cranial nerves...introduction the first and shortest cranial nerve. it is the nerve to transmits...
TRANSCRIPT
CRANIAL NERVES
Khaleel Alyahya, PhD, MEdwww.khaleelalyahya.net
RESOURCES
Essential of Human
Anatomy & Physiology
By Elaine Marieb and Suzanne Keller
Human Brain
By John Nolte
Clinical
Anatomy
By Richard Snell
Atlas of Human AnatomyBy Frank Netter
Gray’s Anatomy
By Richard Drake, Wayne
Vogl & Adam Mitchell
KENHUB
www.kenhub.com
INTRODUCTION
There are 12 pairs of cranial nerves in our body (I-XII)
They are called cranial nerve because they originateddirectly from the brain.
They communicate and relay information between the brainand parts of the body, primarily to and from regions of thehead and neck.
They are generally named from anterior to posterior basedon structure or function.
• For example, the olfactory nerve (I) provides smell, and the facial nerve(VII) provides motor innervation to the face.
By Khaleel Alyahya, PhD, MEd 3
OLFACTORY SENSORY
INTRODUCTION
The first and shortest cranial nerve.
It is the nerve to transmits special sensory information tohave a sense of smell.
It is one of two nerves that do not emerge from brainstem,
Elderly people usually have less sensation of smellprobably because of progressive reduction in number ofolfactory cells.
By Khaleel Alyahya, PhD, MEd 5
ORIGIN & EXIT
It passes through the cribriform plate of the ethmoid boneand attached to olfactory bulb.
The fibers enter the olfactory bulb, which lies in theolfactory groove, within the anterior cranial fossa.
The olfactory tract runs inferiorly to the frontal lobe.
Function is to carry afferent impulses for the sense ofsmell.
By Khaleel Alyahya, PhD, MEd 6
OPTIC SENSORY
INTRODUCTION
It is the second cranial nerve.
It is responsible for transmitting the special sensoryinformation for sight.
It is one of two nerves that do not emerge from brainstem.
It has a unique anatomical relation to the brain and issurrounded by cranial meninges (like olfactory nerve).
By Khaleel Alyahya, PhD, MEd 8
ORIGIN & EXIT
Optic nerve arises from the ganglion cells of the retina andpass through the optic foramen (optic canal).
At the hypothalamus, the two nerves cross forming theoptic chiasma.
They continue to the thalamus where they synapse.
From there, the optic radiation fibers run to the visualcortex.
Function is to by carry afferent impulses for vision
By Khaleel Alyahya, PhD, MEd 9
OCULOMOTOR MOTOR
INTRODUCTION
It is the third cranial nerve.
It offers motor and parasympathetic innervation to many ofthe ocular structures.
Motor to the muscles that move the eye except thesuperior oblique and the lateral rectus.
Parasympathetic supplies the sphincter pupillae and theciliary muscles of the eye.
By Khaleel Alyahya, PhD, MEd 11
ORIGIN & EXIT
Fibers extend from the anterior aspect of midbrain (sulcus
on walls of interpeduncular fossa), pass through the
superior orbital fissure, and go to the extrinsic eye
muscles.
Functions in raising the eyelid, directing the eyeball,
constricting the iris, and controlling lens shape.
Damage to Oculomotor nerve may result in lazy eye
(drooping of the eyelid).
By Khaleel Alyahya, PhD, MEd 12
TROCHLEAR MOTOR
INTRODUCTION
It is the fourth paired cranial nerve.
It is the smallest cranial nerve (by number of axons).
It is the only cranial nerve to emerge from the dorsal sideof the brain, and also has the longest pathway.
It has a purely somatic motor function.
By Khaleel Alyahya, PhD, MEd 14
ORIGIN & EXIT
Motor to the superior oblique muscle of the eyeball.
Fibers emerge from the posterior aspect of midbrain
(superior medullary velum) and enter the orbits via the
superior orbital fissures to innervate the superior oblique
muscle.
Injury to this nerve will result in loss of function of the
superior oblique muscle, limiting the ability to looking down
and outward (inferolateral ocular movement).
By Khaleel Alyahya, PhD, MEd 15
TRIGEMINAL MIXED
INTRODUCTION
It is the fifth paired cranial nerve.
It is also the largest cranial nerve.
Sensory: The three terminal branches of trigeminalinnervate the skin, mucous membranes and sinuses of theface.
Motor: Only the mandibular branch of trigeminal has motorfibers and it innervates the muscles of mastication:
By Khaleel Alyahya, PhD, MEd 17
ORIGIN & EXIT
Composed of three sensory divisions.
• Ophthalmic V1
o This branch passes through the superior orbital fissure.
o Sensory from superior part of face.
• Maxillary V2
o Sensory passes through the foramen rotundum.
o It supplies the bottom of the nose, skin over the maxilla, the
upper teeth and gums.
• Mandibular V3
o Mixed passes through the foramen ovale.
o It supplies the skin over the mandible and the lower teeth and
gums.
By Khaleel Alyahya, PhD, MEd 18
ABDUCENS MOTOR
INTRODUCTION
It is the sixth paired cranial nerve.
It has a purely somatic motor function.
It arises from the abducens nucleus in the pons of thebrain and exits the brainstem at the junction of the ponsand the medulla.
It innervates a single muscle named the lateral rectus,one of the muscles of oculomotion.
By Khaleel Alyahya, PhD, MEd 20
ORIGIN & EXIT
Motor to the lateral rectus muscle of the eyeball which
allows the eye to adduct.
Fibers leave the inferior pons (Sulcus between pons &
medulla on anterior surface) and enter the orbit via the
superior orbital fissure.
Injury to this nerve will result in difficulty in rotating the
eyeball outward and will produce diplopia (double vision).
By Khaleel Alyahya, PhD, MEd 21
FACIAL MIXED
INTRODUCTION
It is the seventh paired cranial nerve.
The course of the facial nerve is very complex.
There are many branches, which transmit a combinationof sensory, motor and parasympathetic fibers.
Anatomically, the course of the facial nerve can be dividedinto two parts:
• Intracranial – the course of the nerve through the cranialcavity, and the cranium itself.
• Extracranial – the course of the nerve outside the cranium,through the face and neck.
By Khaleel Alyahya, PhD, MEd 23
ORIGIN & EXIT
It emerges from the cerebellopontine angle by two roots:
• Medial motor root contains motor fibers.
• Lateral root (nervous intermedius) contains parasympathetic & tastefibers.
Passes through internal auditory meatus to inner ear where itruns in facial canal.
Emerges from the stylomastoid foramen and enters the parotidgland where it ends.
Motor functions include;
• Facial expression.
• Transmittal of parasympathetic impulses to lacrimal and salivary glands(submandibular and sublingual glands).
Sensory function is taste from taste buds of anterior 2/3 of thetongue.
By Khaleel Alyahya, PhD, MEd 24
BELL’S PALSY
The most common condition of facial nerve injury.
Paralysis results from infection and inflammation of thenerve as it passes through the facial canal.
The resulting pressure on the nerve causes the paralysisof the facial muscles.
Paralysis of facial muscles on affected side and loss oftaste sensation.
Lower eyelid and corner of mouth droop.
Tears drip continuously and eye cannot be completelyclosed
Condition may disappear spontaneously without treatment.
By Khaleel Alyahya, PhD, MEd 25
VESTIBULOCOCHLEARSENSORY
INTRODUCTION
It is the eighth paired cranial nerve.
It is comprised of two parts; vestibular fibersand cochlear fibers.
Both have a purely sensory function.
The vestibular and cochlear portions of thevestibulocochlear nerve are functionally discrete, and sooriginate from different nuclei in the brain:
• Vestibular Component – arises from the vestibular nucleicomplex in the pons and medulla.
• Cochlear Component – arises from the ventral and dorsalcochlear nuclei, situated in the inferior cerebellar peduncle.
By Khaleel Alyahya, PhD, MEd 27
ORIGIN & EXIT
Fibers arise from the hearing and equilibrium apparatus of theinner ear, pass through the internal auditory meatus (internalacoustic meatus), and enter the brainstem at the pons-medullaborder.
Has two divisions:
• Cochlear nerve for hearing.
• Vestibular nerve for equilibrium.
Function is to carry sensory; equilibrium and hearing
Lesions, mostly tumors, on or near this cranial nerve may result in:
• tinnitus (ringing or buzzing in the ears)
• impairment or loss of hearing
• loss of balance (vertigo)
By Khaleel Alyahya, PhD, MEd 28
GLOSSOPHARYNGEAL MIXED
INTRODUCTION
It is the ninth paired cranial nerve.
It has a mixed sensory and parasympathetic composition.
Sensory: innervates the followings:
• oropharynx
• carotid body and sinus
• posterior 1/3 of the tongue
• middle ear cavity
• eustachian tube
Special Sensory: provides taste sensation to the posterior 1/3 ofthe tongue.
Motor: innervates the stylopharyngeus muscle of the pharynx.
Parasympathetic: provides parasympathetic innervation to theparotid gland.
By Khaleel Alyahya, PhD, MEd 30
ORIGIN & EXIT
It originates in the medulla oblongata of the brain.
It emerges from the anterior aspect of the medulla, movinglaterally in the posterior cranial fossa.
The nerve leaves the cranium via the jugular foramen.
At this point, the tympanic nerve arises.
Immediately outside the jugular foramen lie two ganglia(collections of nerve cell bodies).
They are known as the superior and inferior ganglia – theycontain the cell bodies of the sensory fibers in theglossopharyngeal nerve.
By Khaleel Alyahya, PhD, MEd 31
ORIGIN & EXIT
The glossopharyngeal nerve descends to the neck, anterolateral tothe internal carotid artery.
At the inferior margin of the stylopharyngeus muscle, severalbranches arise to provide motor innervation to the muscle.
The nerve enters the pharynx by passing between the superiorand middle pharyngeal constrictors.
Also, it gives rise to the carotid sinus nerve, which providessensation to the carotid sinus and body.
Within the pharynx, it terminates by dividing into several branches:
• Lingual
• Tonsil
• Pharyngeal
By Khaleel Alyahya, PhD, MEd 32
VAGUS MIXED
INTRODUCTION
It is the tenth cranial nerve.
It is the only cranial nerve that extends beyond the head andneck to reach the abdomen.
It is a functionally diverse nerve, offering many differentmodalities of innervation.
Due to its widespread functions, pathology of the vagus nerveis implicated in a vast variety of clinical cases.
By Khaleel Alyahya, PhD, MEd 34
ORIGIN & EXIT
It originates from the medulla of the brainstem.
It exits the cranium via the jugular foramen, with the glossopharyngeal and
accessory nerves, respectively.
Within the cranium, the auricular branch arises to supplies sensation to the
posterior part of the external auditory and canal external ear.
It passes into the carotid sheath, travelling inferiorly with the internal jugular vein
and common carotid artery.
At the base of the neck, the right and left nerves have different pathways:
• The right vagus nerve passes anterior to the subclavian artery and posterior to the
sternoclavicular joint, entering the thorax.
• The left vagus nerve passes inferiorly between the left common carotid and left
subclavian arteries, posterior to the sternoclavicular joint, entering the thorax.
By Khaleel Alyahya, PhD, MEd 35
ACCESSORY MOTOR
INTRODUCTION
It is the eleventh paired cranial nerve.
It has a purely somatic motor function, innervating thesternocleidomastoid and trapezius muscles.
It is divided into two parts:
• Spinal part
• Cranial part
By Khaleel Alyahya, PhD, MEd 37
ORIGIN & EXIT
The spinal portion arises from neurons of the upper spinal cord,specifically C1-C5/C6 spinal nerve roots.
These fibers unite to form the spinal part of the accessory nerve,which then runs superiorly to enter the cranial cavityvia the foramen magnum.
The nerve travel to the posterior cranial fossa to reach the jugularforamen.
It briefly meets the cranial portion of the accessory nerve, beforeexiting the skull (along with the glossopharyngeal and vagusnerves).
Outside the cranium, the spinal part descends along the internalcarotid artery to reach and innervate the sternocleidomastoidmuscle.
It then moves across the posterior triangle of the neck to supplymotor fibers to the trapezius.
By Khaleel Alyahya, PhD, MEd 38
ORIGIN & EXIT
The cranial portion is much smaller and arises from the lateralaspect of the medulla oblongata.
It leaves the cranium via the jugular foramen, where it brieflycontacts the spinal part of the accessory nerve.
Immediately after leaving the skull, cranial part combineswith the vagus nerve at the inferior ganglion of vagus nerve (aganglion is a collection of nerve cell bodies).
The fibers from the cranial part are then distributed throughthe vagus nerve.
For this reason, the cranial part of the accessory nerve isconsidered as part of the vagus nerve.
By Khaleel Alyahya, PhD, MEd 39
HYPOGLOSSAL MOTOR
INTRODUCTION
It is the twelfth paired cranial nerve.
Its name is derived from ancient Greek, “hypo”meaning under, and “glossal” meaning tongue.
The nerve has a purely somatic motor function,innervating the majority of the muscles of the tongue.
By Khaleel Alyahya, PhD, MEd 41
ORIGIN & EXIT
The hypoglossal nerve arises from the hypoglossalnucleus in the medulla oblongata of the brain.
It then passes laterally across the posterior cranial fossa,within the subarachnoid space.
The nerve exits the cranium via the hypoglossal canal.
The nerve receives a branch of the cervical plexus thatconducts fibers from C1/C2 spinal nerve roots.
These fibers do not combine with the hypoglossal nerve – theymerely travel within its sheath.
It then passes inferiorly to the angle of the mandible, crossingthe internal and external carotid arteries, and moving in ananterior direction to enter the tongue.
By Khaleel Alyahya, PhD, MEd 42
SUMMARY
CRANIAL NERVES
By Khaleel Alyahya, PhD, MEd 44
4 pairs are mixed• trigeminal n. (5th)
• facial n. (7th)
• glossopharyngeal n. (9th)
• vagus n. (10th)
5 pairs are motor• occulomotor n. (3rd)
• trochlear n. (4th)
• abducent n. (6th)
• accessory n. (11th)
• hypoglossal n. (12th)
3 pairs are sensory• olfactory n. (1st)
• optic n. (2nd)
• vestibulocochlear n. (8th)
CRANIAL NERVES
By Khaleel Alyahya, PhD, MEd 45
CRANIAL NERVES
By Khaleel Alyahya, PhD, MEd 46
CRANIAL NERVES
By Khaleel Alyahya, PhD, MEd 47
Cranial Nerves Foramen Region Entered Components
I Cribriform plate Nasal cavity Sensory
II Optic canal Orbit Sensory
III Superior orbital fissure Orbit Motor
IV Superior orbital fissure Orbit Motor
V1
V2
V3
Superior orbital fissure
Foramen rotundum
Foramen ovale
Orbit
Pterygopalatine fossa
Infratemporal fossa
Mixed
VI Superior orbital fissure Orbit Motor
VII Internal acoustic meatus Temporal bone Mixed
VIII Internal auditory meatus Temporal bone Sensory
IX Jugular foramen Neck Mixed
X Jugular foramen - Mixed
XI Jugular foramen Neck Motor
XII Hypoglossal canal Neck Motor
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