This is a power point on the first four cranial nerves. Their path area innervated and clinical application of each nerves. this is prepared for group presentation.

1. Trochlear
nerve
Optic
nerve
Olfactory
nerve
Oculomotor
nerve
Group members
Abenezer Bogale
Fisseha Mulugeta
Rebecca Shisema

2. Outline
• Origin
• Course
• Special features
• Clinical Significance

3. Origin
-Arises from olfactory epithelium of the upper part of
the nasal cavity as olfactory fascicles where it takes the
olfactory information from the environment.
Olfactory Nerve

4. Course
-After arising as olfactory fascicles travel up in
to the the cribriform plate of the ethimoid bone
-Come together as olfactory bulb. In the
olfactory bulb the fibers from the nasal mucosa
will join with mitral dendrites found on the bulb.
-After they come together in the olfactory bulb
they will become olfactory tract
-It goes to anterior perforated substance and
divide to medial and lateral olfactory striae.

6. Special features
• It is purely sensory nerve (special visceral
afferent
• is one of the two nerves that do not arise from
the brain stem
• Shortest of the 12 cranial nerves.
• As it originates from olfactory placode it is the
only cranial nerve that has ability to
regenerate

7. Clinical Significance
Anosmia
• Damage to this nerve may lead to the state of
inability to smell or anosmia.
• But inability to smell is not only caused by
nerve damage but may be due to blunt
trauma, tumor of the frontal lobe,
Menningitis,Covid-19

8. Optic Nerve
It is a paired nerve arising from the ganglion
layer of the retina.
Origin

9. Course
• It leaves the eye after converging in the optic
disc
• Goes to the optic chiasm then ascends as
optic tract to the lateral geniculate nucleus.
• Then to the pretectal nucleus and superior
colliculus.
• In the optic chiasm it will cross with the contra
lateral optic nerve fiber.

10. Special features
• It is purely sensory nerve and its nucleus do not
arise from the brain stem.
• Unlike any other cranial nerve its is lined by
oligodendrocytes rather than Schwann cells which
makes it part of the central nerves system and
susceptible to diseases affected the central
nervous system such as multiple sclerosis.
• The optic nerve is ensheathed in all
three meningeal layers (dura, arachnoid, and pia
mater) rather than the epineurium, perineurium,
and endoneurium found in peripheral nerves

11. Clinical Significance
-Visual loss from the nerve damage depends on
the location of the damage.

12. Occulomotor Nerve
Origin
-It starts from the midbrain in the anterior part
from its nucleus
-Goes to the eye orbit via superior orbital fissure
-Innervates extrinsic eye muscles that enable
most movements of the eye and that raise the
eyelid.

13. Course
• After arising from its nucleus from the mid
brain it goes lateral to the cavernous sinus. In
the cavernous sinus it divides into:-
-Superior:- for sup. rectus & levator
palpebrae superioris
-Inferior:- for inferior & medial rectus,
inferior oblique

15. Special features
-It is purely motor nerve and it is one of the
nerves that arises from the brain stem
-Has characteristics of both general somatic
efferent and general visceral efferent.
-Contain parasympathetic fibers arising from
Edinger Westephal nuclei to sphincter pupilae
and ciliary muscles

16. Clinical Significance
Caused by
 DM
 Hypertension
 Demyelinating
diseases

17. Trochlear nerve
Origin
-It arises from the back of the mid brain and
comes in front of the brain stem to supply the
superior oblique muscle
Course
• Has same path with the cranial nerve III and it
goes to the orbit via superior orbital fissure.

18. Special features
The smallest cranial nerve in route. It runs the
longest intracranial route. Emerges from the
posterior wall of midbrain

19. Clinical Significance
 Results in diplopia
and inability to
rotate the eye
inferolateral.
 So the eye deviates
upward and slightly
inward.
 Person has difficulty
in walking
downstairs.

20. Sources and reference
Snell’s Neuroanatomy 7th edition
Netters atlas anatomy