Brainstem

Question 1

External features of medulla

Answer 1

Ventral aspect
Elevations: on each side of the median sulcus
1. Pyramid
2. Olive
3. Inferior cerebellar peduncle- connecting medulla with cerebellum

Fissures:
1. Anterior median sulcus- obliterated in the lower part by pyramidal decussation
2. Pre-Olivery fissure
3. Post-olivery fissure

Cranial nerves
1. Glossopharyngeal
2. Vagus
3. Accesory
4. Hypoglossal

Dorsal aspect

Question 2

External features of pons

Answer 2

Ventral:
Basilar groove- formed by basilar artery
Middle cerebellar peduncle
Trigeminal nerve origin
Pontomedullary junction/ sulcus

Dorsal:
-floor of 4th ventricle
Median sulcus
Medial eminence - has facial colliculus
Sulcus limitans- junction between motor and sensory columns
Vestibular area
Stria medullaris- junction between pons and medulla

Transverse pontine fibers collect to form middle cerebellar peduncle
Middle four cranial nerves exit from the pons:
1. Trigeminal nerve- midway between upper and lower borders, between pons and
Cerebella peduncle
2. Abducent nerve- between pyramid and pons
3. Facial and vestibulocochlear- cerebellopontine angle
Facial nerve has two roots medial(motor) and nervous intermedius lateral(sensory)

Question 3

External features of midbrain

Answer 3

Ventral aspect
Cerebral peduncle/ crux cerebri
Oculomotor nerve- exit from interpeduncular fossa

Question 4

Cerebello-pontine angle contents

Answer 4

1. Facial, vestibulocochlear and glossopharyngeal nerves
2. Foramen of luschka and the lateral recess
3. Choroid plexus
4. Anterior inferior cerebellar artery

Question 5

Discuss midbrain

Answer 5

Cerebral aqueduct- divides midbrain into posterior(tectum) and anterior (cerebral peduncle)
Tectum: 4 coliculi and trochlear nerve
Cerebral peduncle: anterior to posterior
-crus cerebri
- substantia nigra - nerve cells contain melanin pigment, and dopamine secreting neurons
- tegmentum- contains cranial nerve nuclei. Red nuclei, Oculomotor nucleus
Interpeduncular fossa - between the two peduncles, Oculomotor nerve exits

Question 6

Boundaries and contents of interpeduncular fossa

Answer 6

Boundaries
1. Anterior- optic chiasma
2. Posterior- pons
3. Lateral- crus cerebri and optic tract

Contents
1. Tuber cinereum
2. Pituitary gland
3. Mammillary bodies
4. Posterior perforated substance
5. Oculomotor nerve

Question 7

Tracts passing through the pons

Answer 7

1. Descending corticospinal tracts – responsible for voluntary motor control of the body.
2. Descending corticobulbar tracts – responsible for voluntary motor control of face, head and neck.
   3.Ascending medial lemniscus tracts – responsible for fine touch, vibration and proprioception.
3. Ascending spinothalamic tracts – responsible for pain and temperature sensation

Question 8

Discuss 4th ventricle

Answer 8

Cavity of hindbrain
Located behind pons and upper part of medulla, in front of cerebellum

Rhomboid in shape with 4 angles:
Superior angle- continuous with cerebral aqueduct
Inferior angle- continuous with central canal
Lateral angles- lateral recess and foramen of luschka

Boundaries:
-lateral- superior cerebellar peduncle
-middle- lateral recess
-inferior- inferior cerebellar peduncle
-roof- superior medullary villum, part of the cerebellum and inferior medullary villum
- floor- pons and upper part of medulla
Foramen:
-Foramen of magendie
- foramen of luschka
- lateral recess

Communications
1. With subarachnoid space by Foramen of magendie and Foramen of luschka
2. With 3rd ventricle by cerebral aqueduct
3. With central canal of spinal cord