the cranial nerves outside the skull...the optic nerve (ii cranial nerve) special somatic afferent...
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THE CRANIAL NERVES OUTSIDE THE SKULL
Seminar presented by:
Vicente Aige Gil DVM, PhD
Professor of Veterinary Anatomy
Universidad Autónoma de Barcelona. Spain
For the
Veterinary Neuroscience & Advanced Clinical Neurology/Neurosurgery Course
28th July - 8th August 2014 ECVN /ESVN
Bolognia (Italia)
There are twelve cranial nerves: olfactory nerves (I), optic nerve (II), oculomotor
nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducent nerve (VI), facial
nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus
nerve (X), accessory nerve (XI) and hypoglossal nerve (XII).
Components of the cranial nerves
Functionally, the cranial nerves are classified as motor or sensory. Being each one
somatic and visceral.
The motor component:
The motor fibers that innervate muscles not associated with branchial arches as
the extrinsic muscles of the eye (III, IV and VI cranial nerves); the muscles derived
from the somites as the trapezius, omotransversarius, sternocephalicus and
cleidocephalicus muscles (XI cranial nerve); and the muscles of the tongue, and the
thyrohyoideus and geniohyoideus muscles (XII cranial nerve) form the general
somatic efferent component (GSE).
The motor fibers that innervate muscles associated with branchial arches as
the masticatory, facial, pharyngeal, laryngeal and some hyoideal muscles (V, VII, IX,
X, and XI cranial nerves) form the special visceral efferent component (SVE).
The autonomic nervous system fibers that innervate intrinsic muscles of the
eye, heart, vessels, viscera and glands (III, VII, IX, X and XI cranial nerves) form the
general visceral efferent component (GVE).
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The sensory component:
The sensory fibers coming from the skin and musculoskeletal receptors (V,
VII and X cranial nerves) form the general somatic afferent component (GSA).
The fibers for the sense of sight coming from the retina (II cranial nerve)
and for the senses of equilibrium and hearing coming from the inner ear (VIII
cranial nerve) form the special somatic afferent component (SSA).
The sensory fibers from viscera and heart (VII, IX and X cranial nerves)
make up the general visceral afferent component (GVA). The fibers for the sense of
taste (VII, IX and X cranial nerves) form the special visceral afferent component
(SVA). The sense of smell (I cranial nerve) is also considered an SVA.
It is important to point out that the components of some different cranial
nerves intermingle in order to reach their destinations.
The olfactory nerves (I cranial nerve)
Special visceral afferent (SVA)
The olfactory nerves are formed by unmyelinated axons (surrounded by olfactory
ensheating cells), whose bodies are located in the epithelium that covers half of the
ethmoid labyrinth and the dorsal nasal septum. The axons enter the cranial cavity
through the cribriform plate of the ethmoid bone and reach the olfactory bulb
(paleocortex) of the cerebrum. The olfactory nerves transmit odor sensations.
The vomeronasal organ is closely related to the sense of smell. It has
pheromone receptors to detect odors associated with reproductive functions. The
terminal and vomeronasal nerves also reach the olfactory bulb.
The optic nerve (II cranial nerve)
Special somatic afferent (SSA)
The optic nerve is the nerve of sight. It consists of the ganglion cell axons of the
retina. The optic nerve runs through the optic canal together with the internal
ophthalmic artery. A percentage of the optic fibers cross behind the jugum
sphenoidale, giving rise to the optic chiasm. After the chiasm, the optic fibers
(decussated and non decussated) form the optic tract that reaches the lateral
geniculate body of the thalamus.
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Oculomotor nerve (III cranial nerve)
General somatic efferent (GSE) and general visceral efferent (GVE)
The ocumolotor nerve leaves the brain stem between the cerebral peduncles and
runs rostrally in relation to the cavernous sinus and the trochlear, abducent and
ophthalmic nerves. It exits the cranial cavity through the orbital fissure, forming a
dorsal and a ventral branch.
The dorsal branch innervates the dorsal rectus and levator palpebrae
superioris muscles. The ventral branch innervates the medial rectus, ventral
rectus, and ventral oblique muscles. The GVE component is formed by fibers that
reach the ciliary ganglion. The parasympathetic postganglionic fibers that leave
this ganglion form the short ciliary nerves that run with the optic nerve to
innervate the ciliary and the pupillary sphincter muscles.
Proprioceptive fibers from the extra-ocular muscles travel in the III, IV and
VI cranial nerves and communicate with the ophthalmic nerve at the level of the
cavernous sinus. The soma of these neurons is located in the trigeminal ganglion.
Trochlear nerve (IV cranial nerve)
General somatic efferent (GSE)
The trochlear nerve is the only cranial nerve that leaves the brain stem
dorsolaterally at the level of the rostral medullary velum, where the left and right
nerves decussate (trochlear decussation). It runs, included in the dura mater,
through the lateral portion of the tentorium cerebelli and, then, in the lateral wall
of the cavernous sinus to exit the cranial cavity through the orbital fissure. Outside
of the skull, it is located between the oculomotor nerve and the ophthalmic branch
of the trigeminal nerve. It innervates the dorsal oblique muscle.
Trigeminal nerve (V cranial nerve)
Special visceral efferent (SVE) and general somatic afferent (GSA)
The trigeminal nerve leaves the brain stem at the level of the pons, rostral to the
trapezoid body. It passes through the trigeminal canal (located on the medial
aspect of the petrosal bone) and divides into three nerves: ophthalmic, maxillary
and mandibular. These nerves leave through foramina located in the wing of the
sphenoid bone. The ophthalmic nerve leaves the cranial cavity through the orbital
fissure together with the oculomotor, trochlear and abducent nerves. The
maxillary nerve enters the round foramen, that opens into the alar canal, and exits
through the rostral alar foramen. The mandibular nerve leaves through the oval
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foramen. The three nerves have a sensory component (GSA) but only the
mandibular has a motor component (SVE).
The sensory neurons have their bodies located in the trigeminal ganglion
(also called Gasser's ganglion or semilunar ganglion). This is located in a trigeminal
cavity of the dura mater in the rostral opening of the trigeminal canal in the
rostromedial surface of the petrous temporal bone. There is an exception in the
case of the proprioceptive neurons, whose fibers form the mesencephalic tract of
the trigeminal nerve inside the brain stem. The soma of these neurons is located in
the nucleus of the mesencephalic tract of the trigeminal nerve, situated lateral to
the periaqueductal gray matter of the mesencephalon.
. The ophthalmic nerve
Before going through the orbital fissure, the ophthalmic nerve gives off a sensory
meningeal branch. Just after leaving the cranial cavity, it enters the periorbita and
divides into the following nerves: frontal, lacrimal and nasociliary.
. The frontal nerve is sensory (GSA) to the upper eyelid.
. The lacrimal nerve is sensory to the upper eyelid, conjuntiva and lacrimal
gland. It carries postganglionic parasympathetic fibers from the pterogopalatine
ganglion to the lacrimal gland. These are GVE fibers from the facial nerve.
. The nasociliary nerve gives off the ethmoidal and infratrochlear nerves.
The ethmoidal nerve passes through the ethmoid foramen into the cranial cavity to
reach the cribriform plate and, then, enters the nasal cavity to innervate the nasal
mucosa and the skin of the nasal vestibule. The infratrochlear nerve is located
medial to the orbit. It is sensory to the skin of the medial canthus of the eye (GSA).
The nasociliary nerve sends a branch to the ciliary ganglion that (without
synapsing) forms part of the short ciliary nerves (GVE). The continuation of the
nasociliary nerve forms the long ciliary nerves that are sensory (GSA) to the
eyeball and carry postganglionic sympathetic fibers (from the cranial cervical
ganglion) to the dilator muscle of the pupil and to the smooth muscle fibers of the
periorbita.
. The maxillary nerve
After sending out a meningeal branch, the maxillary nerve leaves the cranial cavity
through the round foramen into the alar canal and, then, through the rostral alar
foramen. It divides into the zygomatic, pterygopalatine and infraorbital nerves.
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. The zygomatic nerve leaves the maxillary nerve at the level of the round
foramen. After exiting through the rostral alar foramen, it enters the periorbita and
divides into the zygomaticotemporal and zygomaticofacial nerves. The
zygomaticotemporal nerve runs over the orbital ligament. It is sensory to the skin
dorsal to the zygomatic arch and the lateral canthus of the eye. It carries
postganglionic parasympathetic fibers from the pterygopalatine ganglion to the
lacrimal gland (these are GVE fibers from the facial nerve). The zygomaticofacial
nerve runs under the orbital ligament. It is sensory to the lower eyelid and lateral
canthus of the eye.
. The pterygopalatine nerve passes over the dorsal surface of the medial
pterygoid muscle. It sends out the caudal nasal nerve and the major, accessory and
minor palatine nerves. These nerves incorporate postganglionic parasympathetic
fibers from the pterygopalatine ganglion (these are GVE and GVA fibers from the
facial nerve) to innervate the nasal and palatine glands. The caudal nasal nerve
enters the nasal cavity through the sphenopalatine foramen. The major palatine
nerve enters the palatine canal through the caudal palatine foramen and
innervates the hard palate. The minor palatine nerve innervates the soft palate,
and the accessory palatine nerve innervates the caudal portion of the hard palate.
. The infraorbital nerve is a continuation of the maxillary nerve. At the level
of the pterygopalatine fossa, the infraorbital nerve sends out the caudal superior
alveolar branches that enter the alveolar foramina of the maxilla (to supply the
caudal upper teeth). Then the infraorbital nerve enters the infraorbital canal via
the maxillary foramen. Within the canal, it sends out the middle superior alveolar
branches which enter the alveolar canals (to supply the middle upper teeth). Just
before leaving the canal, through the infraorbital foramen, the maxillary nerve
sends out the rostral superior alveolar branches through the incisivo-maxillary
canal (to the upper canine and incisor teeth). Once out of the infraorbital canal, the
infraorbital nerve divides into nasal and superior labial branches.
The mandibular nerve
After sending out a meningeal branch, the mandibular nerve exits the cranial
cavity through the oval foramen and divides into the following nerves: masticator,
buccal, lateral pterygoid, medial pterygoid, inferior alveolar, lingual, mylohyoid,
tensor tympani, tensor veli palatine and auriculotemporal.
. The masticator divides into the masseteric and deep temporal nerves to
the masseter and temporal muscles respectively.
. The buccal nerve is sensory for the mucousa of the cheeks. It is also
sensory to the skin located ventrally to the zygomatic arch and dorsocaudally to
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the commissure of the mouth. It incorporates postganglionic parasympathetic
fibers from the otic ganglion to innervate the salivary zygomatic gland (these are
GVE nerve fibers from the glossopharyngeal nerve).
. The lateral and medial pterygoid nerves innervate the lateral and medial
pterygoid muscles respectively.
. The inferior alveolar nerve enters the mandibular canal through the
mandibular foramen to innervate the lower teeth. The rostral, middle and caudal
mental nerves are rostral extensions of the inferior alveolar nerve that exit
through the mental foramina. These nerves are sensory to the lower lip.
. The lingual nerve is sensory for the rostral two thirds of the tongue. The
GSA component is formed by trigeminal fibers. The GVE, GVA and SVA (taste)
components are facial fibers of the chorda tympani that join the lingual nerve in
the dorsomedial surface of the medial pterygoid muscle.
. The mylohyoid nerve is motor to the mylohyoid and rostral belly of the
digastricus muscles. It is also sensory to the skin of the intermandibular region
and, through a communicating branch with the ventral buccal branch of the facial
nerve, to the caudal portion of the lower lip and ventrolateral area of the cheek
(caudal to the region innervated by the mental branches).
. The tensor tympani nerve innervates the tensor tympani muscle. When
this muscle contracts, the manubrium of the malleus moves medially and tightens
the tympanic membrane.
. The tensor veli palatini nerve innervates the tensor veli palatini muscle.
When this muscle acts in combination with the levator veli palatini (innervated by
the glossopharyngeal and vagus nerves), it opens the orifice of the auditory tube
into the pharynx.
. The auriculotemporal nerve leaves the mandibular nerve at the level of the
oval foramen and runs caudally to the retroarticular process of the temporal bone.
It sends out the external acoustic meatus nerve and a branch to the tympanic
membrane. They are sensory to the external acoustic meatus and to the tympanic
membrane respectively. The auriculotemporal nerve receives postganglionic
parasympathetic fibers from the otic ganglion to innervate the salivary parotid
gland (these are GVE fibers from the glossopharyngeal nerve). The rostral
auricular nerves of the auriculotemporal nerve are sensory to the skin of the ear
and the skin that covers the surface of the temporal muscle and the zygomatic
arch. The transverse facial branch is formed by auriculotemporal nerve fibers that
are sensory to the skin located laterally and ventrally to the zygomatic arch. A
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communicating ramus between the auriculotemporal nerve and the dorsal buccal
branch runs dorsal to the masseter muscle. It is sensory to the skin of the cheek,
ventral to the zygomatic arch.
Abducent nerve (VI cranial nerve)
General somatic efferent (GSE)
The abducent nerve leaves the brain stem at the level of the trapezoid body, lateral
to the pyramids. It runs rostrally to leave the cranial cavity through the orbital
fissure. It innervates the retractor bulbi and lateral rectus muscles.
Facial nerve (VII cranial nerve)
Special visceral efferent (SVE), general visceral efferent (GVE), general visceral
afferent (GVA), special visceral afferent (SVA) and general somatic afferent (GSA)
The soma of the neurons of the SVE component of the facial nerve form the motor
nucleus of the facial nerve. This is located ventrolaterally in the medulla oblongata,
rostral to the nucleus ambiguus. The axons ascend dorsomedially to form a loop
(named internal genu of the facial nerve) around the abducent nucleus and they
descend, ventrally to the nucleus of the spinal tract of the trigeminal nerve, to leave
the brain stem forming the facial motor root. The facial fibers for the GSA, GVE,
GVA and SVA components form the intermediate nerve.
The motor and intermediate nerve fibers of the facial nerve leave the brain
stem ventrolaterally at the rostral portion of the trapezoid body. They are
surrounded by a common sheath of dura mater together with the
vestibulocochlear nerve. After a short distance, they enter the facial canal (located
in the petrosal part of the temporal bone) through the internal acoustic meatus.
Inside the facial canal, the nerve turns caudally and laterally, forming the external
genu of the facial nerve. At this point the geniculate ganglion is located. This
ganglion contains the bodies of the afferent neurons.
The major petrosal nerve (GVE and GVA) leaves the facial nerve at the level
of the geniculate ganglion. It is joined by sympathetic postganglionic fibers from
the cranial cervical ganglion via the internal carotid plexus. These sympathetic
fibers form the deep petrosal nerve. Both nerves (the major and the deep)
constitute the nerve of the pterygoid canal, which leaves the skull through a small
foramen on the rim of the rostral alar foramen. This nerve reaches the
pterogopalatine ganglion where the parasympathetic neurons synapse on
postganglionic neurons that innervate the lacrimal gland by means of the lacrimal
nerve (a branch of the ophthalmic nerve) and the zygomaticotemporal nerve (a
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branch of the maxillary nerve). Other postganglionic fibers are incorporated to the
pterygopalatine nerve (also a branch of the maxillary nerve) to innervate the
palate and nasal glands.
The facial nerve continues along the facial canal and gives off the stapedial
nerve (SVE) to innervate the stapedius muscle. This muscle modifies the position
of the stapes in the vestibular window.
The next branch to leave the facial nerve within the facial canal is the
chorda tympani (GVE, GVA and SVA). This nerve passes through the canaliculus of
the chorda tympani to reach the middle ear cavity. It runs medial to the tympanic
membrane and exits the skull through the petrotympanic fissure to join the lingual
nerve (a branch of the mandibular nerve). The efferent fibers (GVE) are
parasympathetic preganglionic neurons that reach the mandibular and sublingual
ganglia in order to innervate the mandibular and sublingual salivary glands
respectively. The afferent fibers transmit sensations from the rostral two thirds of
the tongue including taste (SVA). The soma of the GVA and SVA neurons is located
at the geniculate ganglion of the facial nerve (inside the facial canal).
The facial nerve is joined by the auricular branch of the vagus nerve. This
leaves the vagus nerve at the level of the jugular foramen and constitute the lateral
internal auricular nerve (a branch of the facial nerve) that innervates the external
ear canal.
Once the facial nerve has become external through the stylomastoid
foramen, it gets thicker because the epineurium increases. As the facial nerve runs
rostrally, it gives rise to the following nerves: the caudal auricular nerve (SVE for
the platysma and caudal auricular muscles), the caudal and middle internal
auricular nerve (GSA fibers for the auricular concha), the lateral internal auricular
nerve (formed by GSA vagal fibers to the external ear canal), the digastric branch
(SVE for the caudal belly of the digastricus muscle) and the stylohyoid branch (SVE
for the stylohyoid and jugulohyoid muscles).
When the facial nerve passes the caudal border of the mandible on the
surface of the masseter muscle, it sends out the following SVE branches: cervical,
buccal and auriculopalpebral. The cervical branches innervate the
parotidoauricularis and the sphincter colli muscles before joining the ventral
branch of the second cervical spinal nerve. The buccal nerve divides into dorsal
and ventral branches. These innervate the buccinator, the orbicularis oris and the
nasolabial muscles. The dorsal and ventral buccal branches receive GSA fibers
through communicating branches of the auriculotemporal nerve and mylohyoid
nerves respectively (these nerves are branches of the mandibular nerve). The
auriculopalpebral nerve divides into palpebral and rostral auricular nerves. The
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palpebral nerve forms a plexus that innervates the rostral auricular, nasolabial and
palpebral muscles. The rostral auricular branch innervates the scutuloauricularis
muscles.
There is no evidence for proprioceptive afferents in the facial nerve that
innervates the superficial muscles of the face, most likely the trigeminal nerve
contains afferents from intramuscular and cutaneous receptors involved in mimic
movements.
Vestibulocochlear nerve (VII cranial nerve)
Special somatic afferent (SSA)
The vestibulocochlear nerve consists of fibers that transmit stimuli from receptors
located in the inner ear.
The vestibulocochlear nerve enters the cranial cavity through the internal
acoustic meatus (located in the medial surface of the petrosal part of the temporal
bone) and enters the brain stem at the level of the trapezoid body. The fibers of the
vestibular root (sense of balance) end in the vestibular nuclei and the fibers of the
cochlear root (sense of hearing) reach the cochlear nuclei. Same cochlear fibers are
efferent to the organ of Corti.
Glossopharyngeal nerve (IX cranial nerve)
Special visceral efferent (SVE), general visceral efferent (GVE), general visceral
afferent (GVA) and special visceral afferent (SVA)
The glossopharyngeal nerve leaves the brain stem at the level of the medulla
oblongata, caudally to the trapezoid body.
The parasympathetic preganglionic fibers of the glossopharyngeal nerve
form the tympanic nerve (GVE). This nerve enters the middle ear to form the
tympanic plexus. Fibers from this plexus form the minor petrosal nerve that leaves
the skull through a small foramen (located dorsocaudally to the oval foramen) to
reach the otic ganglion. The parasympathetic postganglionic fibers join the
auriculotemporal and the buccal nerves (both are branches of the mandibular
nerve) to innervate the parotid and zygomatic salivary glands respectively.
The remaining fibers of the glossopharyngeal nerve exit the cranial cavity
through the jugular foramen and, then, through the tympano-occipital fissure,
along with the vagus and accessory nerves. The glossopharyngeal nerve sends a
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sensory branch (GVA) to the carotid sinus and carotid body. Subsequently, it
divides into lingual and pharyngeal branches.
The lingual branch (GVE, GVA and SVA) innervates the tonsils and the root
of the tongue. The pharyngeal branch and the vagus nerve form the pharyngeal
plexus, which innervates the muscles and mucosa of the pharynx. This plexus is
composed of motor fibers (SVE and GVE) and sensory fibers (GVA), and is joined
by sympathetic postganglionic fibers from the cranial cervical ganglion.
In the dog, the soma of the sensory neurons is located in a ganglion at the
level of the jugular foramen.
Vagus nerve (X cranial nerve)
Special visceral efferent (SVE), general visceral efferent (GVE), general visceral
afferent (GVA), special visceral afferent (SVA) and general somatic afferent (GSA)
The vagus nerve leaves the brain stem at the level of the medulla oblongata, caudal
to the glossopharyngeal nerve.
Most of the vagal fibers are visceral sensory (GVA). The rest are made up of
visceral motor (GVE), special visceral motor (SVE), sensory to the taste buds of the
epiglottis (SVA) and somatic sensory (GSA) to the ear canal.
The vagus nerve leaves the cranial cavity through the jugular foramen and,
then, through the tympano-occipital fissure. At the level of the jugular foramen it
sends a sensory auricular branch (GSA) to join the facial nerve in order to reach
the skin of the ear canal through the lateral internal auricular nerve.
The proximal vagal ganglion (also named jugular ganglion) is located at the
level of the jugular foramen. It is formed by the soma of the somatic afferent
neurons (GSA). The soma of the GVA and SVA neurons is located at the distal vagal
ganglion (also named nodose ganglion). This is situated outside the tympano-
occipital fissure and topographically related with the glossopharyngeal, accessory
and hypoglossal nerves, and the cranial cervical ganglion.
The pharyngeal ramus (SVE, GVE and GVA) leaves the vagus nerve at the
level of the distal vagal ganglion. It is joined by fibers from the glossopharyngeal
ramus and sympathetic postganglionic fibers (from the cranial cervical ganglion)
to form the pharyngeal plexus. This innervates the pharyngeal muscles and the
cranial part of the esophagus.
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The cranial laryngeal nerve branches off from the vagus nerve also at the
level of the distal vagal ganglion. It divides into an external ramus and an internal
ramus. The external ramus (SVE) innervates the cricothyroideus muscle. The
internal ramus (GVE and GVA) innervates the mucosa of the larynx, rostral to the
vocal folds, and the taste buds of the epiglottis (SVA).
The vagus nerve descends into the thoracic cavity together with ascending
sympathetic fibers, forming the vagosympathetic trunk. At the level of the middle
cervical ganglion, the vagus nerve leaves the sympathetic fibers and sends out
cardiac branches formed by parasympathetic preganglionic fibers (GVE) and
sensory fibers (GVA). On the left side, the nerve forms the left recurrent laryngeal
nerve that passes around the aortic arch. On the right side, the right recurrent
laryngeal nerve turns around the right subclavian artery. Both recurrent laryngeal
nerves run cranially becoming the left and the right caudal laryngeal nerves. They
innervate the trachea (GVE and GVA), the esophagus (SVE, GVE and GVA), and the
laryngeal muscles (SVE), except for the cricothyroid muscle that is innervated by
the external ramus of the cranial laryngeal nerve. The laryngeal nerves also
innervate the mucosa of the larynx caudal to the vocal folds (GVE and GVA).
At the middle mediastinum, the vagus nerve sends branches to the bronchi,
esophagus and heart. Just caudal to the bronchi, each left and right vagus nerves
form a dorsal and a ventral branch. The dorsal branches (left and right) unite, as do
the ventral ones, to form the dorsal and ventral vagal trunks respectively. In the
abdominal cavity, the dorsal vagal trunk joins the celiacomesenteric plexus so the
fibers may follow the vessels to reach the viscera. The ventral vagal trunk
innervates the lesser curvature of the stomach and the liver. These fibers are made
of preganglionic parasympathetic (GVE) and visceral sensory (GVA) neurons.
Although the pharyngeal and laryngeal muscles were considered lacking of
spindles, spindle-like receptors to stretch have been found indicating the
possibility of GSA fibers for proprioception in the glossopharyngeal and vagus
nerves.
Accessory nerve (XI cranial nerve)
General somatic efferent (GSE) and special visceral efferent (SVE)
The accessory nerve consists of cranial and spinal roots. The neurons that form the
cranial roots have their bodies in the nucleus ambiguus in the medulla oblongata.
The neurons of the spinal roots have their bodies in the motor nucleus of the
accessory nerve, located in the dorsolateral portion of the ventral horn of the
cervical spinal cord segments (from C1 to C7).
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The spinal roots leave the spinal cord between the dorsal and ventral roots
of the cervical spinal nerves, and lie dorsal to the denticulate ligament (under the
dorsal spinal roots). They run rostrally to enter the cranial cavity, through the
foramen magnum, and join the cranial roots. These leave the medulla oblongata
vetrolaterally. Cranial and spinal accessory nerve roots unite to become the
external branch of the accessory nerve (GSE). Some fibers from the cranial roots
join the vagus nerve to form the internal branch of the accessory nerve. This
branch becomes part of the recurrent laryngeal nerve (SVE).
Upon exiting the cranial cavity through the jugular foramen and, then,
through the tympano-occipital fissure, the external branch of the accessory nerve
descends to innervate the trapezius, omotransversarius, sternocephalicus and
cleidocephalicus muscles. The latter two muscles are also innervated by ventral
branches of the cervical spinal nerves.
As there are communications between the accessory nerve and the cervical
spinal nerves, it has been proposed that the soma of sensory cells (GSA) for
proprioception may be located in the dorsal root ganglia.
Hypoglossal nerve (XII cranial nerve)
General Somatic efferent (GSE)
The hypoglossal nerve is motor to muscles of the tongue (intrinsic and extrinsic)
and genihyoideus and thyrohyoideus muscles. It leaves the medulla oblongata
laterally to the pyramids by means of several rootlets. The nerve exits the skull
through the hypoglossal canal and goes ventrorostrally, lateral to the external
carotid artery, to run parallel to the lingual artery. In its course, the hypoglossal
nerve communicates with the ventral branch of the first cervical spinal nerve
forming, the cervical loop (ansa cervicalis).
Although the hypoglossal nerve is considered a motor nerve, there are
afferents that respond to stretch. As this nerve has no sensory ganglion, it has been
proposed that the soma of the afferent neurons may be located at the dorsal root
ganglion of C1 (the connection will be through the ansa cervicalis).
Bibliography
Adatia A.K. and Gehring, E. N. Proprioceptive innervation of the tongue. J. Anat., 110 (2): 215-220
(1971).
Afifi, A. K. and Bergman, R. A. Functional neuroanatomy. McGraw-Hill. (1998).
Agüera, E, Vivo, J. Neuroanatomía veterinaria. Sistema nervioso central. IM, Córdoba. (1989).
13
Aige-Gil, V. El encéfalo de perro. Atlas fotográfico. Manuals de la Universitat Autònoma de
Barcelona. Veterinària. Universidad Autónoma de Barcelona (2002).
Aige-Gil, V. Functional neuroanatomy of the dog. ISBN 978-84-490-2896-0. Col.lecció Materials.
Col.lecció Materials 226. Universidad Autónoma de Barcelona (2012).
Asseheuer, J., Sager, M. MRI and CT atlas of the dog. Blackwell Science (1997).
Atasever, A., Çelik, H. H., Durgun, B. and Ytlmaz, E. The course of the proprioceptive afferents from
extrinsic eye muscles. Turkish Neurosurgery 2: 183· 186 (1992).
Bartolami, R. Veggeti, Callegari, E., Lucchi, ML., and Palmieri, G. Afferent fibers and sensory ganglion
cells within the oculomotor nerve in some mammals and man. I. Anatomical investigations.
Arch. Ital. Biol. 115(4): 355-385 (1977).
Baumel, J.J. Trigeminal-facial nerve communications. Their function in the facial muscle innervation
and reinnervation. Arch. Otolaryngol. 99 (1): 34-44 (1974).
Bernardini, M. Neurologia del cane e del gatto. Poletto Editore (2002).
Bianconi, R. and Molinari, G. Electrographic evidence of muscle spindles and other sensory endings
in intrinsic laryngeal muscles of the cat. Acta Oto-laryngologica, 55 (1-6): 253-259 (1962).
Blanconi, B., Molinary, G. Electroneurographic evidence of muscle spindles and other sensory
endings in the intrinsic laryngeal mucles of he cat. Acta Oto-laryng., 55: 253-259 (1962).
Boroffka, S. A. E. B., Görig, C. Auriemma, E., Passon-Vatenburg, M. H. A. C., Voorhout, G., and Barthez,
P. Magnetic resonance imaging of the canine nerve. Veterinary Radiology & Ultrasound, Vol. 49,
No. 6, pp 540-544 (2008).
Bortolami, R., Veggetti, A., Callegari, E., Lucchi, M.L. and Palmieri, G.. Afferent fibers and sensory
ganglion cells within the oculomotor nerve in some mammals and man. I. Anatomical
investigations.. Arch. Ital. Biol. 115 (4): 355-385. (1977).
Boyd,J.S. A colour atlas of clinical anatomy of the dog and cat. Wolfe Publishing Ltd. (1991).
Brancatisano, A., Davis, P. Van Der Touw, T. and Wheatley, J. R. Effect of upper airway negative
pressure on proprioceptive afferents from the tongue. TRhe American Physiological Society
(1999).
Budras, K., Mc Carthy, P. H., Fricke, W. and Richter, R. Anatomy of the dog. Chlütersche. (5th ed)
(2007).
Clifford R Weir, Paul C Knox, Gordon N Dutton, Does extraocular muscle proprioception influence
oculomotor control. Br J Ophthalmol, 84:1071–1074 (2000).
Climent, S., Sarasa, M. Muniesa, P. and Terrado, J. Manual de anatomía y embriología de los animales
domésticos. Conceptos básicos y datos aplicativos. Sistema nervioso central y órganos de los
sentidos. Acribia (1998).
Cooper, S., Daniel, P. M. and Whitteridge, D. Afferent impulses in the oculomotor nerve,from the
extrinsic eye muscles. J. Physiol. II3, 463-474 (I95I).
Cooper, S., Daniel, P.M. and Whitteridge, D. Afferent impulses in the oculomotor nerve from the
extrinsic eye muscles. J. Physiol., 113: 463-474 (1951).
Crossman, A. R. and Neary, D. Neuroanatomy. Churchill Livingstone. (2ª ed.) 2000.
De Lahunta, A. and Glass, E. Veterinary neuroanatomy and clinical neurology. Saunders Elsevier.
(3ª ed.) (2009).
Dewey, C. W. A practical guide to canine and feline neurology. Iowa State Press (2003).
Dyce, K.M., Sack, W. O. and Wensing, C. J. G. Textbook of veterinary anatomy. W. B. Saunders
Company (1987).
E. Manni, E., Bortolani, R. and Desole, C. Eye muscle proprioception and the semilunar ganglion. Exp.
Neurol., 16 (2):226-236 (1966).
Evans, H. E. Miller’s anatomy of the dog. Elsevier Saunders (4ª ed.) (2013).
Fuchis, A.F. and Kornhuber, H.H. Extraocular muscle afferents to the cerebellum of the cat. J.
Physiol., 200:713-722 (1969).
Gentle, a. and Ruskell, G. Pathway of primary afferent nerve fibers serving proprioception in
monkey extraocular muscles. Ophthalmic and physiological optics. 17(3):225-231 (1997).
14
Gentle, A., Ruskell and G. Pathway of the primary afferent nerve fibers serving proprioception in
monkey extraocular muscles. Ophthalmic and Physiological Optics. 17 (3): 225-231 (1997).
Gomes, E., Degueurce, C. Ruel, Y., Dennis, R. and Begon, D. Anatomic study of cranial nerve
emergence and associated skull foramina in cats using CT and MRI. Veterinary Radiology &
Ultrasound, Vol. 50, No. 4, pp 398-403 (2009).
Hwang, J., John, W. M. and Bartlett, D. Jr. Afferent pathways for hypoglossal and phrenic responses
to changes in upper airway pressure. Respir. Physiol. 55: 341–354 (1984).
Jaggy, A. Small animal neurology. Schlütersche (2010).
Jenkins, T. W. Functional mammalian neuroanatomy. Lea & Febiger. Philadelphia (1972).
King, A. S. Physiological and clinical anatomy of the domestic animals. Vol. 1. Central nervous
system. Oxford Science Publications (1994).
King, A. S. The cardiorespiratory system. Blackwell Science (1999).
Kuehn, D.P., Templeton P.J. and Maynard, J.A. Muscle spindles in the velopharyngeal musculature of
humans. J. Speech Hear Res. 33(3): 488-493 (1990).
Kumar, M.S.A. Clinically oriented anatomy of the dog and cat. Linus Learning. 2013
Lorenz, M. D., Coates, J. R. and Kent, M. Handbook of veterinary neurology. Elsevier Saunders. (5th
ed.) (2011).
Lorenzo Fernández, V. and Bernardini, M. Neurología del perro y del gato. Intermédica (2007).
Lucas Keene, M.F.. Muscle spindles in human laryngeal muscles. Journal of Anatomy, 95 (1):25-29
(1970).
Manni, E. Bortolami, R. Pettorossi, V.E. and Callegari, E. Trigeminal afferent fibers in the trunk of the
oculomotor nerve of lambs. Experimental Neurology. 50 (2): 465-476 (1976).
Manni, E., Bortolami, R., Petorossi, V.E. and Callegari, E. Trigeminal afferent fibers in the trunk of the
oculomotor nerve of lambs. Exp. Neurology, 50 (2): 465-476 (1976).
Manni, E., Bortolani, R. and Deriu, P.L. Superior muscle proprioception and the trochlear nerve. Exp.
Neurol. (26 (3): 543-550 (1970).
Manni, E., Bortolani, R. and Desole, C. Peripheral pathway of eye muscle proprioception. Exp.
Neurol., 22 (1): 1-12. (1961).
Manni, E., Palmieri, G. and Marini, R. Peripheral pathway of the proprioceptive afferents from the
lateral rectus muscle of the eye. Exp. Neurology:30 (1): 46-53 (1971).
Manni, E., Palmieri, G. and Marini, R. Peripheral pathway of the proprioceptive afferents from the
lateral rectus muscle of the eye. Experimental Neurology. 30 (1): 46-53 (1971).
Manni. E., Bortolami, R. and Desole, C. Peripheral pathway of eye muscle proprioception.
Experimental Neurology. 22 (1): 1-12 (1968).
Manni. E., Bortolami, R. and Desole, C. Superior oblique muscle proprioception and the trochlear
nerve. Experimental Neurology. 26 (3): 543-550 (1970).
Manni. E., Bortolami, R. and Desole, C. The muscle proprioception and the semilunar ganglion.
Experimental Neurology. 16 (2): 226-236 (1966).
Martin, J.H. Neuroanatomy. Appleton & Lange (1996). Mesencephalic trigeminal nucleus in
macaque monkeys. Anat. Rec. 291(8): 974–987 (2008).
Mora, F. and Sanguinetti, A. M. Diccionario de neurociencia. Alianza Editorial. 2004.
Murray, J.G. Innervation of the intrinsic muscles of the cat's larynx by the recurrent laryngeal nerve:
a unimodal nerve. J. Physiol., 135: 206-212 (1957).
Noden, D. M. and De Lahuunta, A. The embriology of domestic animals. Development mechanisms
and malformations. Williams & Wilkins (1985).
Orts Llorca, F. Anatomía Humana. Tomo II. Sistema nervioso central y órganos de los sentidos.
Sistema neurovegetativo. Ed. Científico-médica. (4ª ed.) (1972).
Parry, A. T. and Volk, H. A. Imaging the cranial nerves. Veterinary radiology & Ultrasound, Vol. 52,
No. 1, Supp. 1, pp S32-S41 (2011).
Porter, J. and Guthrie. Innervation of monkey extraocular muscles: Localization of sensory and
motor neurons by retrograde transport of horseradish peroxidase. J. of Comparative Neurology.
218(2): 208-219 (1983).
15
Porter, J.D. and Spencer, R.F. Localization and morphology of cat extraocular muscle afferent
neurons identified by retrograde transport of horseradish peroxidase. Journal of Comparative
Neurology, 204 (1): 56-64 (1982).
Porter, J.D. and Spencer, R.F. Localization and morphology of cat extraocular muscle afferent
neurons identified by retrograde transport of horseradish peroxidase. J. of Comparative
Neurology 204(1):56-64 (1982).
Porter, J.D., Guthrie, B.L. and Sparks, D.L. Innervation of monkey extraocular muscles: Localization
of sensory and motor neurons by retrograde transport of horseradish peroxidase. Journal of
Comparative Neurology: 218(2): 208-219 (1983).
Rossi, G. and Cortesina, G. Morphological study of the laryngeal muscles in man: insertions and
courses of the muscle fibers, motor end plates and proprioception. Acta Oto-laryngologica, 59
(2-6): 575-592 (1965).
Ruberte, J, Sautet, J., Navarro, M., Carretero, A. and Pons, J. Atlas de anatomía del perro y del gato.
Vol 1. Cabeza y cuello. Multimédica (1995).
Schaller, O. Nomina Anatomica Veterinaria. Fifth edition. Ferdinand Enke Verlag. Sttugart (2005).
Snell, R.S. Clinical neuroanatomy for medical students. Lippincott Williams & Wilkins. (5ª ed.)
(2001).
Thomson, C. and Hahn, C. Veterinary Neuroanatomy. A clinical approach. Saunders Elsevier (2012).
Vega, J.A., Carlos, F. de, García-Suárez, O., Calavia, M.G., Alvarez-Suárez, A.
López-Muñiz and A. Cobo, J. Sensory innervation of the human constrictor pharyngeal muscles.
XXV Congreso de Sociedad Anatómica Española, Madrid (2011).
Wang, N. and May, P.J., Peripheral muscle targets and central projections of the
Weir, C.R, Knox, P.C. and Dutton, G,N. Does extraocular muscle proprioception influence oculomotor
control? Br J Ophthalmol .84:1071–1074 (2000).
Zhang J, Yang R, Pendlebery W, Luo P. Monosynaptic circuitry of trigeminal proprioceptive afferents
coordinating jaw movement with visceral and laryngeal activities in rats. Neuroscience.
135(2):497-505 (2005).