The components of the brainstem include:

  1. Diencephalon (thalamus, epithalamus, hypothalamus, subthalamus)
  2. Midbrain
  3. Pons
  4. Medulla oblongata

External anatomy of the brainstem

Structures identifiable on the ventral surface of the brainstem include:

  • Optic chiasma, optic tracts.
  • Mamilary bodies, infundibulum.
  • Crus cerebri, oculomotor nerve attachment.
  • Basilar part of pons.
  • Pyramids, olivary eminence.

The transition from the medulla to spinal cord characterized by:

  • Anterior median fissure appears
  • The pyramid disappears
  • Reduction in size
  • Appearance of spinal nerves

What occurs in the spinomedullary junction histologically?


On the dorsal aspect, the following parts of the brainstem are identifiable:

  • Thalamus (with the caudal part, pulvinar overlying part of the midbrain).
  • Epithalamus (pineal, habenular, stria medullaris).
  • Superior colliculi and brachium.
  • Inferior colliculi and brachium.
  • Trochlear nerve emerging caudal to inferior colliculi.
  • Rhomboid fossa overlying pons/medulla.
  • Cuneate and gracile tubercles.