DEVELOPMENT OF PROSENCEPHALON
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Transcript of DEVELOPMENT OF PROSENCEPHALON
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DEVELOPMENT OF PROSENCEPHALON
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PROSENCEPHALON(FOREBRAIN)
Telencephalon: Rostral part of forebrain
• Cerebral Hemispheres Diencephalon: Caudal &
median part • optic cup & stalk • Hypophysis/Pituitary• Thalmus• Hypothalmus• Epiphysis
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DIENCEPHALON
• Roof plate• Alar plates = 2• Absent floor & basal plates
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ROOF PLATE & EPIPHYSIS• Roof plate
1. Choroid plexus of 3rd ventricle
2. Most caudal part of roof plate develops into epiphysis/ pineal body
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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.
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ALAR PLATES
• Forms lateral wall of diencephalon• A groove hypothalamic sulcus divides it
into:
1.Thalamus
2.Hypothalamus
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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
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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
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Hypophysis/Pituitary Gland-Ectodermal
Develops from two sources:
1. An ectodermal outpocketing of the stomodeum---- Rathke’s pouch
2. Downward extension of diencephalon---- the infundibulum
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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
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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
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Hypophysis/Pituitary Gland-Ectodermal
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HYPOPHYSEAL DEFECTSCRANIOPHARYNGIOMAS
Remnant of Rathke’s pouch
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Cerebral Hemispheres• Arise by 5th week as bilateral evaginations of
lateral wall of forebrain • Interventricular foramen
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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
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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
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CHOROID FISSURE
• The Lateral ventricle become C-shaped 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.
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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
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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.
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COMMISSURES
• Anterior commissure- 1st to appear• Hippocamphal commissure• Corpus callosum- 10th week• Habenular commissure• Posterior commissure• Optic chiasma
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Congenital anomalies
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Cranium Bifidum
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Holoprosecrphaly
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Schizencephaly
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Anencephaly
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Hydrocephalus
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Arnold Chiari Malformation
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