |
Flow of cerebrospinal fluid
The ventricles are filled with cerebrospinal fluidCerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
(CSF) which bathes and cushions the brain and spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
within their bony confines. Cerebrospinal fluid is produced by modified ependymal cells of the choroid plexus
Choroid plexus
The choroid plexus is a structure in the ventricles of the brain where cerebrospinal fluid is produced...
found in all components of the ventricular system except for the cerebral aqueduct
Cerebral aqueduct
The mesencephalic duct, also known as the aqueductus mesencephali, aqueduct of Sylvius or the cerebral aqueduct, contains cerebrospinal fluid , is within the mesencephalon and connects the third ventricle in the diencephalon to the fourth ventricle in the mesencephalon, which is between the pons...
and the posterior
Posterior horn of lateral ventricle
The posterior horn of the lateral ventricle passes into the occipital lobe, its direction being backward and lateralward, and then medialward....
and anterior horns
Anterior horn of lateral ventricle
The anterior horn of the lateral ventricle is a portion of the lateral ventricle that passes forward and laterally, with a slight inclination downward, from the interventricular foramen into the frontal lobe, curving around the anterior end of the caudate nucleus...
of the lateral ventricles. CSF flows from the lateral ventricles via the foramina of Monro into the third ventricle
Third ventricle
The third ventricle is one of four connected fluid-filled cavities comprising the ventricular system within the human brain. It is a median cleft between the two thalami, and is filled with cerebrospinal fluid ....
, and then the fourth ventricle
Fourth ventricle
The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...
via the cerebral aqueduct
Cerebral aqueduct
The mesencephalic duct, also known as the aqueductus mesencephali, aqueduct of Sylvius or the cerebral aqueduct, contains cerebrospinal fluid , is within the mesencephalon and connects the third ventricle in the diencephalon to the fourth ventricle in the mesencephalon, which is between the pons...
in the brainstem. From there it can pass into the central canal
Central canal
For the engineering project, see Indiana Central Canal.The central canal is the cerebrospinal fluid-filled space that runs longitudinally through the length of the entire spinal cord. The central canal is contiguous with the ventricular system of the brain...
of the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
or into the cisterns of the subarachnoid space
Subarachnoid space
In the central nervous system, the subarachnoid cavity is the interval between the arachnoid membrane and pia mater....
via three small foramina: the central foramen of Magendie and the two lateral foramina of Luschka.
The fluid then flows around the superior sagittal sinus
Superior sagittal sinus
The superior sagittal sinus , within the human head, is an unpaired area along the attached margin of falx cerebri. It allows blood to drain from the lateral aspects of anterior cerebral hemispheres to the confluence of sinuses...
to be reabsorbed via the arachnoid villi into the venous system. CSF within the spinal cord can flow all the way down to the lumbar cistern at the end of the cord around the cauda equina
Cauda equina
The cauda equina is a structure within the lower end of the spinal column of most vertebrates, that consists of nerve roots and rootlets from above...
where lumbar puncture
Lumbar puncture
A lumbar puncture is a diagnostic and at times therapeutic procedure that is performed in order to collect a sample of cerebrospinal fluid for biochemical, microbiological, and cytological analysis, or very rarely as a treatment to relieve increased intracranial pressure.-Indications:The...
s are performed.
The aqueduct
Aqueduct
An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....
between the third
Third ventricle
The third ventricle is one of four connected fluid-filled cavities comprising the ventricular system within the human brain. It is a median cleft between the two thalami, and is filled with cerebrospinal fluid ....
and fourth ventricle
Fourth ventricle
The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...
s is very small, as are the foramina, which means that they can be easily blocked, causing high pressure in the lateral ventricles. This is a common cause of hydrocephalus
Hydrocephalus
Hydrocephalus , also known as "water in the brain," is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head,...
(known colloquially as "water on the brain"), which is an extremely serious condition due to both the damage caused by the pressure as well as nature of whatever caused the block (e.g. a tumour or inflammatory
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
swelling). The cavities of the cerebral hemispheres are called lateral ventricles, or 1st & 2nd ventricles. These two ventricles open commonly into the 3rd ventricle by a common opening called foramen of monroe.
Protection of the brain
The brain and spinal cord are covered by a series of tough membranes called meningesMeninges
The meninges is the system of membranes which envelopes the central nervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.-Dura...
, which protect these organs from rubbing against the bones of the skull
Human skull
The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...
and spine
Vertebral column
In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...
. The cerebrospinal fluid within the skull and spine is found between the pia mater
Pia mater
Pia mater often referred to as simply the pia, is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord. The word finds its roots in Latin, meaning literally "tender mother." The other two meningeal membranes are the dura mater and the arachnoid mater....
and the Arachnoid
Arachnoid mater
The arachnoid mater, literally from Latin "spider -like mother", is one of the three meninges, the membranes that cover the brain and spinal cord...
and provides further cushioning.
The Cerebrospinal Fluid that is produced in the ventricular system has three main purposes: buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
, protection, and chemical stability. The protection purpose comes into play with the meninges: pia mater, and the Arachnoid layer. The CSF is there to protect the brain from striking the cranium when the head is jolted. CSF provided buoyancy and support to the brain against gravity. The buoyancy protects the brain since the brain and CSF are similar in density; this makes the brain float in neutral buoyancy, suspended in the CSF. This allows the brain to attain a decent size and weight without resting on the floor of the cranium, which would kill nervous tissue.
Role in disease or disorder
Diseases of the ventricular system include abnormal enlargement (hydrocephalus) and inflammation of the CSF spaces (meningitisMeningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
, ventriculitis
Ventriculitis
Ventriculitis is the inflammation of the ventricles in the brain. The ventricles are responsible for containing and circulating cerebrospinal fluid throughout the brain. Ventriculitits is caused by and infection in the ventricles, leading to an immune response in the cells lining them, followed by...
) caused by infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
or introduction of blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
following trauma or hemorrhage.
Interestingly, scientific
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...
study of CT scan
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
s of the ventricles in the late 1970s revolutionized the study of mental disorder. Researchers found that individuals with schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
had (in terms of group averages) enlarged ventricles compared to healthy subjects. This became the first "evidence" that mental disorder was biological
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
in origin and led to a reinvigoration of the study of such conditions via modern scientific techniques. Whether the enlargement of the ventricles is a cause or a result of schizophrenia has not yet been ascertained, however. In fact, ventricle volumes have been found to be "mainly explained by environmental factors" and to be extremely diverse between individuals, such that the percentage difference in group averages in schizophrenia studies (+16%) has been described as "not a very profound difference in the context of normal variation" (ranging from 25% to 350% of the mean average). Nowadays, magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MRI) has superseded the use of CT in research into the role of ventricular abnormalities in psychiatric illness.
Development
The structures of the ventricular system are embryologically
Embryogenesis
Embryogenesis is the process by which the embryo is formed and develops, until it develops into a fetus.Embryogenesis starts with the fertilization of the ovum by sperm. The fertilized ovum is referred to as a zygote...
derived from the centre of the neural tube
Neural tube
In the developing vertebrate, the neural tube is the embryo's precursor to the central nervous system, which comprises the brain and spinal cord...
(the neural canal).
In brainstem
As the part of the primitive neural tube that will become the brain stemBrain stem
In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...
develops, the neural canal expands dorsally and laterally, creating the fourth ventricle
Fourth ventricle
The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...
, whereas the neural canal that does not expand and remains the same at the level of the midbrain superior to the fourth ventricle forms the cerebral aqueduct
Cerebral aqueduct
The mesencephalic duct, also known as the aqueductus mesencephali, aqueduct of Sylvius or the cerebral aqueduct, contains cerebrospinal fluid , is within the mesencephalon and connects the third ventricle in the diencephalon to the fourth ventricle in the mesencephalon, which is between the pons...
. Likewise, the neural canal in the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
that does not change forms the central canal
Central canal
For the engineering project, see Indiana Central Canal.The central canal is the cerebrospinal fluid-filled space that runs longitudinally through the length of the entire spinal cord. The central canal is contiguous with the ventricular system of the brain...
.
External links
- ventricular system and CSF (concise description, University of Washington)
- CSF at answers.com (brief description, excellent diagram of CSF flow)