Download 4 th Cranial nerve

Cranial nerves: Are 12 pairs of nerves connected directly to the brain (to the
brain stem) except the 1st pair.
Theses nerves characteristic by :
1-it not has two roots like spinal nerves.
2-Some are sensory ,some are motor and some are mixed.
3-All the cranial nerves enervated the head except the vagus extended to the
thoracic and abdomen .
Functional compound of the cranial nerves :
1-The somatic and visceral efferent impulses .
a-The general visceral efferent fibers carry motor impulses to skeletal muscles .
b-The general visceral efferent fibers ( autonomic ) supply glandular tissue and
smooth muscles.
2-The somatic and visceral afferent impulses :
a-the general visceral afferent fibers ( interceptive ) convey impulses from
visceral , gland , blood vessels and mucous membrane.
b-The general somatic afferent fibers ( incoming ) : transmits impulses which
receive stimulation outside world and supply the body with information
concerning its environment.
3-The special visceral efferent ( SVE ) fibers : which supply the muscles
derived embryologically from and related to the branchiomeres and theses
muscles are striated and are mainly associated with visceral activities of the
digestive and respiratory system.
4-The special visceral afferent ( SVA ) fibers: are the fibers which
innervated taste buds and olfactory mucosa .
4- The special somatic afferent ( SSA ) fibers : the vision , hearing and
equilibrium are special sense relate to somatic activities .
The cranial nerves are :
I. 1ST cranial nerve : Olfactory nerves are sensory for smelling .
II. 2nd cranial nerve : Optic nerves are sensory for sight .
III. 3rd cranial nerve: Oculomotor nerves are motor for movement of eye muscles
.
IV. 4th cranial nerve: Trochlear nerves are motor for movement of obliqus
dorsalis muscle of eye .
V. 5th cranial nerve : Trigeminal nerves are mixed nerves .
VI. 6th cranial nerve : Abducent nerves are motor nerve for the movement of
rectus lateralis and retractor oculi muscles of eye .
VII. 7th cranial nerve : facial nerves are mixed .
VIII. 8th cranial nerve : Auditory nerve or vistibulocochlear nerve are sensory
responsible for hearing and balance .
IX. 9th cranial nerve glossopharyngeal nerve are mixed .
X. 10th cranial nerve : Vagus nerves are mixed .
XI. 11th cranial nerve :Accessory nerves are motor for movement of
brachiocephalicus and trapizeus muscles.
XII. 12th cranial nerve :Hypoglossal nerves are motor for the movement of
lingual muscles.
1ST Cranial nerve ( Olfactory nerves):
1-the olfactory nerves of smell are represented by a number of bundles of nerve
fibers in mucous membrane of dorsal concha and nasal septum .
2-it passes the foramina of cribriform of the ethmoid bone.
3-they end in the olfactory bulbs where they synapse .
4-the fibers not connect with brain stem .
5- They are not having ganglion .
2nd Cranial nerve : Optic nerves are sensory for sight .
a- Its arise from ganglion layer of the retina (ganglion cell layer). The nerve
fibers of retina converge towards the optic papillae or disc as special somatic
afferent fibers and pierce the choroids and sclerotic coat to emerge as the
optic nerve.
b- The nerve course caudally toward the brain and passes through the optic
canal and joins the opposite nerve to form the optic chiasma.
c- From the optic chiasma the fibers are continued in the optic tract to lateral
geniculate bodies and mid brain.
d- The number of nerve fibers in the optic nerve is related to importance and
activity of the visual system in particular species.
3rd Cranial nerve: Oculomotor nerves:
aAre motor nerves to the ocular muscles and supply all the muscle of the
eye except the obliqus dorsalis, rectus lateralis and retractor oculi.
b- It also contains autonomic fibers for the ciliary muscles .
c- It arise b from the brain stem medial to the cerebral crura.
d- It leaves the cranial cavity by way of the orbital fissure.
e- It divided into two branches :
1-The dorsal branch –supply the rectus dorsalis and levator palperbal
superioris
2-The ventral branch—supply the ciliary ganglion and rectus medialis ,
ventralis and obliqus ventralis muscles of eye
4th Cranial nerve: Trochlear nerves
A-are motor for movement of obliqus dorsalis muscle of eye .
b- is the smallest of the cranial nerves , it arise from the rostral cerebral
peduncle caudal to the caudal colliculus .
c- It is only cranial nerve to emerge from the dorsal surface of the brain stem.
d- It leaves the cranium cavity through a small foramen immediately above the
orbital fissure or through the orbital fissure .
5th Cranial nerve : Trigeminal nerves are mixed nerves .
a- It is connected with the lateral part of pons by large sensory root and
smaller motor root.
b- The sensory root connected with large trigeminal ganglion( semilunar
ganglion ) which occupy the rostrolateral part of foramen lacerum , then
from the rostral face of this ganglion arise three division ( ophthalmic ,
maxillary and mandibular nerves )
c- The motor root extends rostrally beneath the sensory root and the trigeminal
ganglion , it is incorporated with the mandibular nerve.
d- The trigeminal nerve divides into three branches( ophthalmic , maxillary and
mandibular ( have two root sensory and motor ).
A-Ophthalmic nerve:
a- is the smallest of the three branches.
b- Its purely sensory .
c- It arise from the from the medial part of the rostral part of the trigeminal
ganglion.
D-it leaves the cranium cavity through the orbital fissure with third and 6 th
cranial nerve and divides into three branches
1- Lacrimal nerve –supply the lacrimal gland and upper eyelid.
2-Zygomaticotemporal branch –it arise alone or with the lacrimal by common
trunk, it supply the skin of the temporal region. In ruminant (in horned animals )
most of fibers of it course toward the horn as the corneal branches terminated in
the lateral caudal surface of the base of horn and emerges from the zygomatic
process of the frontal bone.
3-Frontal nerve : runs rostrally almost parallel with the obliqus dorsalis ,
within the orbital , then pass through the supraorbital foramen as the
supraorbital nerve( with artery ), then ramifies in the skin of the forehead and
upper eyelids .
4-Nasociliary nerve : pass rostrally and medially under the rectus dorsalis
muscle and divided into two branches
a-the ethmoid nerve : which is the continuation of the trunk inter the nasal
cavity through the ethmoid foramen and ramifies in the mucous of the nasal
septum and dorsal nasal concha .
b-Infratrochlear nerve : ramifies in the skin nasal cavity ,it gives branches to
the conjunctiva , lacrimal caruncle , Long Branch to the 3 rd eyelid and lacrimal
duct and sac.
B-Maxillary nerve :
1-it purely sensory and is much larger the ophthalmic .
2-it extends from the trigeminal ganglion in the middle cranial fossa in the large
maxillary sulcus of the basisphenoid bone .
3- It emerges through the foramen rotundum and is continued in the infraorbital
canal. It divides into follows :
a-Zygomaticofacial branch—arise before the maxillary nerve reaches the
pterygopalatine fossa, it pierce the periorbital and divided into two branches and
ramify chiefly in the lower eyelid and the adjacent skin.
B-Pterygopalatine nerve –is given off in the pterygopalatine fossa , it is broad
and flat , and have several small ganglion. It divided into three branches.
1-Caudal nasal –enter the nasal cavity and divided into : ( medial branch to the
mm of the nasal cavity , vomeronasal organ and hard palate; lateral branch to
the mm and divided into the ventral nasal concha and to the middle and ventral
nasal meatus.
2-Greater palatine nerve – is the largest branch, runs in the greater palatine
canal and palatine groove , ramifies in the hard palate and gums.
3-lesser palatine nerve – is the smallest branch and ramifies in the soft palate.
4-Infraorbital nerve : is the continuation of the maxillary trunk , it passes the
infraorbital canal and emerges through the infraorbital foramen and divided into
(1- external nasal branch-supply nose , 2- internal nasal branch –supply upper
and lower lips and nostrils, 3- maxillary labial branch –supply lip and cheeks
and 4- along it course in the canal gives off maxillary alveolar branch which
supply the teeth and alveolar peroisteum and gums )
B-Mandibular nerve :
a- it formed by union of the two roots ( the large sensory) comes from the
trigeminal ganglion and the motor root is the smaller part .
b- It emerges from the cranium cavity through the oval notch of the foramen
lacerum and passes between the wing of the basisphenoid bone and the
muscular process of the petrous part of the temporal bone and when reaches to
the lateral surface of the pterygoideus medialis muscle divided into two terminal
branches (mandibular alveolar and lingual nerves).
The mandibular nerve gives the following branches
1-the masseter nerve –ramifies the masseter muscle .
2-deep temporal nerve—two or three in number , supply the temporal muscle.
3-Buccal nerve-it continuous rostral in the submucous tissue of the cheek along
the ventral border of the depress or labii mandibularis and divided into branches
ramify I the mm and gland of the lip in the lip commissure.
4-auriculotemporal nerve : pass between the parotid gland and the neck of the
ramus of the mandible , turn around it and divided into two branches (the
transverse facial branch –ramify in the skin of cheek , the rostral auricular
branch )
5-mandibular alveolar nerve :arise with the lingual nerve by common trunk ,
then the two separated at the acute angle and the mandibular branch enter the
mandibular foramen and course in the mandibular canal ,it emerges at the
mental foramen as the mental nerve which terminating by divided into six to
night mandibular labial and mental branch , which ramify in the lower lip and
chin. Before enter the mandibular canal it gives the mylohyoid nerve , which
supply the mylohyoid m and inside the canal gives the mandibular alveolar
branches supply the teeth .
6- Lingual nerve : arise by common trunk with the mandibular alveolar nerve
after separating directly toward the root of the tongue and give the sublingual
nerve which supplies the mm of the tongue and the floor of the mouth.
Note: The choradatympani: branch of facial joins the lingual nerve at the
origin of the lingual.
6th cranial nerve: Abducent nerves
a- Are motor nerve.
b- arise from the brain stem behind the pons directly lateral to the pyramid ,
c- Cranially pierce the dura mater with 3rd cranial nerve and ophthalmic nerve
and leaves the cranium cavity through the orbital fissure.
d- In the orbit divided into two branches to rectus lateralis and retractor oculi
muscles of eye.
7th cranial nerve: Facial nerves are mixed nerve.
1- Arise superficially from the lateral part of the trapezoid body behind the
pons,
2-the facial nerve enter the internal acoustic meatus with the vesibulocochlear
nerve at the base of the meatus separated from each other and facial nerve pass
through the facial canal.
3-inside the canal , the nerve has an curvature called the knee and above the
knee the geniculate ganglion are found and the choradatympani originate from
it.
4-it gives many branches inside the canal , then reaches to stylomastoid
foramen.
5-after emerge from the stylomastoid foramen pass between the guttural pouch
and the parotid salivary gland , and receive the auriculotemporal nerve before it
emerge outside .
6-it gives many branches outside the canal before ended by two terminal
branches ( the dorsal buccal and ventral buccal nerves).