Download 05. brain stem

Stalk Like. 
Connects: 
Narrow Spinal Cord with the
Expanded Fore Brain.
Occupies: 
Posterior Cranial Fossa. 
Lies Against: 
Basilar part of Occipital 
Bone.
Largely Covered by: 
Cerebellum.
MID
BRAIN
MEDULLA
OBLONGATA
PONS
BULB. 
Entering Fibers: 
Cortico Bulbar. 
Syndromes Associated:
Pseudo Bulbar Palsy. 
Bulbar Palsy. 

(1) A conduit for: 
Ascending and Descending 
tracts between the Spinal
Cord and the Higher Centers
in the Forebrain.
(2) Contains: 
A. Cranial Nerve Nuclei 
(111-x11).
B. Reflex Centers for 
Respiratory and
Cardiovascular systems.
(3) Controls over:
Level of Consciousness
The Ventral Median
Fissure
Divides it into Two
Halves.
Each Half Presented
the following :



A Longitudinal Elevation
along the side of the
fissure.
The pyramids are 
composed of:
Bundles of Nerve Fibers
(Corticospinal).
They originate from 
Large Nerve Cells in the
Motor Cerebral Cortex.


The Pyramids Taper 
Inferiorly.
The Majority of the 
Descending Fibers
(75-90%) Cross Over
to the opposite side.
They form
Decussation of the 
Pyramids.
It partially obscures 
the ventral fissure.
Oval Elevation.
Lateral to the Upper Part
of the Pyramid.
Produced by
The underlying Inferior
Olivary Nucleus
It is Important in the
Control of Movement.

1. Hypoglossal (12TH) 
nerve:
Between the Pyramid 
and Olive.
2. Glossopharyngeal, 
Vagus and Cranial part
of Acessory (9, 10
and11TH) nerves :
Between the Olive and 
the Inferior Cerebellar
Peduncle.
The Anterior surface is 
Convex from side to side.
It shows: 
Basilar Sulcus : 
A Median Groove which 
lodges the Basilar Artery.
Many Transverse 
Pontocerebellar Fibers.
They are collected Laterally
to form the Middle
Cerebellar Peduncles.

1. Trigeminal (5th) 
nerve:
Attached to the side of
the Pons near its upper
border.
It has Two Roots: 
Large Sensory. 
Small Motor. 
Motor root is Antero 
Medial to the Sensory
root.

2. Abducent (6th) nerve: 
Between the Lower 
border of the Pons and
the Pyramid.
3. Facial (7th) nerve : 
Between the Lower 
border of the Pons and
the Inferior Cerebellar
Peduncle.
4. Vestibulo cochlear (8th)
nerve :
Lateral to the Facial . 
The vestibular nerve is 
anterior to the cochlear.

It is the : 
Massive Basis 
Pedunculi (Crura
Cerebri).
The Crura are made
by:
Corticobulbar. 
Corticospinal Fibers.

Separates the Cerebral
Peduncles.
Boundaries: 
Inferiorly : 
Pons. 
Anteriorly : 
Optic Chiasma. 
Laterally: 
Optic Tracts . 
Posterolaterally: 
Cerebral Peduncles. 

Oculo motor (3rd) 
nerve :
At the medial side of
the cerebral
peduncle.

Closed (Lower) Medulla
It is the Continuation of
the Posterior Surface of
the Spinal Cord.
Posterior Median Sulcus
divides it into two
halves.


Gracile Tract: 
A Longitudinal Column on both
sides of the Median Sulcus.
Superiorly: 
It expands. 
It ends in the Gracile Tubercle
(produced by the underlying
(Gracile Nucleus).
Cunate Tract and Tubercle : 
Lateral to the Gracile Tract and
Tubercle respectively.
Forms the Lower 1/3 of 
the Floor of the Fourth
Ventricle.
Divided by the Median 
Sulcus into two halves.
Has an inverted (V) 
Shaped Depression
(Inferior Fovea).
The Fovea separates: 
Motor nuclei (Medial) from
Sensory nuclei (Lateral).
Medial : 
Hypoglossal Nucleus. 
Lateral : 
Vestibular Nucleus. 
At the Fovea : 
Nuclear Complex 
(Glossopharyngeal
and Vagus nerves).
The Fovea represents 
the Sulcus Limitans of
the Spinal Cord.
Forms the Upper 2/3 of the 
Floor of the 4th Ventricle.
Hidden by the Cerebellum. 
Widest at the Pontomedullary
junction.
Lateral Aperture (Foramen of
Luschka):
Allows passage of CSF from 
the 4TH ventricle to the
Subarachnoid space around
the brain.


Divided into Symmetrical Halves
by the Median Sulcus.
Medial Eminence: 
An Elongated Elevation Lateral 
to the Sulcus.
Facial Colliculus: 
The Inferior Expanded end of 
the Eminence.
Produced by the fibers of the 
Facial Nerve winding around the
Abducent Nucleus.
Vestibular Area 
Lateral to the Medial
Eminence.
Produced by the 
underlying
Vestibular Nuclei.

Corpora Quadregimina
Four Rounded Colliculi
Divided into Superior
and Inferior Pairs.
Superior Colliculi: 
Centers of Visual
Reflexes.
Inferior Colliculi: 
Lower Auditory
Centers.
The Cerebral 
Aqueduct traverses
through the length of
the mid brain.

Trochlear Nerve 
It is the Only cranial 
nerve that can be
identified in the dorsal
aspect of brain stem.
It emerges in the 
midline.
Caudal to the Inferior 
Colliculs.
Superior. 
Middle. 
Inferior Peduncles. 
Connect Cerebellum
to :
Mid brain. 
Pons. 
Medulla. 

Middle . 
Inferior Cerebellar
Peduncles.
Olive. 
Pyramid. 
Attached Cranial 
Nerves.
