The ventricular system is a set of four interconnected cavities known as cerebral ventricles in the
brain
A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...
.
Within each ventricle is a region of
choroid plexus which produces the circulating
cerebrospinal fluid
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.
CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...
(CSF). The ventricular system is continuous with the
central canal
The central canal (also known as spinal foramen or ependymal canal) is the cerebrospinal fluid-filled space that runs through the spinal cord. The central canal lies below and is connected to the ventricular system of the brain, from which it ...
of the
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...
from the fourth ventricle,
allowing for the flow of CSF to circulate.
All of the ventricular system and the central canal of the spinal cord are lined with
ependyma, a specialised form of
epithelium
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
connected by
tight junctions that make up the
blood–cerebrospinal fluid barrier.
Structure
The system comprises four ventricles:
*
lateral ventricles right and left (one for each hemisphere)
*
third ventricle
The third ventricle is one of the four connected ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and left lateral ...
*
fourth ventricle
There are several
foramina, openings acting as channels, that connect the ventricles. The interventricular foramina (also called the foramina of Monro) connect the lateral ventricles to the third ventricle through which the cerebrospinal fluid can flow.
Ventricles
The four cavities of the human brain are called ventricles. The two largest are the lateral ventricles in the cerebrum, the third ventricle is in the diencephalon of the forebrain between the right and left thalamus, and the fourth ventricle is located at the back of the pons and upper half of the
medulla oblongata
The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (invol ...
of the hindbrain. The ventricles are concerned with the production and circulation of
cerebrospinal fluid
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.
CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...
Development
The structures of the ventricular system are
embryologically derived from the
neural canal, the centre of the
neural tube.
As the part of the primitive neural tube that will develop into the
brainstem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is ...
, 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. The fourth ventricle narrows at the
obex (in the caudal medulla), to become the
central canal
The central canal (also known as spinal foramen or ependymal canal) is the cerebrospinal fluid-filled space that runs through the spinal cord. The central canal lies below and is connected to the ventricular system of the brain, from which it ...
of the
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...
.
In more detail, around the third week of development, the embryo is a three-layered disc. The embryo is covered on the
dorsal surface by a layer of cells called
ectoderm
The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from t ...
. In the middle of the dorsal surface of the embryo is a linear structure called the
notochord. As the ectoderm proliferates, the notochord is dragged into the middle of the developing embryo.
As the
brain develops, by the fourth week of embryological development three swellings known as
brain vesicle
Brain vesicles are the bulge-like features of the early development of the neural tube in vertebrates. Vesicle formation begins shortly after anterior neural tube closure at about embryonic day 9.0 in the mouse and the fourth and fifth gestational ...
s have formed within the embryo around the canal, near where the head will develop. The three primary brain vesicles represent different components of the
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
: the
prosencephalon,
mesencephalon and
rhombencephalon. These in turn divide into five secondary vesicles. As these sections develop around the neural canal, the inner neural canal becomes known as ''primitive'' ventricles. These form the ventricular system of the brain:
The
neural stem cells of the developing brain, principally
radial glial cells, line the developing ventricular system in a transient zone called the
ventricular zone.
* The
prosencephalon divides into the
telencephalon
The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. ...
, which forms the
cortex of the developed brain, and the
diencephalon
The diencephalon (or interbrain) is a division of the forebrain (embryonic ''prosencephalon''). It is situated between the telencephalon and the midbrain (embryonic ''mesencephalon''). The diencephalon has also been known as the 'tweenbrain in o ...
. The ventricles contained within the telencephalon become the
lateral ventricles, and the ventricles within the
diencephalon
The diencephalon (or interbrain) is a division of the forebrain (embryonic ''prosencephalon''). It is situated between the telencephalon and the midbrain (embryonic ''mesencephalon''). The diencephalon has also been known as the 'tweenbrain in o ...
become the
third ventricle
The third ventricle is one of the four connected ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and left lateral ...
.
* The rhombencephalon divides into a
metencephalon and
myelencephalon. The ventricles contained within the rhombencephalon become the
fourth ventricle, and the ventricles contained within the mesencephalon become the
aqueduct of Sylvius.
Separating the anterior horns of the lateral ventricles is the
septum pellucidum: a thin, triangular, vertical membrane which runs as a sheet from the
corpus callosum down to the
fornix. During the third month of fetal development, a space forms between two septal laminae, known as the
cave of septum pellucidum
The cave of septum pellucidum (CSP), cavum septi pellucidi, or cavity of septum pellucidum is a slit-like space in the septum pellucidum that is present in fetuses but usually fuses during infancy. The septum pellucidum is a thin, laminated transl ...
(CSP), which is a marker for fetal neural maldevelopment. During the fifth month of development, the laminae start to close and this closure completes from about three to six months after birth. Fusion of the septal laminae is attributed to rapid development of the
alvei of the
hippocampus
The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic syste ...
,
amygdala
The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex ver ...
,
septal nuclei
The septal area (medial olfactory area), consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum.
The septal nuclei are loc ...
, fornix, corpus callosum and other midline structures. Lack of such limbic development interrupts this posterior-to-anterior fusion, resulting in the continuation of the CSP into adulthood.
Function
Flow of cerebrospinal fluid
The ventricles are filled with
cerebrospinal fluid
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.
CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...
(CSF) which bathes and cushions the brain and
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...
within their bony confines. CSF 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
interventricular foramina into the
third ventricle
The third ventricle is one of the four connected ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and left lateral ...
, and then the
fourth ventricle via the
cerebral aqueduct in the
midbrain
The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal ( alertness), and temperature regulation. The name comes from the Greek ''mesos'', ...
. From the fourth ventricle it can pass into the
central canal
The central canal (also known as spinal foramen or ependymal canal) is the cerebrospinal fluid-filled space that runs through the spinal cord. The central canal lies below and is connected to the ventricular system of the brain, from which it ...
of the
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...
or into the
subarachnoid cisterns
The subarachnoid cisterns are spaces formed by openings in the subarachnoid space, an anatomic space in the meninges of the brain. The space is situated between the two meninges, the arachnoid mater and the pia mater. These cisterns are filled wi ...
via three small foramina: the central
median aperture and the two
lateral apertures.
According to the traditional understanding of cerebrospinal fluid (CSF) physiology, the majority of CSF is produced by the choroid plexus, circulates through the ventricles, the cisterns, and the subarachnoid space to be absorbed into the blood by the arachnoid villi
The fluid then flows around the
superior sagittal sinus to be reabsorbed via the
arachnoid granulation
Arachnoid granulations (also arachnoid villi, and pacchionian granulations or bodies) are small protrusions of the arachnoid mater (the thin second layer covering the brain) into the outer membrane of the dura mater (the thick outer layer). They p ...
s (or arachnoid villi) into the
venous sinuses
The dural venous sinuses (also called dural sinuses, cerebral sinuses, or cranial sinuses) are venous channels found between the endosteal and meningeal layers of dura mater in the brain. They receive blood from the cerebral veins, receive cere ...
, after which it passes through the
jugular vein and major
venous system
Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated ...
. 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
Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid (CSF) for diagnostic testing. The main reason for a lumbar puncture is ...
s are performed.
The
cerebral aqueduct between the
third
Third or 3rd may refer to:
Numbers
* 3rd, the ordinal form of the cardinal number 3
* , a fraction of one third
* 1⁄60 of a ''second'', or 1⁄3600 of a ''minute''
Places
* 3rd Street (disambiguation)
* Third Avenue (disambiguation)
* Hi ...
and
fourth ventricles is very small, as are the foramina, which means that they can be easily blocked.
Protection of the brain
The brain and spinal cord are covered by the
meninges
In anatomy, the meninges (, ''singular:'' meninx ( or ), ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in ...
, the three protective membranes of the tough
dura mater, the
arachnoid mater
The arachnoid mater (or simply arachnoid) is one of the three meninges, the protective membranes that cover the brain and spinal cord. It is so named because of its resemblance to a spider web. The arachnoid mater is a derivative of the neura ...
and the
pia mater. The cerebrospinal fluid (CSF) within the
skull
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...
and spine provides further protection and also
buoyancy
Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the ...
, and is found in the
subarachnoid space
In anatomy, the meninges (, ''singular:'' meninx ( or ), ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in ...
between the pia mater and the arachnoid mater.
The CSF that is produced in the ventricular system is also necessary for chemical stability, and the provision of nutrients needed by the brain. The CSF helps to protect the brain from jolts and knocks to the head and also provides buoyancy and support to the brain against gravity. (Since the brain and CSF are similar in density, the brain floats in neutral buoyancy, suspended in the CSF.) This allows the brain to grow in size and weight without resting on the floor of the cranium, which would destroy nervous tissue.
Clinical significance
The narrowness of the cerebral aqueduct and foramina means that they can become blocked, for example, by blood following a hemorrhagic stroke. As cerebrospinal fluid is continually produced by the choroid plexus within the ventricles, a blockage of outflow leads to increasingly high pressure in the
lateral ventricles. As a consequence, this commonly leads in turn to
hydrocephalus
Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased pressure inside the skull. Older people may have headaches, double vision, poor balance, urinary i ...
. Medically one would call this post-haemorrhagic acquired hydrocephalus, but is often referred to colloquially by the layperson as "water on the brain". This is an extremely serious condition regardless of the cause of blockage. An
endoscopic third ventriculostomy is a surgical procedure for the treatment of hydrocephalus in which an opening is created in the floor of the
third ventricle
The third ventricle is one of the four connected ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and left lateral ...
using an
endoscope placed within the ventricular system through a
burr hole. This allows the
cerebrospinal fluid
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.
CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...
to flow directly to the
basal cisterns, thereby bypassing any obstruction. A surgical procedure to make an entry hole to access any of the ventricles is called a
ventriculostomy. This is done to drain accumulated cerebrospinal fluid either through a temporary catheter or a permanent shunt.
Other diseases of the ventricular system include inflammation of the membranes (
meningitis
Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...
) or of the ventricles (
ventriculitis
Ventriculitis is the inflammation of the ventricles in the brain. The ventricles are responsible for containing and circulating cerebrospinal fluid throughout the brain. Ventriculitis is caused by infection of the ventricles, leading to swelling ...
) caused by
infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...
or the introduction of
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
following trauma or
haemorrhage (
cerebral haemorrhage or
subarachnoid haemorrhage).
During
embryogenesis
An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
in the
choroid plexus of the ventricles,
choroid plexus cysts
Choroid plexus cysts (CPCs) are cysts that occur within choroid plexus of the brain. They are the most common type of intraventricular cyst, occurring in 1% of all pregnancies.
It is believed that many adults have one or more tiny CPCs. The fetal ...
can form.
The
scientific study of
CT scans of the ventricles in the late 1970s gave new insight into the study of
mental disorder
A mental disorder, also referred to as a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may be persistent, relapsing and remitti ...
s. Researchers found that individuals with
schizophrenia
Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social w ...
had (in terms of group averages) larger than usual ventricles. This became the first "evidence" that schizophrenia was
biological
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary in ...
in origin and led to a renewed interest in its study via the use of
imaging techniques.
Magnetic resonance imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...
(MRI) has superseded the use of CT in research in the role of detecting ventricular abnormalities in psychiatric illness.
Whether the enlarged ventricles is a cause or a result of schizophrenia has not yet been established. Enlarged ventricles are also found in organic
dementia
Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...
and have been explained largely in terms of environmental factors.
They have also been found 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).
The
cave of septum pellucidum
The cave of septum pellucidum (CSP), cavum septi pellucidi, or cavity of septum pellucidum is a slit-like space in the septum pellucidum that is present in fetuses but usually fuses during infancy. The septum pellucidum is a thin, laminated transl ...
has been loosely associated with
schizophrenia
Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social w ...
,
post-traumatic stress disorder
Post-traumatic stress disorder (PTSD) is a mental and behavioral disorder that can develop because of exposure to a traumatic event, such as sexual assault, warfare, traffic collisions, child abuse, domestic violence, or other threats o ...
,
traumatic brain injury, as well as with
antisocial personality disorder.
CSP is one of the distinguishing features of individuals displaying symptoms of
dementia pugilistica.
Additional media
File:Gray716.png, Transverse dissection showing the ventricles of the brain.
File:Ventricular system.stl, 3D Model of ventricular system
File:Gray734.png, Scheme showing relations of the ventricles to the surface of the brain.
File:Gray735.png, Drawing of a cast of the ventricular cavities, viewed from above.
File:Gray723.png, View of ventricles and choroid plexus
File:Lateral Ventricles - DK ATLAS.png, Lateral ventricles along with subcortical structures, in glass brain
File:Brain Ventricles Anatomy by Jason Christian.webm, Brain Ventricles Anatomy
See also
*
Blood–brain barrier
The blood–brain barrier (BBB) is a highly selective semipermeable border of endothelial cells that prevents solutes in the circulating blood from ''non-selectively'' crossing into the extracellular fluid of the central nervous system where ne ...
*
Circumventricular organs
References
{{Ventricular system
Brain