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EMBRYOLOGYEMBRYOLOGY
By
Dr. Dalia Saleh
By
Dr. Dalia Saleh
Neural TubeNeural Tube
Dr. Dalia Saleh (Anatomy Dept)
Second Week Second Week
�� EpiblastEpiblast
�� Hypoblast Hypoblast
�� Amniotic cavityAmniotic cavity
�� Yolk sac cavityYolk sac cavity
Dr. Dalia Saleh (Anatomy Dept)
Third Week Third Week
�� Primitive nodePrimitive node
�� Primitive streak Primitive streak
�� Intra embryonic Intra embryonic mesodermmesoderm
�� Notochord Notochord
Dr. Dalia Saleh (Anatomy Dept)
Neural TubeNeural Tube
�� Arises from the ectoderm Arises from the ectoderm
overlying the notochord overlying the notochord
�� Gives rise to the Gives rise to the brainbrain and and
spinal cordspinal cord
Dr. Dalia Saleh (Anatomy Dept)
Neural Tube FormationNeural Tube Formation
�� The notochord induces the The notochord induces the
ectoderm above it which ectoderm above it which
thickens to form the thickens to form the neural neural
plateplate
Dr. Dalia Saleh (Anatomy Dept)
Neural Tube FormationNeural Tube Formation
�� The neural plate folds The neural plate folds to to
formform neural grooveneural groove with with
prominent neural foldsprominent neural folds
�� The The neural foldsneural folds approach approach
each other with deepening each other with deepening
of the neural grooveof the neural groove
Dr. Dalia Saleh (Anatomy Dept)
Neural Tube FormationNeural Tube Formation
�� The neural folds fuse and a The neural folds fuse and a
neural tube neural tube is formedis formed
�� The tube, then, separates The tube, then, separates
from the overlying ectodermfrom the overlying ectoderm
Dr. Dalia Saleh (Anatomy Dept)
Neural Tube ClosureNeural Tube Closure
�� Closure of the neural tube Closure of the neural tube
begins in the future begins in the future neckneck region region
(4(4thth somitesomite).).
�� Then, proceeds Then, proceeds craniallycranially and and
caudallycaudally..
Dr. Dalia Saleh (Anatomy Dept)
Neural Tube ClosureNeural Tube Closure�� The most The most cranialcranial and and caudalcaudal ends ends
of the tubes still open asof the tubes still open as
•• Anterior Anterior neuroporeneuropore
•• PosteriorPosterior neuroporeneuropore
�� The anterior pore will close @ day The anterior pore will close @ day
2525 the posterior @ day the posterior @ day 2727
�� The The lumenlumen of the tube of the tube ��������
ventriclesventricles of the brain and of the brain and centralcentral
canalcanal of spinal cordof spinal cord
Dr. Dalia Saleh (Anatomy Dept)
Development of the BrainDevelopment of the Brain
�� 3 primary vesicles @ 43 primary vesicles @ 4thth week: week:
�� ProsencephalonProsencephalon
�� MesencephalonMesencephalon
�� RhombencephalonRhombencephalon
Dr. Dalia Saleh (Anatomy Dept)
Development of the BrainDevelopment of the Brain
�� 5 secondary vesicles @ 65 secondary vesicles @ 6thth week:week:
�� ProsencephalonProsencephalon ��������
�� TelencephalonTelencephalon
�� DiencephalonDiencephalon
�� MesencephalonMesencephalon
�� RhombencephalonRhombencephalon ��������
�� MetencephalonMetencephalon
�� MylencephalonMylencephalon
Dr. Dalia Saleh (Anatomy Dept)
Development of the Spinal CordDevelopment of the Spinal Cord
�� The cells of the neural tube migrate to form the The cells of the neural tube migrate to form the mantlemantle
layer layer �������� gray matter which differentiates into gray matter which differentiates into
�� An An alaralar plateplate, mostly sensory neurons, mostly sensory neurons
�� A A basal platebasal plate, mostly motor neurons., mostly motor neurons.
�� Separated by Separated by sulcucsulcuc limitanslimitans
Dr. Dalia Saleh (Anatomy Dept)
Development of the Spinal CordDevelopment of the Spinal Cord
�� The cells of the mantle layer have axons which The cells of the mantle layer have axons which
collect in the collect in the marginalmarginal layer layer �������� white matterwhite matter
Dr. Dalia Saleh (Anatomy Dept)
Histogenesis of the Spinal CordHistogenesis of the Spinal Cord
�� First, the neural tube is First, the neural tube is
lined by lined by neuroepithelialneuroepithelial
cellscells
�� They then divide to give:They then divide to give:
�� NeuroblastsNeuroblasts �������� apolarapolar, ,
unipolarunipolar, bipolar, , bipolar, multipolarmultipolar
�� GlioblastsGlioblasts �������� astrocytesastrocytes, ,
oligodendrocytesoligodendrocytes
�� EpendymocytesEpendymocytes
Dr. Dalia Saleh (Anatomy Dept)
Neural Crest CellsNeural Crest Cells
�� Originate from cells of Originate from cells of
neural folds.neural folds.
�� Lie between the neural Lie between the neural
tube and surface tube and surface
ectoderm.ectoderm.
Dr. Dalia Saleh (Anatomy Dept)
Neural Crest CellsNeural Crest Cells
�� They, then, migrate to new locations They, then, migrate to new locations �������� many many
derivativesderivatives
�� GGanglion cells (DRG, Cranial sensory, Autonomic)anglion cells (DRG, Cranial sensory, Autonomic)
�� AArachnoidrachnoid and and piapia matersmaters
�� MMelanocyteselanocytes, , MMesenchymeesenchyme of the pharyngeal archesof the pharyngeal arches
�� EEnteric ganglianteric ganglia
�� SSchwannchwann cells, cells, SSuprarenal medulla cellsuprarenal medulla cells
GG MM SSAA EE
Dr. Dalia Saleh (Anatomy Dept)
Tissues around The Spinal CordTissues around The Spinal Cord
�� Neural crestNeural crest �������� piapia and and
arachnoidarachnoid maters maters
�� MesderomMesderom
�� MicroglialMicroglial cellscells
�� MesenchymaMesenchyma �������� duradura
matermater
�� SomitesSomites �������� become become
vertebrae.vertebrae.
Dr. Dalia Saleh (Anatomy Dept)
Dr. Dalia Saleh (Anatomy Dept)
@ @ 3rd3rd month month �������� samesame length as length as
vertebral canalvertebral canal
@ @ BirthBirth �������� Spinal cord Spinal cord
terminates at terminates at 3rd3rd lumbar lumbar
vertebravertebra
@ @ AdultAdult �������� spinal cord spinal cord
Spinal Cord PositioningSpinal Cord Positioning
terminates at the level of L1