Anatomy of Brain Stem Lecture Objectives

Brain Stem Structures

• The structure lateral to the pyramid on the ventral surface of the medulla is the olive.
• The hypoglossal nerve (12th cranial nerve) emerges between the pyramid and the olive from the medulla.

Pons

• The pons is divided into two halves on its ventral surface by the basilar sulcus.
• Pontocerebellar fibers cross the midline and pass through the contralateral middle cerebellar peduncle from the pons to enter the opposite cerebellar hemisphere.

Cranial Nerves

• The trochlear nerve (4th cranial nerve) emerges from the dorsal surface of the brain stem.
• The abducent nerve (6th cranial nerve) emerges from the ventral surface of the brain stem.

Brain Stem Functions

• The reticular formation is responsible for the control of level of consciousness, perception of pain, and regulation of cardiovascular and respiratory systems.
• The vagal triangle overlies the dorsal vagal nucleus.

Midbrain and Hindbrain

• The inferior colliculus forms part of the auditory pathway on the dorsal surface of the midbrain.
• The midbrain is separated from the medulla oblongata by the pons.
• The metencephalon is the part of the hindbrain that subdivides into the pons, cerebellum, and medulla oblongata.
• The brain stem connects the cerebellum to the cerebral cortex and spinal cord through tracts.
• The cranial nerve that emerges from the brain stem and is connected to the cerebellum via cerebellar peduncles is the trigeminal nerve (5th cranial nerve).

Other Structures

• The brain stem is located anterior to the occipital bone.
• The cuneate nucleus marks the site of the dorsal column nuclei.
• The oculomotor nerve (3rd cranial nerve) emerges from the ventral surface of the midbrain.
• The crura cerebri in the midbrain's ventral surface are separated by the interpeduncular fossa.
• The cranial nerves that emerge from the cerebellopontine angle are the trigeminal nerve (5th cranial nerve), the facial nerve (7th cranial nerve), and the vestibulocochlear nerve (8th cranial nerve).

Learn about the components, site, relations, and external features of the brain stem, as well as the cranial nerves emerging from it. This quiz covers key objectives outlined in Professor Ahmed Fathalla Ibrahim's Anatomy lecture at King Saud University.