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1. Cranial Nerves
By Dr. Ann Mwangi
Department of Human Anatomy
JKUAT

2. Cranial Nerves
•Theyare a set of 12 paired nerves of the peripheral
nervous systemthat connect brain to different parts
of head, neck;
1. CN (I)-Olfactory
2. CN(II)-Optic
3. CN(III)-Oculomotor
4. CN(IV)-Trochlea
5. CN(V)-Trigeminal
6. CN(VI)-Abducens
7. CN(VII)-Facial
8. CN(VIII)-Vestibulo-cochlea
9. CN(IX)-Grosso-pharyngeal
10. CN(X)-Vagus
11. CN(VI)-Accessory
12. CN(XII)-Hypoglossal
They arise/emerge directly from the brain and exit through the
foramina and fissures in the bones of the cranium

3. Bones of the skull (cranium)
-Has 2 sets of bones
•Neurocranium-Bones of the
calvariaand base of the skull-8
bones
•Viscero-cranium-Facial bones-
14 bones
-Bones are joined by sutures
•Only the mandibleis attached by a
freely movable joint

5. (Anterior and Lateral View)
Figure 5.11

6. Inferior View
Figure 5.9

7. Superior View/ Base of the skull

8. Fossa at the base of the cranium

10. •Cranial Nerves are functionally divided into three;
Motor Nerves (3,4,6,11,12)
Sensory Nerves (1,2,8)
Mixed nerves(5,7,9,10)
1. CN (I)-Olfactory-Sensory
2. CN(II)-Optic-Sensory
3. CN(III)-Oculomotor-Motor
4. CN(IV)-Trochlea-Motor
5. CN(V)-Trigeminal-Mixed
6. CN(VI)-Abducens-Motor
7. CN(VII)-Facial-Mixed
8. CN(VIII)-Vestibulo-cochlea-Sensory
9. CN(IX)-Grosso-pharyngeal-Mixed
10. CN(X)-Vagus-Mixed
11. CN(VI)-Accessory-Motor
12. CN(XII)-Hypoglossal –Motor

11. Cranial nerves and their
location in the brain
1.CN (I)-Olfactory-inferior surface
of frontal lobe
2. CN(II)-Optic-midbrain
3. CN(III)-Oculomotor-midbrain
4. CN(IV)-Trochlea-dorsal midbrain
5. CN(V)-Trigeminal-lateral aspect of
mid pons

12. 6. CN(VI)-Abducens-Pons
(pontomedullaryjunction)
7. CN(VII)-Facial-Pons (cerebellopontine
angle
8. CN(VIII)-Vestibulo-cochlea-Pons (Lateral
to facial nerve)
9. CN(IX)-Grosso-pharyngeal-Medulla
10. CN(X)-Vagus-Medulla
11. CN(VI)-Accessory-Medulla
12. CN(XII)-Hypoglossal -Medulla

14. Cranial nerve (CN-0) -Nervus Terminalis/
Terminal nerve
•It was first found in humans in 1913.
•Its unofficially by other names, including cranial nerve
XIII
•The nerve is often overlooked because it is unusually
thin for a cranial nerve, and is often torn out upon
exposing the brain.
•Carefuldissectionis necessary to visualize the nerve.
•Its very close to olfactory nerveandoften confused for
its branch, but its not connected to theolfactory bulb
•Hypothesis suggest that it is involved in sensing
ofpheromones (substances secreted and received by same
species), hence related regulatingsexualbehaviours

15. Cranial nerve (CN-I) –olfactory
(sensory)
•Origin-roof of nasal cavity
•To-cerebral (temporal lobe).
•Enterstheskullvia the cribriform plate of
ethmoid bone
•Sensory function: olfaction (smelling)
Course
•Inhalation;
•Olfactory epithelium(roof of the nose)
•Receptors generate impulse-move to
olfactory bulb through cribriform foramina
•Passthro’olfactory tract (frontal lobe)
•To association areas (temporal lobe)

17. Cranial Nerve (CN-II) –Optic (sensory)
•Origin-Optic disc in the retina, that capturers photons (rays)
•To-Visual cortex (occipital lobe)
•Entertheskullvia the optic canal
•Sensory function:transmission of visual information from
theretinato the vision centres of thebrain
Course
•Light enters the eyes
•Arepicked by special receptors in theretina(rods and
cones-photoreceptors)
•They travel thro’ optic nerve (via optic canal)
•-the 2 optic nerves forms optic chiasma (decussation)-
picked by 2 optic tracts-to relay nucleus (lateral geniculate
body) in the thalamus
•Travel tothe visual cortex (occipital lobe-area 17 for visual
processing )

18. Cranial nerve (CN-III) –
oculomotor (Motor)
•Origin-From the tegmentum of the
midbrain at the level of (superior colliculus)
•Exits-midbrain from the interpeduncular
fossa and enters the orbit via the superior
orbital fissure.
•Motorfunction:
Muscle function-Provides a motor function
to muscles around the eyes; levator palpebrae
superioris, superior rectus, medial rectus,
inferior rectus, and inferior oblique muscles
(muscles help the eyes move and focus on
objects).

19. Cranial nerve (CN-IV) –
Trochlea (Motor)
•Origin-Trochlea nuclei in medial midbrain
( level of Inferiorcolliculus)
•Is the smallest cranial nerve with the
longest intracranial courseand the
only nerve to have a dorsal exit from
the brainstem
•Exitstheskullvia the superior
orbital fissure
•Motorfunction-Eye movement,
Innervation of thesuperior
obliquemuscleresponsible for
downward, outward, and inward eye
movements.

20. Cranial nerve (CN-V) –Trigeminal
(Mixed)
•Location -Is the largest cranial nerve extending
fromthe midbrain to the medulla.
•Originates from three sensory nuclei
(mesencephalic nuclei, principal sensory nuclei
and spinal nuclei of trigeminal nerve).
•Has three divisions:
V1; Ophthalmic division
•Sends sensory information from the upper part
of theface, including forehead, scalp, upper
eyelids andnose
•Enter theskullvia -the superior orbitalfissure

21. V2; Maxillary division
-This division communicates
sensory information from the
middle part of the face, including
lower eyelid, cheeks, gums of
upper jaw, palate, upper lip, teeth,
nasal cavity, palate, and tonsils
•Enter theskullvia the foramen
rotundum

22. V3; Mandibular division
-Has both a sensory and motor
functions.
•It sends sensory information
from teeth, gums of the
lowerjaw, chin, buccal mucosa,
dorsum of thetongue,
andexternal acoustic meatus
•Motor innervation is to the
muscles of mastication
(temporalis, masseter, medial and
lateral pterygoids)
•Exits theskullvia the foramen
Ovale

24. Cranial nerve (CN-VI) –
Abducens(motor)
•Origin-abducensnucleus
(pontomedullary junction).
•Exitstheskullvia Superior
orbital fissure
•Motorfunction-lateral rectus
muscle-abduct the eyeball

25. Cranial Nerve (CN-VII) –Facial
(Mixed)
•Origin-Pons (cerebellopontine angle)
•Exitsvia the Internal acoustic meatus
through facial canal then through
stylomastoidforamen
•Motor–musclesoffacialexpression.
•Sensory–theexternalauditorymeatus,
thetympanicmembrane,andthepinna
oftheear.
•SpecialSensory–providesspecialtaste
sensationtotheanterior2/3ofthetongue
viathechordatympani

26. Cranial neve (CN –VIII)
vestibulocochlear (Sensory)
•Location-Pons (lateralto the facial
nerve)
•Enters theskull-via the internal auditory
meatus
•Vestibular nerve:
•Regulation of thehair cellsof
thesemi-circular canals for the
adjustment of spatialposition
•Transmission of impulses for the
sense of balance
•Cochlear nerve:
•Regulation of thehair cellsof
theorgan of Cortifor the
adjustment ofsensitivityregarding
sound waves
•Transmission of impulses for hearing

27. Cranial nerve (CN-IX)
glossopharyngeal(Mixed)
•Origin-Medulla oblongata
•Exitstheskullvia the-jugular foramen
•Sensory:Innervatestheoropharynx,carotid
bodyandsinus,middleearcavityand
Eustachiantube.
•Specialsensory:Providestastesensationto
theposterior1/3ofthetongue.
•Motor:Innervatesthestylopharyngeus
muscleofthepharynx
•Parasympathetic:Providesparasympathetic
innervationtotheparotidgland.

28. Cranial Nerve (CN X) vagus (Mixed)
•Origin-Medulla oblongata
•Exitstheskullvia the jugular foramen
•Sensory:Innervatestheskinoftheexternal
acousticmeatusandtheinternalsurfacesofthe
laryngopharynxandlarynx.
•Providesvisceralsensationtotheheartand
abdominalviscera.
•SpecialSensory:Providestastesensationtothe
epiglottisandrootofthetongue.
•Motor:Providesmotorinnervationtothe
majorityofthemusclesofthepharynx,soft
palateandlarynx.
•Parasympathetic:Innervatesthesmoothmuscle
ofthetrachea,bronchiandgastro-intestinaltract
andregulatesheartrhythm

29. Cranial nerve (CN-XI) Spinal and
cranial accessory)(Motor)
•Origin-Medulla
•Motor function: Sternocleidomastoid,
Trapezius and muscles of Larynx and
Pharynx
•Exits-theskullvia the jugular foramen
Cranial roots
•Originate from nucleus ambiguus
•Join the spinal roots to exit the jugular
foramen
•Join the vagus nerve and distribute to the
muscles of pharynx and larynx
Spinal roots –C1, C2, C3.
•Originate from spinal nucleus of accessory
nerve
•Ascend through the foramen magnum and
exit the cranium through the jugular
foramen
•Innervate the sternocleidomastoid and
trapezius muscles

30. Cranial nerve (CN-XII
(hypoglossal)(Motor)
•Origin-hypoglossal nucleus in the
medulla oblongata.
•Motor function-movements of
thetongue
•Exitstheskullvia-the hypoglossal
canal, ending at the base and
underside of thetongue.