1. Anatomy of the Brain Stem
NEUROANATOMY
Lecture : 3
Anatomy of the Brain Stem
Prepared and presented by:
Dr. Iyad Mousa Hussein,
Ph.D in Neurology
Head of Neurology Department
Nasser Hospital

2. LECTURE OBJECTIVES: 1. Morphological Subdivisions of the Brain.
2. Site, Parts, and Functions of the Brain Stem.
3. Parts of the Medulla Oblongata.
4. Connection, External, and internal Features of the Medulla Oblongata.
5. Connection, External, and internal Features of the Pons.
6. Connection, External, and internal Features of the Midbrain.
7. Location, Connections, and Functions of the Reticular Formation of the Brain Stem.
8. Motor and sensory pathway.

3. Morphological Subdivisions of the Brain
The Cerebrum: formed of right and left cerebral hemisphere.
2. The Cerebellum: below the posterior part of the
cerebrum.
3. The Brain Stem: formed of the following parts (from
downward):
a. Medulla oblongata.
b. Pons.
c. Midbrain.

4. The Brain Stem downward):
The brain stem lying infront of the cerebellum and
occupies the posterior cranial fossa.
The brain stem formed of the following parts (from
downward):
1. Medulla oblongata.
2. Pons.
3. Midbrain.

7. Functions of the Brain Stem
1. It serves as a conduit for the ascending and
descending tracts.
2. It contains important reflex centers associated with the control of cardiovascular, respiratory systems and consciousness.
3. It contains the important nuclei of cranial nerves III through XII.

8. The Medulla Oblongata
The medulla oblongata is the lower part of the brain
stem (3 cm).
Extent:
Above: it is continuous with pons.
Below: it is continuous with the spinal cord at the
foramen magnum.

11. Parts of the Medulla Oblongata
Closed Medulla: it is the lower half of the medulla,
as it encloses a central canal continuous with that
of spinal cord.
Open Medulla: it is the upper half of the medulla,
as it opens into the fourth ventricle.

13. External Features of the Medulla Oblongata
A. Anterolateral Surface:
1. The anterior median fissure.
2. The pyramid: formed by the pyramidal
(corticospinal) tract.
3. The olive: formed by the inferior olivary nucleus.
4. The anterolateral sulci: gives exit to the hypoglossal nerves.
5. The posterolateral sulci: gives exit to the
glossopharyngeal, vagus and cranial accessory nerves.
6. The inferior cerebellar peduncle.

16. B. The posterior surface of the medulla oblongata:
1. The posterior surface of the upper half (open
medulla): presents the following features from
medial to lateral:
a. The median longitudinal fissure.
b. Inferior fovea.
c. Hypoglossal trigone (triangle).
d. Vagal trigone.
e. Vestibular trigone.
2. The posterior surface of the lower half (closed
a. Posterior median fissure.
b. Gracile tract.
c. Cuneate tract.

18. Internal Structures of the Medulla Oblongata
The main nuclei of the medulla oblongata:
1. Gracile nucleus: proprioceptive and fine touch
from the lower 1/2 of the body.
2. Cuneate nucleus: proprioceptive and fine
touch from the upper 1/2 of the body.
3. Inferior olivary nucleus: extrapyramidal function.
4. Inferior salivary nucleus: parasympathetic
function via the glossopharyngeal nerve.

19. 5. Spinal nucleus of trigeminal nerve: pain and
temperature sensations from the face and scalp
via the trigeminal nerve.
6. Solitary nucleus: taste sensations via the facial,
glossopharyngeal and vagus nerves.
7. Nucleus ambiguous: pyramidal and
extrapyramidal functions via motor fibers of the
glossopharyngeal, vagus and accessory nerves.
8. Dorsal nucleus of vagus nerve: parasympathetic
via the glossopharyngeal and vagus nerves.
9. Hypoglossal nucleus: motor function of the
tongue via hypoglossal nerve.

21. Blood Supply of the Medulla Oblongata
The medulla oblongata is supplied by:
The vertebral arteries.
The anterior spinal artery.
The posterior spinal arteries.
The posterior inferior cerebellar arteries.
The basilar artery.

24. The Pons
Extent: it extends from the medulla oblongata below to midbrain above and lies infront of the cerebellum.

26. External features of the pons
A. The anterior surface of the pons: presents the following features:
1. The basilar groove: for basilar artery.
2. The transverse streaks: to form middle cerebellar peduncle.
3. The middle cerebellar peduncle.
4. The trigeminal nerve.
5. The abducent nerve.
6. The facial nerve.
7. The vestibule-cochlear nerve.

29. B. The posterior surface of the pons: presents the following features:
1. The median longitudinal sulcus: the middle line.
2. The medial eminence: produced by the abducent
nucleus.
3. The facial colliculus: it produced by the facial nucleus.
4. The medullary stria: transverse nerve fibers
which separate the posterior surface of pons from
that of medulla oblongata.
5. Superior fovea.

32. Internal structures of the pons
Pontine nuclei: they form part of the cortico-ponto-
cerebellar pathway.
2. Transverse fibers: pontocerebellar fibers.
3. Longitudinal fibers: which include pyramidal and cortico-
pontine fibers.
4. Nuclei of the trigeminal nerve:
a. Motor nucleus.
b. Sensory nucleus.
5. Nucleus of the abducent nerve.
6. Nuclei of the facial nerve:
Motor nucleus.
b. Superior salivary nucleus: parasympathetic function.

33. 7. Nuclei of the vestibulocochlear nerve.
8. Lateral lemniscus: it is a band of ascending fibers
carrying hearing impulses from both ears.
9. Spinal lemniscus: it is a band of ascending fibers
carrying pain, temperature and crude touch from the
opposite side of the body below the head.
10. Trigeminal lemniscus: it is a band of ascending
fibers carrying pain, temperature and touch and
proprioception from the opposite side of the face and scalp.
11. Medial lemniscus: it is a band of ascending fibers
carrying proprioceptive and fine touch from the opposite
side of the body below the head.

35. Blood Supply of the Pons
The pons is supplied by:
The anterior inferior cerebellar arteries.
The superior cerebellar arteries.
The basilar artery (gives pontine arteries).

37. Thank You