MID BRAIN

MID BRAIN

Describe the external features:

• Midbrain is the middle part of the brainstem.
• It is connected to the pons below and the diencephalon above.
• It is situated within the posterior cranial fossa.
• External features include the cerebral aqueduct, periaqueductal gray, red nucleus, substantia nigra, and cerebral peduncles.
• The midbrain is continuous with the pons below through the pontomesencephalic sulcus and the diencephalon above through the tentorial notch.

Describe the structures in the transverse section:

• In a transverse section of the midbrain, the following structures are seen:
  • Periaqueductal gray surrounds the cerebral aqueduct.
  • The red nucleus is seen in the tegmentum.
  • The substantia nigra is seen in the tegmentum.
  • The cerebral peduncles are seen on either side of the cerebral aqueduct.
  • The oculomotor nerve (CN III), trochlear nerve (CN IV), and trigeminal nerve (CN V) emerge from the midbrain.
  • The superior cerebellar peduncles are seen below the cerebral peduncles.

Describe the blood supply:

• The midbrain receives blood supply from the superior cerebellar artery, posterior cerebral artery, and the anterior inferior cerebellar artery.
• The superior cerebellar artery supplies the superior cerebellar peduncles and part of the midbrain.
• The posterior cerebral artery supplies the cerebral peduncles, oculomotor nerve (CN III), and the tegmentum.
• The anterior inferior cerebellar artery supplies the red nucleus and the substantia nigra.

Describe the applied anatomy:

• The midbrain is an important structure for the control of various functions such as hearing, vision, and motor functions.
• The midbrain contains the nuclei of the oculomotor nerve (CN III), trochlear nerve (CN IV), and trigeminal nerve (CN V).
• The red nucleus is a part of the rubrospinal tract, which is involved in the control of motor functions.
• The substantia nigra is a part of the nigrostriatal pathway, which is involved in the control of movement.
• The midbrain is also an important structure for the regulation of consciousness, arousal, and sleep.