20 Questions
What structure lies lateral to the pyramid on the ventral surface of the medulla?
Olive
Which nerve emerges between the pyramid and the olive from the medulla?
Hypoglossal (12th) nerve
What divides the pons into two halves on its ventral surface?
Basilar sulcus
Which fibers cross the midline and pass through the contralateral middle cerebellar peduncle from the pons to enter the opposite cerebellar hemisphere?
Transverse pontine (pontocerebellar) fibers
Which cranial nerve emerges from the dorsal surface of the brain stem?
Trochlear (4th)
Which structure is responsible for the control of level of consciousness, perception of pain, and regulation of cardiovascular & respiratory systems?
Reticular formation
What overlies the dorsal vagal nucleus in the vagal triangle?
Vestibular nuclei
Which structure separates the midbrain from the medulla oblongata?
Imaginary line between caudal margins of middle cerebellar peduncle
What forms part of the auditory pathway on the dorsal surface of the midbrain?
Inferior colliculi
Which cranial nerve emerges from the ventral surface of the brain stem?
Trigeminal (5th)
Which part of the brain stem is connected to the cerebellum by the superior, middle, and inferior cerebellar peduncles?
Midbrain
What is the site of the brain stem in relation to the occipital bone?
Basilar part
Which part of the hindbrain subdivides into the pons, cerebellum, and medulla oblongata?
Hindbrain
What is the main function of the brain stem in relation to the tracts between the cerebral cortex and spinal cord?
Pathway of tracts between cerebral cortex & spinal cord
Which structure emerges from the brain stem and is also connected to the cerebellum via cerebellar peduncles?
Facial nerve (CN VII)
Where does the Abducent (6th) nerve emerge from?
Junction between pons and pyramid
Which structure marks the site of the cuneate nucleus?
Cuneate tubercle
From where does the Oculomotor (3rd) nerve emerge?
Medial aspect of crus cerebri
What separates the two crura cerebri in the midbrain's ventral surface?
Interpeduncular fossa
Which cranial nerves emerge from the cerebellopontine angle?
Facial (7th) and Vestibulocochlear (8th)
Study Notes
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.
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