Transcript PROSENCEPHALON(FOREBRAIN)

DEVELOPMENT OF
PROSENCEPHALON
PROSENCEPHALON
(FOREBRAIN)
 Telencephalon: Rostral part
of forebrain
• Cerebral Hemispheres
 Diencephalon: Caudal &
median part
• optic cup & stalk
• Hypophysis/Pituitary
• Thalmus
• Hypothalmus
• Epiphysis
DIENCEPHALON
• Roof plate
• Alar plates = 2
• Absent floor & basal plates
ROOF PLATE & EPIPHYSIS
• Roof plate
1. Choroid plexus of
3rd ventricle
2. Most caudal part of
roof plate develops
into epiphysis/
pineal body
Pineal body
• Appears as epithelial thickening in the
midline, but by 7th week it begins to
evaginate
• Eventually it becomes a solid organ on
the roof of mesencephalon
• Function: Respond to light and
darkness & affect the endocrine and
behavioral rhythms
• In adults calcium is frequently
deposited in the epiphysis and then
serve as land marks on radiographs of
skull.
ALAR PLATES
• Forms lateral wall of diencephalon
• A groove hypothalamic sulcus divides it
into:
1.Thalamus
2.Hypothalamus
THALAMUS
• Thalamus gradually
projects into the lumen of
diencephalon due to
proliferation of cells
• Frequently the expansion
is so great that two thalami
fuse in mid line forming
massa Intermedia or
Interthalamic connexus
HYPOTHALMUS
• Forms the lower portions
of alar plate
• Differentiate into number
of nuclear masses that
regulate visceral
functions
• Mammillary body forms
a distinct protuberance
on the ventral surface of
hypothalamus on each
side of midline
Hypophysis/Pituitary GlandEctodermal
Develops from two sources:
1. An ectodermal outpocketing of the
stomodeum---- Rathke’s pouch
2. Downward extension of diencephalon---the infundibulum
Cont…
• At 3 weeks Rathke’s pouch appear as
evagination that grows dorsally towards
infundibulum.
• By the end of 2nd month it loses its
connection with the oral cavity
• Comes to lie in close contact with
infundibulum
Cont…
• Cells in the anterior wall rapidly proliferate
and form the ---- anterior lobe/
adenohypophsis.
• A small extension of the lobe is pars
tuberalis that surrounds the infundibulum
• The posterior wall of pouch forms the --pars Intermedia
• Infundibulum give rise to stalk & pars
nervosa----posterior lobe/Neurohypophysis
Hypophysis/Pituitary GlandEctodermal
HYPOPHYSEAL DEFECTS
CRANIOPHARYNGIOMAS
Remnant of Rathke’s pouch
Cerebral Hemispheres
• Arise by 5th week as bilateral evaginations of
lateral wall of forebrain
• Interventricular foramen
CEREBRAL HEMISPHERES
• Middle of 2nd month the basal
part/floor of hemispheres
begins to grow & bulges into
lumen of lateral ventricle &
into floor of foramen of Monro
• In T.S this rapidly growing
region has striated
appearance therefore called
Corpus striatum
• C.H become C-shaped
• Choroid plexus develop in the
region where wall of
hemisphere is attached to roof
of diencephalon
CORPUS STRIATUM
• As the cerebral cortex differentiates the axons passing to &
from the cortex (Internal capsule) break the nuclear masses
into:
dorsomedial portion caudate nucleus
ventrolateral portion the lentiform nucleus
• Medial wall of C.H fuse with lateral wall of diencephalon
CHOROID
FISSURE
• The Lateral ventricle become Cshaped due to growth & curvature
of C.H
• The caudal end of each C.H turns
ventrally & then rostrally, forming
the temporal lobe & in so doing it
carries the ventricle (forming
temporal horn) & Choroid fissure
with it.
CHOROID
PLEXUS
• Choroid plexus protrude in
the lateral ventricle along
the choroid fissure
• The thin medial wall of the
C.H is invaginated along
the choroid fissure by
vascular pia matter to form
choroid plexus of temporal
horn
Growth of cerebral hemispheres
• C.H grow in anterior, posterior
& inferior directions resulting
in formation of frontal,
occipital & temporal lobes.
• As growth in the region of
corpus striatum slows the
region b/w frontal & temporal
lobes depressed & is called
insula
• This region is later overgrown
by other lobes Which
completely covers it at birth.
COMMISSURES
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Anterior commissure- 1st to appear
Hippocamphal commissure
Corpus callosum- 10th week
Habenular commissure
Posterior commissure
Optic chiasma
Congenital anomalies
Cranium Bifidum
Holoprosecrphaly
Schizencephaly
Anencephaly
Hydrocephalus
Arnold Chiari Malformation