Internal configuration

Cerebral peduncles

Anterior part, consists of cortical fibres, medially to laterally:

• Corticonuclear fibres
• Corticospinal fibres (destined to the upper limbs, trunk, lower limbs)
• Corticopontine fibres

Tegmentum of midbrain

• Substantia nigra
• Red nucleus
• Medial longitudinal fasciculus
  • Extensively developed through the incorporation of fibres coming from the superior colliculus
  • Passes in front of nuclei of the oculomotor nerve (III)
  • Association tract of the motor nuclei
    → Voluntary motor system
• Dorsal longitudinal fasciculus
  • Within the central grey matter
  • Association tract of the parasympathetic nuclei
    → Autonomic motor system
• • Nuclei of the oculomotor nerve (III)
  • Motor nucleus
  • Accessory preganglionic nuclei, including the Edinger-Westphal nucleus
  • The nerve emerges on the medial surface of the cerebral peduncles
  • Axial sections
  • Posterior view of the brainstem
• Trochlear nerve nucleus (IV)
  • Its axons cross the midline
  • Emergence of the nerve on both sides of the frenulum of the superior medullary velum
  • Axial sections
  • Posterior view of the brainstem
• Medial lemniscus
  moves laterally and posteriorly while ascending within the midbrain
• Lateral lemniscus
• Reticular formation
  • Medial reticular formation: becomes the central grey matter
  • Lateral reticular formation
  • Axial sections
  • Posterior view of the brainstem

Mesencephalic tectum

Or tectal lamina: behind the aqueduct of midbrain

• Nucleus of the superior and inferior colliculi