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