Download 06. medulla

1. Traversed by: 
Central Canal.
2. Retains: 
Some of the Features
of the Spinal Cord.
3. Has: 
Motor Decussation. 

Ventral Horn 
Much Attenuated. 
Dorsal Horn 
Replaced by 
Caudal Part of the 
Trigeminal Sensory
Nucleus (Nucleus of the
Spinal Tract of the
Trigeminal Nerve).
It is the Brain Stem 
continuation of:
Substantia Gelatinosa of
the dorsal horn of the
A large nucleus. 
Lies: 
Medial to the Spinal Tract of the 
Trigeminal Nerve.
Extends: 
Through the whole length of the 
brain stem.
Receives: 
Pain and Temperature from: 
Face, Forehead and the Mucous 
Membrane of the Mouth and Nose.
Lies: 
Superficial to its Nucleus. 
Between: 
Cuneate Nucleus and the 
Spino-cerebellar tract.
Formed of: 
Descending fibers that 
Terminate in the
Trigeminal Nucleus Caudal
to the Level of the Pons.
It is: 
Motor Decussation. 
Formed of: 
Pyramidal Fibers 
(75-90%) cross to the 
opposite side.
They descend in the 
Lateral White Column of
the Spinal Cord as the
Lateral Corticospinal
Tract.
Replaced by: 
Spinocerebellar
(Anterior &
Posterior)
Lateral Spino 
Thalamic Tracts.

Small part appear 
Deep to the
corresponding
Gracile and Cuneate
Tracts.
1. Traversed by:
Central Canal.
2. Has: 
Sensory 
Decussation.
3. Pyramids: 
Prominent 

Larger in size. 
Their Axons Form:
Internal Arcuate 
Fibers.
Sensory 
Decussation:
Formed by Crossed
Internal Arcuate
Fibers.


Composed Of: 
Ascending Internal Arcuate
Fibers after their crossing.
Lies: 
Adjacent to the middle line.
Ventral to the Central Canal.
Found in: 
Medulla, Pons and Midbrain.
Terminates in: 
Thalamus. 




Lie: 
Antero lateral to the 
pyramids.
Considered: 
The Inferior Extension 
of the Pontine Nuclei.
Their Axons Form: 
External Arcuate Fibers.
Connected to: 
Cerebellum through the 
Inferior Cerebellar
Formed Of: 
A diffuse mixture of 
Nerve Fibers and Small
Groups of Nerve Cells.
Position: 
Posterolateral to: 
Pyramids.
Ventral to: 
Spinal Tract and Nucleus
of the Trigeminal Nerve.

Lateral to the Cuneate 
nucleus.
Receives 
Unconscious Fibers 
from the Cervical
Region.
Connected to: 
Cerebellum through the
Inferior Cerebellar
Peduncle.

Its Posterior Surface 
Forms:
Lower Part of the Floor 
of the 4th Ventricle.
On Each Side of the
Midline.
Dorsal to 
Medial aspect of the
Pyramids.


Structure: 
A convoluted mass of gray matter.
Has a hilum directed Medially. 
Lies: 
Postero lateral to the pyramids. 
Lateral to the Medial Leminiscus.
Receives Fibers From: 
Motor and Sensory Cerebral 
Cortices.
Red nucleus of the mid brain. 
Corpus Striatum. 
Concerned With: 

(Restiform Body) 
Lies in: 
Dorso Lateral part of the
Medulla.
Connects: 
Medulla and Cerebellum.
Carries: 
Olivocerebellar. 
Vestibulocerebellar. 
Dorsal spinocerebellar. 


Dorsal and Ventral 
Nuclei
Lie: 
Dorsal and Lateral to 
the Inferior Cerebellar
Peduncle.
Receive Afferents 
From:
Cochlear Nerve. 
1. Hypoglossal Nucleus 
A longitudinal column just
lateral to the midline.
2. Dorsal Motor Nucleus of
the Vagus
Lateral to the hypoglossal
nucleus.
Contains: 
Preganglionic 
Parasympathetic fibers as
far as the distal 1/3 of the
transverse colon.



3. Vestibular Nuclei (Complex) 
Consist of 
Medial, Lateral, Inferior and 
Superior Nuclei.
Lie 
In the Lateral Part of the Floor 
of 4th Ventricle.
Inferior Vestibular Nucleus is 
Lateral to the Inferior Fovea.
Receive Afferents From 
Vestibular Nerve.
Lie 
Dorsal to the Inferior 
Olivary Nucleus.
Function 
Gives Motor Fibers to 
Constrictors of the
Pharynx.
Intrinsic Muscles of the
Larynx.

Lies 
Close to the midline. 
Ventromedial to the 
hypoglossal nucleus.
Dorsal to the medial 
lemniscus.
Identified Also in 
Pons, Midbrain and 
Upper Levels of the
Spinal Cord.
Receives Afferents from
Vestibular Nerve. 

Consists of 
Short Ascending and 
Descending fibers.
They connect 
Vestibular and Cochlear
Nuclei with the Cranial
Nuclei (111, 1v and v1)
It serves
Coordination of Head 
and Eye Movements in
Response to VestibuloCochlear Stimuli.

Composed Of the Following
Tracts:
Spinothalamic (Lateral & 
Anterior).
Trigeminothalamic.
Position 
Deeply Placed. 
Lateral to the medial 
leminiscus.
Dorsal to the Inferior 
Olivary Nucleus.
Composed of 
Medial part (well formed in
the medulla) .
Lateral part (well formed in
the pons) .
Solitary Tract is in Between.
Function 
Lateral Nucleus Receives 
Taste Fibers from the Back
of the Tongue.
Medial Nucleus Receives 
(GVA) fibers.



Position 
The Most Caudal Point of 
the Floor of the 4th
Ventricle.
Function 
Site of Action of Centrally 
Acting Emetics.
At Its Site 
Blood Brain Barrier is Lost 
for Certain Chemicals.
Deeply placed. 
Posterior to the 
Olivary Nucleus.
At this level of the
medulla:
It represents as a
Small part of the
system.


Descending: 
Pyramids. 
Tectospinal. 
Ascending: 
Medial leminiscus. 
Spinal leminiscus. 
Trigemino thalamic.
Ventral 
spinocerebellar.


Thrombosis of branches of the 
anterior spinal artery.
Manifested by : 
(1) Contralateral hemiplegia of 
the flaccid type (involvement of
the pyramidal fibers only).
(2) Contralateral loss of 
proprioceptive sensation and fine
touch (affection of medial
lemniscus).
(3) Ipsilateral lower motor lesion
of the hypoglossal nerve
(affection of hypoglossal

Thrombosis of the Inferior
CerebellarArtery.
Manifested by 
(1) Ipsilateral cerebellar 
ataxia.
(2) Loss of Pain and 
Temperature From the
Ipsilateral half of the Face.
(3)Loss of Pain and 
Temperature from the
Contralateral Half of the

(4) Ipsilateral paralysis
of the muscles of the
Palate, Pharynx and
Larynx.
(5) Ipsilateral loss of 
Taste from the
Posterior Third of the
Tongue.
(6) Ipsilateral Horner’s
syndrome

