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.
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.
8.
9.
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
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
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.
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.
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.
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.
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
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.