CNS
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a.
b.
c.
The cephalic end shows three
dilatations– the primary brain
vesicles.
Prosencephalon or forebrain.
Mesencephalon or midbrain.
Rhombencephalon or hindbrain.
Two flexures are formed –
a.
Cervical flexure at the junction of
the hindbrain and the spinal cord
b.
Cephalic flexure located in the
midbrain region.
c.
Pontine flexture at middle of
rhombencephalon.
Prosencephalona. Telencephalon or endbrain.
Forms primitive cerebral
hemispheres & Corpus striatum.
b. Diencephalon-optic vesicles,
thalamus, hypothalamus, pars
nervosa of hypophysis cerebri.
Mesencephalon
Mid brain.
Rhombencephalon –
a.Metencephalon
Pons and cerebellum
b. Myelencephalon
Medulla oblongata
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The lumen of the spinal cord is
continuous with that of the brain
vesicles.
The cavity of the rhombencephalon is
known as fourth ventricle.
Cavity of the diencephalon –third
ventricle
Cavity of the cerebral hemisphereslateral ventricles.
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The third and fourth ventricles are
connected to each other through the
lumen of the mesencephalon.
This lumen becomes very narrow and
is then known as the aqueduct of
Sylvius.
The lateral ventricles communicate
with the third ventricle through the
Interventricular Foramina of Monro.
Spina bifida
Embryologic failure of fusion of one or
more vertebral arches; subtypes of
spina bifida are based upon degree and
pattern of deformity associated with
neuroectoderm involvement.
Spina bifida occulta
spina bifida in which there is a spinal
defect, but no protrusion of the cord or
its membrane, although there is often
some abnormality in their development.
Meningocele
Protrusion of the membranes of the
brain or spinal cord through a defect in
the skull or spinal column.
Meningomyelocele
Protrusion of the spinal cord and its
membranes through a defect in the
vertebral column.
Rachischisis
Embryologic failure of fusion of vertebral
arches and neural tube with consequent
exposure of neural tissue at surface;
spina bifida cystica with myelocele or
myeloschisis.
Arnold - Chiari malformation
malformed posterior fossa structures
resulting from caudal traction and
displacement of the rhombencephalon
caused by tethering of the spinal cord;
may or may not be accompanied by
spina bifida and associated anomalies
such as meningomyelocele.
Meningoencephalocele
A protrusion of the meninges and brain
through a congenital defect in the
cranium, usually in the frontal or
occipital region.
Anencephaly
Congenital defective development of
the brain, with absence of the bones
of the cranial vault and absent or
rudimentary cerebral and cerebellar
hemispheres, brainstem, and basal
ganglia.
Hemicephalia or Partial anencephaly
Congenital failure of the cerebrum to
develop normally; usually the
cerebellum and basal ganglia are
represented at least in rudimentary
form.
Hydrocephalus
A condition marked by an excessive
accumulation of fluid resulting in
dilation of the cerebral ventricles and
raised intracranial pressure; may
also result in enlargement of the
cranium and atrophy of the brain.
Congenital hydrocephalus or Primary
hydrocephalus
hydrocephalus due to a developmental
defect of the brain.