The ventricular system of the brain consists of two lateral ventricles connected to the third and fourth ventricles. Cerebrospinal fluid is produced by the choroid plexus within the ventricles and circulates through the ventricles and subarachnoid space before being reabsorbed into blood vessels. Blockages in cerebrospinal fluid flow can cause hydrocephalus, or excess fluid buildup in the brain. Injuries such as concussions, contusions, and lacerations can damage brain tissue and potentially cause bleeding or swelling.

1. Ventricular System of the
Brain

2. Ventricular System of
the Brain
 The ventricular system of the
brain consists of two lateral
ventricles and the midline 3rd
and 4th ventricles connected
by the cerebral aqueduct.
 Each lateral ventricle opens
through an interventricular
foramen into the 3rd ventricle.
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3. Cerebrospinal fluid (CSF)
 Cerebrospinal fluid (CSF) – filtrate of the blood that helps protect
the brain and may provide nutrients to the structures it bathes.
 CSF is secreted by the choroid plexus within the ventricles, which
are located inside the brain, and it is found in the ventricles, the
subarachnoid space, and the cisterns, which are all continuous
with one another.
 The CSF is returned into the superior sagittal venous sinus by
arachnoid villi, which are essentially a one-way valve for the CSF to
re-enter the bloodstream.
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4. Circulation of cerebrospinal fluid (CSF)
 Cerebrospinal fluid is a clear
colorless fluid, which acts as a
transport medium for nutrients
and waste products and
provides a protective fluid
cushion for the central nervous
system.
 CSF is secreted (at the rate of
400-500 mL daily) by choroidal
epithelial cells (modified
ependymal cells) of the choroid
plexuses in the lateral, 3rd, and 4

5. Circulation of cerebrospinal fluid (CSF)
 The vascular source of the choroid plexus differs between the lateral
and third ventricles, and the fourth ventricle.
 The lateral and third ventricles are supplied anteriorly by the internal
carotid and choroidal branches of the posterior cerebral artery,
whereas the fourth ventricle, being much lower in position, is
supplied by the inferior cerebellar arteries.
 Cerebrospinal fluid is constantly produced at a secretion rate of
0.35-0.40 ml/min, and replaced with an average volume of 150 mL
in the ventricular system/subarachnoid space. Of this volume, about
125 mL is intracranial and 25 mL of this volume lies within the
ventricles
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6. Circulation of cerebrospinal fluid
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CSF drains from lateral ventricle interventricular foramina third ventricle
cerebral
aqueduct of
Slyvius
fourth ventricle median and two lateral apertures
subarachnoid space arachnoid granulations superior sagittal sinus vein
•CSF drains into the subarachnoid space from the 4th ventricle
through a single median aperture and paired lateral
apertures.
•If they are blocked, CSF accumulates and the ventricles
distend, producing compression of the substance of the
cerebral hemispheres.

7.  Luschka
 Lateral
 Drains to
subarachnoid space
 Magendie
 middle
 CSF flow
Lateral ventricle
Foramen of Monroe
3rd ventricle
“Aqueduct of Sylvius”
4th ventricle
Central canal Foramen
of Luschka
& Magendie
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8. Circulation of cerebrospinal fluid
(CSF)
Median aperture Lateral aperture
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9. Cerebrospinal fluid (CSF)
 Clinical Note: If flow of the CSF is blocked, it will lead to
hydrocephalus, which means “water on the brain”.
 If the hydrocephalus is caused by the overproduction or reduced
reabsorption of CSF, it is called a communicating
hydrocephalus.
 A non-communicating hydrocephalus results when the CSF is
blocked somewhere within the ventricular system of the brain and
can not reach the subarachnoid space.
 What type of hydrocephalus would result from meningitis?
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10. Leakage of Cerebrospinal Fluid
 Fractures in the floor of the middle cranial fossa may
result in CSF leakage from the external acoustic meatus
(CSF otorrhea) if the meninges superior to the middle ear
are torn and the tympanic membrane is ruptured.
 Fractures in the floor of the anterior cranial fossa may
involve the cribriform plate of the ethmoid, resulting in
CSF leakage through the nose (CSF rhinorrhea).
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11. Leakage of Cerebrospinal Fluid
 CSF can be distinguished from mucus by testing its
glucose level; the glucose level of the CSF reflects that
of the blood.
 CSF otorrhea and rhinorrhea may be the primary
indications of a cranial base fracture and increase the
risk of meningitis because an infection could spread to
the meninges from the ear or nose
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12. Brain
 Parts of the Brain: The brain is
composed of the
 Cerebrum,
 Cerebellum, and
 Brainstem.
 When the calvaria and dura are
removed, gyri (folds), sulci
(grooves), and fissures (clefts) of
the cerebral cortex are visible
through the delicate arachnoid—pia
layer.
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13. Cerebral Injuries
 Cerebral concussion is an abrupt, brief loss of
consciousness immediately after a head injury.
Consciousness may be lost for only 8-10 sec, as occurs in
a knockdown during boxing.
 The injuries result from acceleration and deceleration of
the head that shears or stretches axons (diffuse axonal
injury). The sudden stopping of the moving head results
in the brain hitting the suddenly stationary cranium.
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14. Cerebral Injuries
 Cerebral contusion results from brain trauma in which the pia is
stripped from the injured surface of the brain and may be torn,
allowing blood to enter the subarachnoid space. It may result in an
extended loss of consciousness, but if there is no diffuse axonal
injury, brain swelling, or secondary hemorrhage, recovery from a
contusion may be excellent.
 Cerebral lacerations are often associated with depressed cranial
fractures or gunshot wounds. Lacerations result in rupture of blood
vessels and bleeding into the brain and subarachnoid space,
causing increased intracranial pressure and cerebral compression.
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15. Cerebral compression
 Cerebral compression may be produced by:
 Intracranial collections of blood.
 Obstruction of CSF circulation or absorption.
 Intracranial tumours or abscesses.
 Brain swelling caused by brain edema, an increase in
brain volume resulting from an increase in water and
sodium content
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