Development of the brain Lecture Content The 1stry divisions of the developing brain Development of the medulla obl...
Lecture Content
The 1stry divisions of the developing brain
Development of the medulla oblongata
There are basal & alar plates in the hind brain, separated by the sulcus limitans
As the 4th ventricle enlarges, the alar plate comes lateral to the basal plate
Basal plate forms the motor nuclei of IX, X, XI & XII cranial nerves (They are situated medial to the sulcus limitans)
Alar plate forms the sensory nuclei of the V, VIII, IX & X cranial nerves, gracile & cuneate nuclei and Olivary nuclei
As the roof plate becomes stretched into a thin layer, tela choroidea projects into the cavity of the 4th ventricle to form the choroid plexus
During the 4th & 5th months, foramina of Luschka & foramen of Magendie are formed
Descending motor fibers from the cortex produce a prominent swelling in the anterior aspect of MO called the pyramids
Development of the pons
Transverse section through the caudal part of the metencephalon. Note the differentiation of the various motor and sensory nuclear areas in the basal and alar plates, respectively
It’s formed from the anterior part of the Metencephalon
It has also cellular contributions from the alar part of the Myelencephalon
Basal plate forms the motor nuclei of V, VI & VII cranial nerves
Alar plate forms
Sensory nucleus of V & VII
Vestibular cochlear nuclei of VIII
Pontine nuclei
Axons of the pontine nuclei go to the developing cerebellum of the opposite side (Rhombic lip) & form
Transverse pontine fibers
Middle cerebellar peduncle
Development of the cerebellum
Dorsal view of the mesencephalon and rhombencephalon in an 8-week embryo
Similar view in a 4-month embryo
It’s formed from the posterior part of the alar plate of the Metencephalon
On each side, alar plates bend medially to form the rhombic lip
As the lips enlarges, they project over the roof plate of the 4th ventricle & unite with each other to form the cerebellum
At 12th week, vermis & 2 cerebellar hemispheres can be recognized
Matrix cells situated close to the ventricle form neuroblasts & migrate to the cerebellum to form the cerebellar cortex
Neuroblasts that remained close to the ventricles differentiate into dentate & other cerebellar nuclei
Development of the midbrain
Mid brain develops from the midbrain vesicle
Cavity becomes much small to form the cerebral aqueduct
Basal plate forms
Motor nuclei of the 3rd & 4th cranial nerves
Red nuclei
Substantia nigra
Reticular formation
The marginal zone of basal plates on each side enlarges to form basis pedunculi (The descending motor tracts are situated in that region – Cortico pontine, corticobulbar & corticospinal tracts)
The 2 alar plates & the roof plate forms the Tectum
The alar plate forms the sensory neurons of the superior & inferior colliculi
Development of the medulla oblongata
There are basal & alar plates in the hind brain, separated by the sulcus limitans
As the 4th ventricle enlarges, the alar plate comes lateral to the basal plate
Basal plate forms the motor nuclei of IX, X, XI & XII cranial nerves (They are situated medial to the sulcus limitans)
Alar plate forms the sensory nuclei of the V, VIII, IX & X cranial nerves, gracile & cuneate nuclei and Olivary nuclei
As the roof plate becomes stretched into a thin layer, tela choroidea projects into the cavity of the 4th ventricle to form the choroid plexus
During the 4th & 5th months, foramina of Luschka & foramen of Magendie are formed
Descending motor fibers from the cortex produce a prominent swelling in the anterior aspect of MO called the pyramids
Development of the pons
Transverse section through the caudal part of the metencephalon. Note the differentiation of the various motor and sensory nuclear areas in the basal and alar plates, respectively
It’s formed from the anterior part of the Metencephalon
It has also cellular contributions from the alar part of the Myelencephalon
Basal plate forms the motor nuclei of V, VI & VII cranial nerves
Alar plate forms
Sensory nucleus of V & VII
Vestibular cochlear nuclei of VIII
Pontine nuclei
Axons of the pontine nuclei go to the developing cerebellum of the opposite side (Rhombic lip) & form
Transverse pontine fibers
Middle cerebellar peduncle
Development of the cerebellum
Dorsal view of the mesencephalon and rhombencephalon in an 8-week embryo
Similar view in a 4-month embryo
It’s formed from the posterior part of the alar plate of the Metencephalon
On each side, alar plates bend medially to form the rhombic lip
As the lips enlarges, they project over the roof plate of the 4th ventricle & unite with each other to form the cerebellum
At 12th week, vermis & 2 cerebellar hemispheres can be recognized
Matrix cells situated close to the ventricle form neuroblasts & migrate to the cerebellum to form the cerebellar cortex
Neuroblasts that remained close to the ventricles differentiate into dentate & other cerebellar nuclei
Development of the midbrain
Mid brain develops from the midbrain vesicle
Cavity becomes much small to form the cerebral aqueduct
Basal plate forms
Motor nuclei of the 3rd & 4th cranial nerves
Red nuclei
Substantia nigra
Reticular formation
The marginal zone of basal plates on each side enlarges to form basis pedunculi (The descending motor tracts are situated in that region – Cortico pontine, corticobulbar & corticospinal tracts)
The 2 alar plates & the roof plate forms the Tectum
The alar plate forms the sensory neurons of the superior & inferior colliculi
