Chapter: Human Neuroanatomy(Fundamental and Clinical): Internal Structure of Brainstem

Development of the Midbrain

The midbrain is developed from the mesencephalon. The cavity of the mesencephalon remains narrow and forms the aqueduct.

DEVELOPMENT OF THE MIDBRAIN

The midbrain is developed from the mesencephalon. The cavity of the mesencephalon remains narrow and forms the aqueduct. As described in the case of the spinal cord, the mantle layer becomes subdivided into a dorsal or alar lamina and a ventral or basal lamina by the appearance of the sulcus limitans. The nuclei which develop from the basal lamina are: (1) the oculomotor nerve nucleus, (2) the trochlear nerve nucleus, and (3) the Edinger Westphal nucleus (GVE)

The alar lamina gives rise to the cells of the colliculi. At first, these form one mass which later becomes subdivided by a transverse fissure. Some cells of the alar lamina migrate ventrally to form the red nucleus and the substantia nigra.

The marginal layer of the ventral part of the mesencephalon is invaded by downward growing fibres of the corticospinal, corticobulbar and corticopontine pathways. This region, thus, becomes greatly expanded, and forms the basis pedunculi (crus cerebri).

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Human Neuroanatomy(Fundamental and Clinical): Internal Structure of Brainstem : Development of the Midbrain |