This document provides information about the ventricular system of the brain and cerebrospinal fluid (CSF). It details the four ventricles in the brain - two lateral ventricles, the third ventricle, and fourth ventricle. It describes the connections between the ventricles via foramina and discusses the choroid plexus which produces CSF. It then outlines the structures forming the walls and boundaries of each ventricle. Finally, it discusses the composition, circulation and functions of CSF, including cushioning and protecting the brain and spinal cord.

1. DR. ABDUL QADEER
MBBS;(MRCS);FCPS; FICS
Assistant Prof. of Surgery
LCMD, Karachi.
VENTRICULAR SYSTEM OF
BRAIN & CSF

2. Ventricular system
 Four ventricles in the brain, among which:
1. Two lateral ventricles
2. A 3rd ventricle
3. A 4th ventricle
 One terminal ventricle at the end of the central
canal within the spinal cord

4. Foramina connecting the
ventricles
1. Inter-ventricular foramina (of Monro) in each
lateral ventricle connect them with the 3rd
ventricle
2. Cerebral aqueduct (of Sylvius) connects the
3rd ventricle with 4th ventricle
3. Foramen of Magendie connects the 4th
ventricle with central canal of the spinal cord
4. Foramina of Luschka on each side of the 4th
ventricle connects it to the subarachnoid space
around the brain & spinal cord

6. Subarachnoid cisterns
 At some areas around the base of brain, arachnoid
mater does not follow the surface of brain, hence forms
some spaces called sub-arachnoid cisterns, which also
contain CSF. These incluse:
1. Cerebello-medullary cistern (cisterna cerebello-
medullaris)
2. Pontine cistern (cisterna pontis)
3. Inter-peduncular cistern (cisterna inter-
peduncularis)

7. Lateral ventricles
 These are two irregular cavities lying within each
cerebral hemisphere
 It is roughly C-shaped & consist of:
1. A central part or body
2. Three horns: anterior, posterior and inferior, each
extending to frontal, occipital & frontal lobes
respectively
3. Each lateral ventricle communicates with 3rd
ventricle through inter-ventricular foramen of
Monro

8. Ventricles of brain

9. Body (central part) of lateral
ventricle
 Extends from inter-ventricular foramen posteriorly
as far as the posterior end of thalamus
 Here it is continuous with the posterior & inferior
horns
 The body of lateral ventricle has:
1. Roof
2. Floor
3. Medial wall

10. Roof of body of lateral
ventricle
 It is formed by
the under
surface of
corpus
callosum

12. Floor of body of lateral
ventricle
 It is formed by the:
1. Caudate nucleus
2. Lateral margin of the thalamus
3. Choroidal fissure is a slit like gap between the
body of fornix and superior surface of thalamus
through which choroid plexus of the ventricle
projects into the body of the ventricle

14. Medial wall of body of lateral
ventricle
 It is formed by the septum pellucidum anteriorly
 The roof & the floor come together posteriorly to
meet the medial wall

15. Anterior horn of lateral
ventricle
 Lies within frontal lobe of brain
 Continues with body at interventricular foramen
 Anterior horn has:
1. Roof
2. Floor
3. Medial wall

16. Roof of anterior horn of lateral
ventricle
 It is formed by the undersurface of the corpus
callosum
 Anterior horn is limited anteriorly by the genu of
corpus callosum

17. Floor of anterior horn of lateral
ventricle
 Its floor is formed by:
1. Head of caudate nucleus
2. Rostrum of corpus callosum medially having a
small portion

18. Medial wall of anterior horn of
lateral ventricle
 It formed by the:
1. Septum pellucidum
2. Anterior column of the fornix

19. Fornix

20. Posterior horn of lateral
ventricle
 Lies into the occipital lobe of brain
 It has:
1. Roof
2. Lateral wall
3. Medial wall

21. Roof & lateral wall of posterior horn
of lateral ventricle
 Both are formed by the tapetum of the corpus
callosum
 Lateral to the tapetum are the optic radiation

22. Medial wall of posterior horn of
lateral ventricle
 It has two elevations (swellings)
 Superior swelling (also called bulb of the posterior
horn) is formed by the splenial fibers of corpus
callosum which is called forceps major
 Inferior swelling is formed by the calcarine sulcus
and is called calcar avis

23. Inferior horn of lateral ventricle
 It lies in temporal lobe of brain
 It has
1. roof
2. floor

24. Roof of Inferior horn of lateral
ventricle
 It is formed by:
1. Inferior surface of the tapetum of the corpus
callosum and
2. Tail of caudate nucleus

25. Floor of Inferior horn of lateral
ventricle
 It is formed by:
1. Collateral eminence laterally
2. Hippocampus medially

26. Choroid plexus of lateral
ventricle
 It is composed of highly vascular pia mater in two
layers, lined with ependymal cells
 It is situated between fornix superiorly and
thanlamus inferiorly
 It produces CSF

28. Tela choroidea of lateral
ventricles

30. Third ventricle
 It is a slit-like cleft between two thalami
 Communicates anteriorly with lateral ventricles
through interventricular foramina of Monro
 Communicates posteriorly with 4th ventricle through
the cerebral aqueduct of Sylvius
 Its boundaries are:
1. Anterior wall
2. Posterior wall
3. Lateral wall
4. Superior wall or roof
5. Inferior wall or floor

31. Anterior wall of 3rd ventricle
 It is formed by:
1. Lamina terminalis
2. Anterior commisure which connects right & left
temporal lobes

32. Posterior wall of 3rd ventricle
 It is formed by:
1. Cerebral aqueduct below Posterior
commissure above
2. Pineal recess & pineal body above the
commissure
3. Habenular commissure above the pineal
recess

33. Lateral wall of 3rd ventricle
 It is formed by:
1. Thalamus superiorly (both are separated
by
2. Hypothalamus inferiorly hypothalamic
sulcus)
3. Both lateral walls are joined by interthalamic
connections

34. Hypothalamic sulcus

35. Superior wall (Roof) of 3rd
ventricle
 It is formed by:
1. Corpus callosum &
2. Fornix
3. Below them lies choroid plexus of the 3rd
ventricle

36. Inferior wall (floor) of 3rd
ventricle
 It is formed by:
1. Optic chiasma
2. Tuber cinereum
3. Infundibulum
4. Mammillary bodies
5. Hypophysis attached to infundibulum
6. Tegmentum of the cerebral peduncles

41. Cerebral aqueduct of Sylvius
 Connects 3rd ventricle with the 4th and conducts
CSF
 Surrounded by the central gray
 It is devoid of choroid plexus

44. Fourth ventricle
 Tent shaped
 Situated:
1. Anterior to the cerebellum
2. Posterior to the pons
3. Posterior to the upper half of the medulla
oblongata
4. Lined with ependyma
5. Connected above with cerebral aqueduct &
below with central canal of the medulla
oblongata & spinal cord
 It has:
a) Lateral wall (boundaries)
b) Roof

46. Lateral wall (boundaries) of 4th ventricle
 It is formed by:
1. Superior cerebellar peduncle above
2. Inferior cerebellar peduncle below

47. Roof (posterior wall) of 4th
ventricle
 It is tent-shaped & projects into the cerebellum behind
 It communicates with subarachnoid space through 3
foramina
 It is formed by:
1. Two superior cerebellar peduncles above which are
connected by superior medullary vellum
2. Two inferior cerebellar peduncles below which are
connected by inferior medullary vellum
 Inferiorly, the roof is pierced by foramen of
Magendie
 Laterally on each side, it has an opening, the
foramina of Luschka

49. Floor (Rhomboid fossa) of 4th
ventricle
 It is diamond-shaped & formed by:
1. Posterior surface of pons &
2. Cranial (upper) half of medulla oblongata
 The floor is divided into symmetrical halves by median
sulcus
 On each side of this sulcus, there is an elevation, the
medial eminence
 Lateral to the eminence, there is another sulcus, the
sulcus limitans
 Lateral to the sulcus limitans lies vestibular area
 Facial colliculus is a slight swelling at the inferior end
of the medial eminence that is produced by the fibers
from the motor nucleus of the facial nerve looping over
the abducens nucleus

54. Facial colliculus

55. Floor (Rhomboid fossa) of 4th ventricle
 Stria medullaris emerge from the median sulcus and
pass laterally on each side over the medial eminence &
the vestibular area and enter the inferior cerebellar
peduncle to reach the cerebellum
 Below the stria medullaris following structures lie in the
floor of the ventricle
1. Hypoglossal triangle: which indicates the position of
underlying hypoglossal nucleus
2. Vagal triangle: beneath which lies the dorsal motor
nucleus of the vagus
3. Area postrema: is a narrow area between the vagal
triangle & the lateral margin of the ventricle

57. Choroid plexus of 4th ventricle
 It is T-shaped
 Lies in the lower half of the roof of 4th ventricle
 Produces CSF

59. Central canal of medulla oblongata &
spinal cord
 Opens superiorly into the 4th ventricle
 Ends at conus medullaris as terminal ventricle
 Surrounded by the gray matter called the gray
commissure
 It is devoid of choroid plexus

61. Subarachnoid space
 It is the space between arachnoid & pia maters
 Surround brain & spinal cord upto S3 vertebra,
hence includes cauda equina
 Filled with CSF
 In some situations around the brain, the
arachnoid mater does not follow the surface of
brain, hence leaves some spaces called sub-
arachnoid cisterns. These include:
1. Cerebello-medullary cistern
2. Pontine cistern
3. Interpeduncular cistern

62. Pyramid of learning

63. Cerebrospinal fluid (CSF)
 Formed within the ventricles of brain
 Its volume is 150 ml
 It is clear, colorless fluid
 It possesses inorganic salts like blood plasma (e.g.
Na, K, Cl), glucose (equal to the half of blood) and
traces of protein
 Only few lymphocytes (0 to 3 cells/mm3)
 Normal CSF pressure = 60-150 mm of water in
lateral recumbent position
 CSF pressure is raised by straining, coughing, or
compressing the internal jugular veins in the neck

64. PHYSICAL & CHEMICAL COMPOSITION
OF CSF
APPEARANCE Clear & colorless
VOLUME 150 ml
RATE OF PRODUCTION 0.5 ml/minute
PRESSURE (in lat. Recumbent
position)
60-150 ml of water
COMPOSITION
1. Protein 15-45 mg/100 ml
2. Glucose 50-85 mg/100 ml
3. Chloride 720-750 mg/100 ml
NO. OF CELLS 0-3

65. Functions of CSF
1. It bathes the external & internal surfaces of the
brain & spinal cord
2. Serves as cushion between CNS & surrounding
bones, thus protects against mechanical trauma
3. Provides buoyancy
4. Serves as a reservoir to assist in the contents of
the skull e.g. if brain & blood volume increase, CSF
volume decreases
5. Nourishment of nervous tissue
6. Removes the products of neuronal metabolism

66. Functions of CSF
1.
Cushions & protects the CNS from trauma
2.
Provides mechanical buoyancy & support for the
brain
3.
Serves as a reservoir & assists in the regulation of
the contents of the skull
4.
Nourishes the CNS
5.
Removes the metabolites from the CNS
6.
Serves as a pathway for pineal secretions to reach
the pituitary gland

67. Formation of CSF
 CSF is formed in:
1. The choroid plexuses of the lateral, 3rd & 4th
ventricles mainly which secrete it actively
2. Ependymal cells in the above ventricles
3. Brain substance through the perivascular space
4. The production of CSF is NOT pressure
regulated. It continues to be produced even if
the re-absorption mechanisms are obstructed

68. Circulation of CSF
 Lateral ventricles Interventricular
foramina of
Monro Third venticle Cerebral
aqueduct of
Central canal
(foramen of
Magendie)
Sylvius Fourth ventricle
Subarachnoid space
(foramina of

69. Absorption of CSF
 CSF is mainly absorbed by arachnoid villi that
project into the dural venous sinuses, especially
SSS, by piercing dura mater
 Arachnoid villus is a diverticulum of a
subarachnoid space into the venous sinuses
 Arachnoid villi are grouped and form arachnoid
granulations

70. Arachnoid granulations

71. Arachnoid granulations

73. Absorption of CSF
 If venous pressure rises & exceeds the CSF
pressure, compression of the tips of villi closes
the tubules & prevents the reflux of blood into the
subarachnoid space. Thus aracnoid villi serve as
valves
 As the production of CSF is constant, hence the
rate of absorption of it controls the CSF pressure

74. Clinical notes
1. Papilloedema
2. Hydrocephalus
3. Clinical investigations e.g. CT, MRI,
Encephalogram, Ventriculogram
4. CSF & disease

75. Papilloedema
 Optic disc will show bulging in raised intracranial
pressure e.g. by tumor, because optic nerve
carries the meninges around it into the eye

76. Hydrocephalus
 An abnormal increase in the volume of CSF
within the skull
 Intracranial pressure will be raised
 Causes may be:
1. Increased formation of CSF
2. Decreased absorption of CSF
3. Blockage of the circulation of CSF
 Two varieties:
1. Non-communication hydrocephalus
2. Communicating hydrocephalus

77. Non-communicating
hydrocephalus
 The raised CSF pressure will be due to blockage
at some point between its formation at the
choroid plexuses and its exit through the foramina
in the roof of the 4th ventricle

78. Communicating hydrocephalus
 No obstruction in the outflow of CSF

79. Intracranial pneumography
(Encephalogram)
 Air or oxygen is introduced through a spinal tap.
Radiograph of skull is then made

80. Intracranial pneumography
(Ventriculogram)
 Air or oxygen is introduced into the lateral
ventricle through a needle inserted through a hole
in the skull (or through a suture in a young child)
 Then radiograph of the skull is made
 Only ventricles are visualized

81. Encephalogram (ventriculogram)

82. CSF & disease
1. An increase in CSF pressure: may be due to
meningitis, brain edema, brain tumor, cerebral
abscess, hematoma
2. Gross appearance of CSF:
 Cloudy = excessive PMN leukocytes or excessive
protein
3. Increase in WBCs = meningitis, encephalitis
(bacterial/viral)
4. Increased protein = T.B meningitis, poliomyelitis
5. Increased gamma globulin = multiple sclerosis
6. Blood in CSF = puncture of a vertebral vein or
subarachnoid hemorrhage
7. Xanthochromia (yellow color) = presence of
oxyhemoglobin in the fluid some hours after

83. Tumors of the 4th ventricle
(Ependymomas)
 May invade the cerebellum, hence s/s of
cerebellar deficiency
 May compress the nuclear centers situated
beneath the floor of 4th ventricle i.e. hypoglossal,
vagus. Therefore, s/s of movements of tongue,
swallowing, respiration, heart rate, blood pressure
etc.

84. The end