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Development of the brain

 Development of the brain

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 brain Development of the brain Reviewed by Ucfm on January 28, 2012 Rating: 5
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