The fourth ventricle is located in the posterior cranial fossa between the cerebellum and brainstem. It has five recesses and communicates with the cerebral aqueduct and central canal of the medulla. The roof is formed by the superior cerebellar peduncles and medullary velum, which contains the choroid plexus. The floor is rhomboid-shaped and formed by the pons and medulla, containing important nuclei. The fourth ventricle plays a role in circulation of cerebrospinal fluid and can be affected in conditions like medulloblastoma and hydrocephalus.

1. Fourth ventricle
DR.DEEPAK N KHEDEKAR
DEPT.OF ANATOMY
LTMMC &GH
DEC-2015

2. Introduction…
• Brain develops from the enlarged cranial part
of the neural tube.
• At the end of 4th week, the enlarged cephalic
part shows 3 distinct dilatations- Primary
brain vesicles.
• Cavities of vesicles form the ventricular
system of the adult brain.

3. Ventricular system

4. Primary brain vesicles .
• Craniocaudally, these are:
Prosencephalon (forebrain)
Mesencephalon (mid-brain)
Rhombencephalon (hindbrain).

5. Primary brain vesicles .

6. Ventricular system

7. Cerebrospinal Fluid
• Cerebrospinal fluid (CSF) is similar to that of blood
plasma and interstitial fluid.
• Present in the ventricular system within the CNS and in
the subarachnoid space surrounding the CNS.
• Bathes both the external and internal surfaces of the
brain and spinal cord .
• Provides a protective cushion between the CNS and
the surrounding bones.
• In an adult, the total volume of CSF is about 150 ml,
out of which only 30 ml is in the ventricular system and
remainder in the subarachnoid space.

10. Introduction…
• Tent-like cavity of hindbrain.
• Site- Posterior cranial fossa
• Location-
Cerebellum in front.
Pons and upper part of medulla oblongata
behind.
• Lined with ependyma and filled with CSF

11. Cerebellum-superior view

12. Cerebellum-Inferior view

13. Introduction…

14. Introduction…
Cavity of the ventricle presents-
Triangular outline in sagittal section and
Rhomboidal in shape (lozenge-shaped) in
horizontal section.
• Continuous with…
Cerebral aqueduct of midbrain.
Central canal of medulla oblongata

15. 4th ventricle

16. 4th ventricle
• Recesses
• Angles
• Openings
• Floor
• Roof
• Applied anatomy

17. 1.Recesses…
• 5 in no.
• Extensions from
the cavity.
2- lateral recesses
1- median dorsal
recess
2- lateral dorsal
recesses

18. Lateral Recesses
• One on each side, lies in the interval between…
Inferior cerebellar peduncle ventrally
Peduncle of flocculus dorsally.
• Lateral extremity reaches up to the flocculus
• Opens into the subarachnoid space of
cerebellopontine angle (CP angle) as the lateral
aperture (foramen of Luschka) through which
part of choroid plexus bulges out.

19. 1.Recesses…

20. 1.Recesses…
Median dorsal recess-
• Extends into the white core of the cerebellum
• Lies just above (cranial) to the nodule.
Two lateral dorsal recesses-
• One on each side of median dorsal recess
• Project dorsally above the inferior medullary
velum
• Lies immediately lateral to the nodule.

21. 2.Angles
• 4 angles
Superior - is continuous above with the cerebral
aqueduct of midbrain.
Inferior - is continuous below with the central
canal of the closed part of the medulla oblongata.
2 lateral - one on each side is carried outwards
across the dorsal surface of the inferior cerebellar
peduncle as tubular pouches called lateral recess.

22. 3.Boundaries of the fourth ventricle

23. 4.Roof (posterior wall)
• Tent-shaped,has upper and lower sloping
surfaces.
• Apex of the tent extends posteriorly into the
white core of the cerebellum.
• Upper part of the roof is formed by the
convergence of two Superior cerebellar
peduncles and a thin sheet of white mater
bridging it.

24. Medullary velum
• Bridges the triangular gap between the two
cerebellar peduncles

25. Superior medullary velum
• Bridges the triangular gap between the two
superior cerebellar peduncles
Inferior medullary velum
• formed conjointly by the ventricular ependyma
and the pia mater (of tela choroidea)

26. 4.Roof…
Lower part is formed by…
Inferior medullary velum
a thin sheet of non-nervous tissue, the that
covers it posteriorly.
• intimately related to the nodule of the
inferior vermis of the cerebellum.

27. 4.Roof…
Foramen of Magendie –
• Large aperture in the median plane in lower
part of the inferior medullary velum
• Through which the cavity of fourth ventricle
communicates with the subarachnoid space of
the cerebellomedullary cistern (cisterna
magna).

28. Tela choroidea
• Double layered fold of pia mater
• Lies between the inferior vermis of the cerebellum and
lower part of the roof of the fourth ventricle.
• Layers-
1.Dorsal layer-
• lines the inferior vermis which on reaching the nodule
• is reflected upon itself to form its ventral layer.
• When traced laterally, the dorsal layer is continuous
with the pia mater covering the cerebellar hemisphere.

29. Tela choroidea
2.Ventral layer-
• lies over the roof of
lower part of
fourth ventricle
• continuous with
the pia mater
covering the dorsal
aspect of medulla
oblongata

30. Choroid plexuses
• Formed by capillary plexus of blood vessels
between the two layers of tela choroidea .
• Form the rich vascular fringe that projects
through the lower part of the roof of the fourth
ventricle to form the choroid plexus.
• Derived from the branches of posterior inferior
cerebellar arteries.PICA

31. Choroid plexus
• T’-shaped plx
• projects into the cavity through the lower part of
the roof.
• Vertical limb of ‘T’- is double with foramen of
Magendie intervening between the two limbs.
• Horizontal limb -on either side extends into the
lateral recess, protrudes through the lateral
aperture, foramen of Luschka
• Can be seen on the surface of brain, near the
flocculus.

32. 5.Floor (rhomboid fossa)
Formed by…
Posterior surfaces of the pons
Upper part of the medulla.
• Rhomboid in shape (diamond-shaped)
• Divisible into 3 parts

33. 5.Floor
Divisible into…
1.Upper part: is formed by the posterior surface
of the pons.
2. lower triangular part: is formed by the upper
part of the posterior surface of the medulla.

34. 5.Floor…
3.Intermediate part :
• At the junction of the medulla and pons
• Prolonged laterally on either side over the
inferior cerebellar peduncle as the floor of lateral
recess.
• Bounded above by base of upper triangular part
of the floor and below by a line joining the
horizontal parts of the taenia.
• Surface of intermediate part is marked by the
presence of delicate bundles of transversely
arranged fibres, the striae medullaris.

35. 5.Floor…

36. 5.Floor
• Median sulcus – divides floor into right and left symmetrical
halves.
• Medial eminence- longitudinal elevation on either side of
median sulcus
• Medial eminence is bounded laterally by sulcus limitans.
• Vestibular area- lateral to sulcus limitans, containing vestibular
nuclei.
• Vestibular area lies partly in the pons and partly in the medulla
oblongata.
• Superior fovea – widen triangular depression at the upper end
of sulcus limitans

37. 5.Floor…

38. Locus ceruleus
• Bluish grey area lies above the superior fovea
where the sulcus limitans flattens out
• Colour is imparted by the underlying group of
nerve cells containing melanin pigment which
constitute the substantia ferruginea.
• Neurons of locus ceruleus contain large
quantities of norepinephrine (noradrenaline).

39. Inferior fovea.
• lowermost part of sulcus limitans presents a
small depression
Facial colliculus
• An oval swelling present on either side, the
medial eminence in the pontine part of floor
at the level of superior fovea.
• Swelling is produced by the fibres from the
motor nucleus of facial nerve hooking around
the abducent nucleus (internal genu of facial
nerve).

40. Medullary part of the floor
• From inferior fovea the sulcus limitans
descends obliquely towards the median
sulcus.
• Sulcus divides the medial eminence in the
into two triangles -
Hypoglossal triangle above
 Vagal triangle below.

41. Floor-Hypoglossal triangle
Divided by a faint oblique furrow into…
• Medial part which overlies the nucleus of
hypoglossal nerve
• lateral part overlying the nucleus intercalatus.

42. Floor-Intercalated nucleus
• Described by Rutilio staderini in 1894, Italian
neuroanatomist,also called as Staderini nucleus
• is a group of nerve cells in the medulla oblongata,
between the dorsal nucleus of vagus nerve(lateral
to it ) and the nucleus of hypoglossal
nerve (medial to it).
• Forming part of the Perihypoglossal nuclear
complex.
• Probably involved in the control of the vestibulo-
ocular reflex.
• May contribute to the vertical neural integrator.

43. Floor-Vagal triangle
• Overlies the nuclei of vagus, glossopha-
ryngeal and cranial accessory nerves.
• Crossed by a narrow translucent ridge called
funiculus separans.

44. Area Postrema…
• Small area between
the funiculus
separans above and
the gracile tubercle
below.
• consists of highly
vascular neuroglial
tissue.

45. • Taenia-Infero-lateral margins of the fourth
ventricle are marked by a narrow white ridge
• Two taenia meet at the inferior angle of the
ventricle to form a small fold called obex.
• Obex-roof of the inferior angle of the fourth
ventricle.

46. 6.Openings
• 5 openings -through which cerebrospinal fluid
can leave the cavity of 4th ventricle:
Central aperture in the roof (f.of Magendie)
Two lateral apertures in the roof (f.of Luschka).
Central canal of medulla oblongata.
Cerebral aqueduct of midbrain.

47. 7.Applied anatomy…
• Medullablastoma:
• Most common tumour in this region , mostly in
children.
• Arises from poorly differentiated primitive
neuroectodermal cells of cerebellar vermis and occur.
• highly malignant and produces the signs and
• symptoms of cerebellar lesions, or it may press upon
the vital centres located beneath the floor of the
ventricle causing cardiac irregularities, tachycardia,
irregular respiration, and vasomotor disturbances.

48. Hydrocephalus
• is an abnormal increase in the volume of the
cerebrospinal fluid within the skull.
• If the hydrocephalus is accompanied by a raised
cerebrospinal fluid pressure, then it is due to one of
the following: (1) an abnormal increase in the
formation of the fluid,(2) a blockage of the circulation
of the fluid, or (3) a diminished absorption of the fluid.
• Rarely, hydrocephalus occurs with a normal
cerebrospinal fluid pressure, and in these patients,
there is a compensatory hypoplasia or atrophy of the
brain substance.

49. Thank You