2. IntroductionâŚ
⢠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. IntroductionâŚ
⢠Tent-like cavity of hindbrain.
⢠Site- Posterior cranial fossa
⢠Location-
ďCerebellum in front.
ďPons and upper part of medulla oblongata
behind.
⢠Lined with ependyma and filled with CSF
14. IntroductionâŚ
Cavity of the ventricle presents-
ďTriangular outline in sagittal section and
ďRhomboidal in shape (lozenge-shaped) in
horizontal section.
⢠Continuous withâŚ
ďCerebral aqueduct of midbrain.
ďCentral canal of medulla oblongata
17. 1.RecessesâŚ
⢠5 in no.
⢠Extensions from
the cavity.
ď2- lateral recesses
ď1- median dorsal
recess
ď2- lateral dorsal
recesses
18. Lateral Recesses
⢠One on each side, lies in the interval betweenâŚ
ďInferior cerebellar peduncle ventrally
ďPeduncle 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.RecessesâŚ
ďMedian dorsal recess-
⢠Extends into the white core of the cerebellum
⢠Lies just above (cranial) to the nodule.
ďTwo 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
ďSuperior - is continuous above with the cerebral
aqueduct of midbrain.
ďInferior - is continuous below with the central
canal of the closed part of the medulla oblongata.
ď2 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.RoofâŚ
Lower part is formed byâŚ
ďInferior medullary velum
ďa 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.RoofâŚ
Foramen of Magendie â
⢠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
⢠Tâ-shaped plx
⢠projects into the cavity through the lower part of
the roof.
⢠Vertical limb of âTâ- 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 byâŚ
ďPosterior surfaces of the pons
ďUpper part of the medulla.
⢠Rhomboid in shape (diamond-shaped)
⢠Divisible into 3 parts
33. 5.Floor
Divisible intoâŚ
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.FloorâŚ
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 â 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 â 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 -
ďHypoglossal triangle above
ď Vagal triangle below.
41. Floor-Hypoglossal triangle
Divided by a faint oblique furrow intoâŚ
⢠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 PostremaâŚ
⢠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:
ďCentral aperture in the roof (f.of Magendie)
ďTwo lateral apertures in the roof (f.of Luschka).
ďCentral canal of medulla oblongata.
ďCerebral aqueduct of midbrain.
47. 7.Applied anatomyâŚ
⢠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.