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Ventricular system - Wikipedia

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Ventricular system
The ventricular system is a set of four interconnected cavities
Ventricular system
(ventricles) in the brain, where the cerebrospinal fluid (CSF) is
produced. Within each ventricle is a region of choroid plexus, a
network of ependymal cells involved in the production of CSF.
The ventricular system is continuous with the central canal of the
spinal cord (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.
The ventricular system accounts for the
production and circulation of
cerebrospinal fluid.
Contents
Structure
Ventricles
Development
Function
Flow of cerebrospinal fluid
Protection of the brain
Clinical significance
Additional images
See also
References
Structure
The system comprises four ventricles:
lateral ventricles right and left (one for each hemisphere)
third ventricle
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.
Name
From
To
interventricular
foramina (Monro)
lateral
ventricles
third ventricle
cerebral aqueduct
(Sylvius)
third
ventricle
fourth ventricle
median aperture
(Magendie)
fourth
ventricle
subarachnoid space via the
cisterna magna
right and left lateral
aperture (Luschka)
fourth
ventricle
subarachnoid space via the
cistern of great cerebral vein
Rotating 3D rendering of the four
ventricles and connections. From top to
bottom:
Blue - Lateral ventricles
Cyan - Interventricular foramina (Monro)
Yellow - Third ventricle
Red - Cerebral aqueduct (Sylvius)
Purple - fourth ventricle
Green - continuous with the central
canal
(Aperture to subarachnoid space are
not visible)
Details
Identifiers
Latin
Ventriculi cerebri
MeSH
D002552 (https://meshb.
nlm.nih.gov/record/ui?ui
=D002552)
NeuroNames 2497 (http://braininfo.rpr
c.washington.edu/centra
ldirectory.aspx?ID=2497)
Ventricles
The four cavities of the human brain are called ventricles.[1] The
two largest are the lateral ventricles in the cerebrum, the third
FMA
242787 (https://bioporta
l.bioontology.org/ontolog
ies/FMA/?p=classes&co
nceptid=http%3A%2F%2
Fpurl.org%2Fsig%2Font%
2Ffma%2Ffma242787)
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 of the
hindbrain. The ventricles are concerned with the production and
circulation of cerebrospinal fluid[2]
Anatomical terms of neuroanatomy
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 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 of the spinal cord.
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
Size and location of the ventricular
system in the human head.
layer of cells called ectoderm. 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
3D
embryo.[3]
As the brain develops, by the fourth week of embryological
development three swellings known as brain vesicles 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 prosencephalon,
mesencephalon and rhombencephalon. These in turn divide into five
3D Model of ventricular system
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:[3] 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.[4]
3D rendering of ventricles (lateral
The prosencephalon divides into the telencephalon, which forms the
cortex of the developed brain, and the diencephalon. The ventricles
and anterior views).
contained within the telencephalon become the lateral ventricles, and
the ventricles within the diencephalon become the third ventricle.
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 (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, amygdala, septal nuclei, 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.[5]
Function
Flow of cerebrospinal fluid
The ventricles are filled with
cerebrospinal
fluid
(CSF)
which bathes and cushions
the brain and spinal cord
within their bony confines.
CSF is produced by modified
ependymal
cells
of
the
choroid plexus found in all
components
of
the
The cerebrospinal fluid passes out
through arachnoid villi into the
venous sinuses of the skull.
ventricular system except for
the cerebral aqueduct and
MRI showing flow of CSF
the posterior and anterior
horns
of
the
lateral
ventricles. CSF flows from the
lateral ventricles via the interventricular foramina into the third
ventricle, and then the fourth ventricle via the cerebral aqueduct in
the brainstem. From the fourth ventricle it can pass into the central
canal of the spinal cord or into the subarachnoid cisterns via three
small foramina: the central median aperture and the two lateral
apertures.
The fluid then flows around the superior sagittal sinus to be
A schematic illustration of the
venous sinuses surrounding the
brain.
reabsorbed via the arachnoid granulations (or arachnoid villi) into
the venous sinuses, after which it passes through the jugular vein and
major 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 punctures are performed.
The cerebral aqueduct between the third 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, the three protective membranes of the tough dura
mater, the arachnoid mater and the pia mater. The cerebrospinal fluid (CSF) within the skull and spine
provides further protection and also buoyancy, and is found in the subarachnoid space 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.[6][7]
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. 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 using an endoscope placed within the ventricular system through a burr hole. This allows the
cerebrospinal fluid 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) or of the
ventricles (ventriculitis) caused by infection or the introduction of blood following trauma or haemorrhage
(cerebral haemorrhage or subarachnoid haemorrhage).
During embryogenesis in the choroid plexus of the ventricles, choroid plexus cysts can form.
The scientific study of CT scans of the ventricles in the late 1970s gave new insight into the study of mental
disorders. Researchers found that individuals with schizophrenia had (in terms of group averages) larger
than usual ventricles. This became the first "evidence" that schizophrenia was biological in origin and led to a
renewed interest in its study via the use of imaging techniques. Magnetic resonance imaging (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 and have been explained largely in terms of environmental
factors.[8] 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).[9]
The cave of septum pellucidum has been loosely associated with schizophrenia,[10] post-traumatic stress
disorder,[11] traumatic brain injury,[12] as well as with antisocial personality disorder.[5] CSP is one of the
distinguishing features of individuals displaying symptoms of dementia pugilistica.[13]
Additional images
Transverse
dissection View of ventricles.
Scheme
showing Drawing of a cast of the
showing the ventricles
relations
of
the ventricular
cavities,
of the brain.
ventricles to the surface viewed from above.
of the brain.
View of ventricles and
choroid plexus
See also
Blood–brain barrier
Circumventricular organs
References
1. National Institutes of Health (December 13, 2011). "Ventricles of the brain" (https://www.nlm.nih.gov/medlineplu
s/ency/imagepages/9567.htm). nih.gov.
2. International school of medicine and applied sciences kisumu library
3. Schoenwolf, Gary C. (2009). " "Development of the Brain and Cranial Nerves" ". Larsen's human embryology (4th
ed.). Philadelphia: Churchill Livingstone/Elsevier. ISBN 9780443068119.
4. Rakic, P (October 2009). "Evolution of the neocortex: a perspective from developmental biology" (https://www.ncb
i.nlm.nih.gov/pmc/articles/PMC2913577). Nature Reviews. Neuroscience. 10 (10): 724–35. doi:10.1038/nrn2719
(https://doi.org/10.1038%2Fnrn2719). PMC 2913577 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2913577).
PMID 19763105 (https://www.ncbi.nlm.nih.gov/pubmed/19763105).
5. Raine, Adrian; Lee, Lydia; Yang, Yaling; Colletti, Patrick (2010). "Neurodevelopmental marker for limbic
maldevelopment in antisocial personality disorder and psychopathy". BJPsych" (https://www.ncbi.nlm.nih.gov/pm
c/articles/PMC2930915). The British Journal of Psychiatry. 197 (3): 186–192. doi:10.1192/bjp.bp.110.078485 (ht
tps://doi.org/10.1192%2Fbjp.bp.110.078485). PMC 2930915 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC29
30915). PMID 20807962 (https://www.ncbi.nlm.nih.gov/pubmed/20807962).
6. Klein, S.B., & Thorne, B.M. Biological Psychology. Worth Publishers: New York. 2007.
7. Saladin, Kenneth S. Anatomy & Physiology. The Unit of Form and Function. 5th Edition. McGraw-Hill: New York.
2007
8. Peper, Jiska S.; Brouwer, RM; Boomsma, DI; Kahn, RS; Hulshoff Pol, HE (2007). "Genetic influences on human brain
structure: A review of brain imaging studies in twins". Human Brain Mapping. 28 (6): 464–73.
doi:10.1002/hbm.20398 (https://doi.org/10.1002%2Fhbm.20398). PMID 17415783 (https://www.ncbi.nlm.nih.go
v/pubmed/17415783).
9. Allen JS, Damasio H, Grabowski TJ (August 2002). "Normal neuroanatomical variation in the human brain: an MRIvolumetric study". American Journal of Physical Anthropology. 118 (4): 341–58. doi:10.1002/ajpa.10092 (https://
doi.org/10.1002%2Fajpa.10092). PMID 12124914 (https://www.ncbi.nlm.nih.gov/pubmed/12124914).
10. Galarza M, Merlo A, Ingratta A, Albanese E, Albanese A (2004). "Cavum septum pellucidum and its increased
prevalence in schizophrenia: a neuroembryological classification". The Journal of Neuropsychiatry and Clinical
Neurosciences. 16 (1): 41–6. doi:10.1176/appi.neuropsych.16.1.41 (https://doi.org/10.1176%2Fappi.neuropsych.
16.1.41). PMID 14990758 (https://www.ncbi.nlm.nih.gov/pubmed/14990758).
11. May F, Chen Q, Gilbertson M, Shenton M, Pitman R (2004). "Cavum septum pellucidum in monozygotic twins
discordant for combat exposure: relationship to posttraumatic stress disorder" (https://dash.harvard.edu/bitstrea
m/handle/1/28527471/nihms162099.pdf?sequence=1) (PDF). Biol. Psychiatry. 55 (6): 656–8.
doi:10.1016/j.biopsych.2003.09.018 (https://doi.org/10.1016%2Fj.biopsych.2003.09.018). PMC 2794416 (https://
www.ncbi.nlm.nih.gov/pmc/articles/PMC2794416). PMID 15013837 (https://www.ncbi.nlm.nih.gov/pubmed/150
13837).
12. Zhang L, Ravdin L, Relkin N, Zimmerman R, Jordan B, Lathan W, Uluğ A (2003). "Increased diffusion in the brain of
professional boxers: a preclinical sign of traumatic brain injury?". AJNR. American journal of neuroradiology. 24
(1): 52–7. PMID 12533327 (https://www.ncbi.nlm.nih.gov/pubmed/12533327).
13. McKee, AC; Cantu, RC; Nowinski, CJ; Hedley-Whyte, ET; Gavett, BE; Budson, AE; Santini, VE; Lee, HS; Kubilus, CA;
Stern, RA (Jul 2009). "Chronic traumatic encephalopathy in athletes: progressive tauopathy after repetitive head
injury" (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2945234). Neuropathol Exp Neurol. 68 (7): 709–35.
doi:10.1097/NEN.0b013e3181a9d503 (https://doi.org/10.1097%2FNEN.0b013e3181a9d503). PMC 2945234 (http
s://www.ncbi.nlm.nih.gov/pmc/articles/PMC2945234). PMID 19535999 (https://www.ncbi.nlm.nih.gov/pubmed/1
9535999).
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