Cranial nerves



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ANATOMY EXAM 3 STUDY GUIDE – HEAD & NECK
CRANIAL NERVES


CN

Name

Origin

Foramen

Fibers

Branches

Functions

I

Olfactory

CNS ectoderm

Cribiform plate (ethmoid bone)

Sensory

SA





Transmit olfaction to brain

II

Optic

Diencephalon

Optic canal

Sensory

SA


Transmit visual info to brain

III

Oculomotor

Mesencephalon


Superior orbital fissure



Motor

GSE


GVE

GSE – motor innervation to all but 2 extraocular muscles

GVE – pregang parasymp fibers to ciliary ganglion cells



IV

Trochlear

Metencephalon or mes?

Superior orbital fissure

Motor

GSE


Motor innerv to superior oblique extraocular muscle

V


Trigeminal



Metencephalon



V1 – Superior orbital fissure

V2 – foramen rotundum

V3 – foramen ovale



Both

GSA


SVE

GVE

V1 – ophthalmic

V2 – maxillary

V3 – mandibular


GSA – extero and proprioceptive sensory nerve of face and anterior head (Great somatic sensory nerve)

SVE – motor innerv to striated muscles of mastication



VI

Abducens

Metencephalon

Superior orbital fissure

Motor

GSE





Motor innerv to lateral rectus extraocular muscle

VII

Facial

Metencephalon



Internal acoustic meatus

(for all branches)



Both

SVE


GVE

SA

GSA



GVA

Temporal


Zygomatic

Buccal


Mandibular

Cervical


SVE – striated muscles that originated from branchial arch 2 for facial expression

GVE – pregang parasymp fibers to pterygopalatine and submandibular ganglia cells

SA – taste buds of palate and anterior tongue

GSA – exteroceptive sensation from skin behind ear, in floor of external auditory meatus, outer surface of eardrum

GVA – interoceptive from nasal cavity mucosa, oral cavity and palate; glands controlled by pterygopalatine and submandibular glands

VIII

Vestibulocochlear

Metencephalon



Internal acoustic meatus

Sensory

SA





From sensory hair cells of vestibular labyrinth for balance and hearing

IX


Glossopharyngeal



Myencephalon



Jugular foramen



Both

GVA


GVE

SA

SVE



GSA

GVA – from posterior tongue (glossus) and pharynx, auditory/Eustachian tube, middle ear, inner eardrum surface

GVE – pregang parasymp fibers innervating otic ganglia

SA – fibers from taste buds of vallate papillae and posterior tongue

SVE – stylopharyngeus striated muscle of 3rd branchial arch

GSA – exteroceptive sensation from same skin patch supplied by facial nerve

X

Vagus

Myencephalon


Jugular foramen



Both

GVE


GVA

SVE


SA

GSA


GVE – pregang in parasymp motor path to glands of epiglottis and to cervical, thoracic, ab viscera

GVA – interoceptive info carried as afferent limb of visceral reflexes (poor sensation of pain, temp, touch, pressure in larynx and upper esoph lining)

SVE – motor innerv to striated muscle of palate, larynx, pharynx, upper esoph; from 4th and 6th branchial arches

SA – from taste buds at base of tongue, around epiglottis, in upper larynx

GSA – exteroceptive fibers from skin patch supplied by facial and glossopharyngeal and proprioceptive fibers from laryngeal muscles

XI

Accessory

Cervical spine


Jugular foramen





Motor

SVE





Cranial and spinal roots that converge at jugular foramen and diverge outside of skull; cranial nerve becomes accessory of vagus and spinal root supplies motor fibers to trapezius and sternocleidomastoid

XII

Hypoglossal

Myencephalon


Hypoglossal



Motor

GSE


GSA

GSE – intrinsic and extrinsic tongue muscles (excl. palatoglossus which gets SVE from CN X and XI); goes to glossus from below

GSA (and GSE) – supply geniohyoid and thyrohyoid muscles

C1 fiber – leaves hypglossal as uperior limb of ansa cervicalis and enters infrahyoid in anterior triangle



MUSCLES (53)


Grouping

Muscle

Action

Innervation

Vasculature

Face (9)

Buccinator


Presses cheek against molar teeth

Resists detention


Buccal branch of CN VII


Facial a.



Orbicularis oculi



Closing eyelids (squinting)



Facial nerve (CN VII)



Supraorbital a.

Supratrochlear a.

Infraorbital a.

Angular branch of facial a.


Depressor labii inferioris


Depresses lower lip



Inferior labial branch of facial a.

Mental a.


Zygomaticus major



Draws angle of mouth backward and upward (smile)

Transverse facial a.

Facial a.


Zygomaticus minor


Elevates upper lip



Transverse facial a.

Facial a.



Orbicularis oris



Closes lips; kissing muscle



Superior & inferior labial branches of facial a.

Mental a.

Infraorbital a.

Levator labii superioris



Elevates upper lip

Dilates nares (disgust)



Infraorbital a.

Superior labial branch of facial a.


Depressor anguli oris


Depresses angle of mouth



Inferior labial branch of facial a.

Mental a.


Levator anguli oris



Elevates angle of mouth medially (disgust)

Infraorbital a.

Superior labial branch of facial a.


Neck (1)

Digastric


Elevates hyoid and floor of mouth

Depresses mandible



Anterior belly – mylohyoid n. of V3 (CN V)

Posterior belly – facial n.



Anterior belly – submental a.

Posterior belly – occipital a.



Neck (3)


Posterior Triangle

Platysma

Tenses skin of inferior face

Depresses jaw



Facial nerve

Facial a.

Subclavius


Depresses clavicle


N. to subclavius



Thoracoacromial a.-clavicular branch

Omohyoid

Depresses/stabilizes hyoid bone


Ansa cervicalis



Transverse cervical a.

Neck (4)


Muscular Triangle

Infrahyoid muscles



Sternohyoid

Superior thyroid a.

Sternothyroid

Superior belly of omohyoid

Transverse cervical a.

Thyrohyoid

Elevates larynx

Depresses/stabilizes hyoid bone



Superior thyroid a.

Neck (2)


Carotid Triangle

Cricothyroid



Draws thyroid cartilage forward, lengthening vocal ligaments

External branch of superior laryngeal n. (branch of vagus n.)

Cricothyroid branch of superior thyroid a.

Thyrohyoid (also in muscular triangle)

See above

See above

See above

Neck (3)

Submandibular (digastric) Triangle

Digastric (ant and post bellies)

See above

See above

See above

Mylohyoid

Elevates hyoid bone and tongue when speaking and swallowing

N. to mylohyoid (branch of inferior alveolar n. from V3)

Mylohyoid branch of inferior alveolar a.

Stylohyoid

Elevates and retracts hyoid bone

Facial n. (CN VII)

Ascending pharyngeal a.

Neck (2)

Submental Triangle

Digastric muscles (sides)

See above

See above

See above

Mylohyoid (floor)

See above

See above

See above

Neck (5)


Structures deep to floor of triangle

Levator scapulae

Elevates scapula

Dorsal scapular n. (C5)

Dorsal scapular a.

Splenius capitus



Extends, laterally bends neck and head

Rotates head to same side



Dorsal primary rami of spinal n.

Deep cervical a.



Scalenes (3)

(posterior, middle, anterior)



Anterior & Middle – elevates first rib; flexes and laterally bends neck

Posterior – elevates second rib; flexes and laterally bends the neck



Anterior – brachial plexus (C5-C7)

Posterior – brachial plexus (C7-C8)

Middle – brachial plexus (C3-C8)

Ascending cervical a. (branch of thyrocervical trunk)



Neck (1)

Geniohyoid

--

C1 and C2 coursing with hypoglossal n. (CN XII)

Linguial a.

Submental a.



Head/Mastication (4)

Temporalis


Elevates and retracts mandible


Deep temporal n.



Anterior & posterior deep temporal arteries

Lateral pterygoid



Protracts and depresses the mandible

Moves mandible laterally


N. to lateral pterygoid


Pterygoid branch of maxillary a.



Medial pterygoid

Elevates and protracts mandible

Moves mandible laterally



N. medial pterygoid

Masseter

Elevates mandible, closes jaw

Anterior trunk of CN V3 (masseteric n)

Masseteric branch of maxillary a.

Pharynx (4)

Middle pharyngeal constrictor

Constricts walls of pharynx during swallowing



Pharyngeal branch of Vagus and Pharyngeal plexus


Ascending pharyngeal a.



Superior pharyngeal constrictor

Inferior pharyngeal constrictor



Ascending pharyngeal a.

Superior thyroid a.

Inferior thyroid a.


Stylopharyngeus

Elevates and dilates pharynx during swallowing and speaking

Glossopharyngeal n. (CN IX)

Ascending pharyngeal a.

Extraocular muscles of the

Orbit (7)



Levator palpebrae superioris

Elevates superior eyelid

Oculomotor n. (CN III)




Superior rectus

Elevates, ADducts and medially rotates eyeball

Medial rectus

ADducts eyeball

Inferior rectus

Depresses, ADducts and medially rotates eyeball

Inferior oblique

ABducts, elevates and laterally rotates eyeball

Superior oblique

ABducts, depresses and medially rotates eyeball

Trochlear n. (CN IV)

Lateral rectus

ABducts eyeball

Abducent n. (CN V)

Extrinsic muscles of the tongue (4)

Palatoglossus

Elevates posterior tongue, depresses soft palate, contricts isthmus of fauces

Pharyngeal branch of vagus n. (CN X)




Genioglossus

Depresses tongue, posterior fibers protrude tongue

Hypoglossal n. (CN XII)

Sublingual a.?

Hyoglossus

Depresses and retracts tongue

Dorsal lingual a.?

Styloglossus

Retracts and elevates tongue, aids initiation of swallowing

Intrinsic muscles of the tongue (4)

Superior longitudinal

Curls tongue upward, retrudes tongue

Deep lingual a. ?

Inferior longitudinal

Curls tongue downward, retrudes tongue

Transverse

Narrows and protrudes tongue

Vertical

Flattens and broadens tongue

Chin (1)

Mentalis

Elevates and wrinkles skin of chin and protrudes lower lip

Mandibular branch of facial nerve




Arytenoids (5)

Thyroarytenoid

Relaxes vocal ligament

Inferior laryngeal nerve (terminal part of recurrent laryngeal nerve, from CN X)




Posterior cricoarytenoid

Abducts vocal folds




Lateral cricoarytenoid

Adducts vocal folds




Transverse & oblique arytenoids

Adducts arytenoids cartilages (adducting intercartilagenous portion of vocal folds, closing posterior rima glottides)




Vocalis

Relaxes posterior vocal ligament while maintaining (or increasing) tension of anterior part






MNEMONICS/STUDY TIPS
LAB 1: TRIANGLES & ROOT OF NECK

Mnemonic – Carotid sheath contents: I see 10 CCs in the IV



  • I see = Internal Carotid artery

  • 10 = CN X (vagus nerve) (posterior)

  • CC = Common Carotid artery (medial)

  • IV = Internal Jugular Vein (lateral)

Relations of important nerves and vessels to the anterior scalene muscle

  • Structures passing anterior to anterior scalene

  • Structures passing posterior to anterior scalene

    • Brachial plexus

    • Subclavian a.


LAB 2: FACE, SCALP, & PAROTID REGION

Mnemonic – Motor branches of the facial nerve (CN VII): To Zanzibar By Motor Car OR Two Zebras Bit My Coccyx



  • Temporal

  • Zygomatic

  • Buccal

  • Marginal mandibular

  • Cervical

Mnemonic – Scalp nerve supply: GLASS

  • Greater occipital/Great auricular

  • Lesser occipital

  • Auriculotemporal

  • Supratrochlear

  • Supraorbital

Scalp blood supply

  • External carotid artery branches

    • Occipital

    • Posterior auricular

    • Superficial temporal

  • Internal carotid artery branches

    • Supraorbital

    • Supratrochlear

Mnemonic – Innervation of muscles

  • Facial nerve innervates muscles of facial expression

  • Mandibular nerve innervates muscles of mastication

Mnemonic – External carotid artery branches (in ascending order): Some Angry Lady Figured Out PMS

  • Superior thyroid

  • Ascending pharyngeal

  • Lingual

  • Facial

  • Occipital

  • Posterior auricular

  • Maxillary

  • Superficial temporal

Mnemonic – Scalp Layers: SCALP

  • Skin

  • Connective tissue

  • Aponeurosis

  • Loose areolar tissue

  • Pericardium


LAB 3: CRANIAL CONTENTS, REFLECTION OF HEAD, PHARYNX

Epidural hematoma



  • Anterior branch of middle meningeal artery (MMA) courses superiorly to cross pterion

  • Trauma to side of head may cause fractures of bones forming the pterion and consequently rupture the MMA located in this region

  • Since MMA course between dura and calvaria, in epidural space, hemorrhage in this location is called an epidural hematoma

Subdural hematoma

  • A blow to the head the jerks the brain inside the skull can cause the tearing of a cerebral vein, usually as it enters the superior sagittal sinus

  • Since cerebral veins course between the dura and arachnoid maters, a hemorrhage in this location is called a subdural hematoma

Clinical correlation – hematomas on CTs

  • Epidural hematomas: lens shape

  • Subural hematomas: crescent shape

  • Subarachnoid hematomas: conform to the shape of sulci

Arachnoid granulations

  • Projections of subarachnoid space that serve to return CSF to the venous system

  • On inner aspect of the calvaria you will notice small shallow depressions

  • The depressions are caused by the arachnoid granulations

Clinical correlation – Middle Meningeal artery

  • Its anterior branch crosses the area of the pterion

  • Fractures through this area result in tearing of the middle meningeal artery with consequence of an epidural hematoma

Mnemonic – foramen ovale contents: OVALE

  • Otic ganglion (just inferior)

  • V3

  • Accessory meningeal artery

  • Lesser petrosal nerve

  • Emissary veins

Foramina in posterior cranial fossa: all structures pass through temporal or occipital bones

  • Internal auditory meatus – CN VII, VIII

  • Jugular foramen – CN IX, X, XI, jugular vein

  • Hypoglossal canal – CN XII

  • Foramen magnum – spinal roots of CN XI, brain stem, vertebral arteries

Cisterns

  • Name of areas where subarachnoid space is enlarged

Dural folds

  • Tentorium cerebelli – separates the cerebellar lobe from the corresponding occipital pole of the cerebral hemisphere

  • Falx cerebelli – projects between cerebellar hemispheres

  • Falx cerebri – separates the two cerebral hemispheres

Mnemonic – cranial nerves: On Old Olympus’ Towering Top, A Fine Von German Vaulted And Hopped

  • Olfactory (I) – sensory

  • Optic (II) – sensory

  • Oculomotor (III) – motor

  • Trochlear (IV) – motor

  • Trigeminal (V) – both

  • Abducent (VI) – motor

  • Facial (VII) – both

  • Vestibulocochlear (VII) – sensory

  • Glossopharyngeal (IX) – both

  • Vagus (X) – both

  • Accessory (XI) – motor

  • Hypoglossal (XII) – motor

Mnemonic – cranial nerve modalities: Some Say Marry Money (or money matters) But My Brother Says Big Brains Matter More

  • Sensory

  • Motor

  • Both

Circle of Willis arteries supply:

  • ACA (anterior cerebral a.) – medial surface of brain, leg-foot area of motor and sensory cortices

  • MCA (middle cerebral a.) – lateral aspect of brain, Broca’s and Wernicke’s speech areas

  • Ant. Communicating a. – most common Circle of Willis aneurysm, may cause visual field defects

  • Post. Communicating a. – common area of aneurysm, may cause CN III palsy

Clinical correlation – signs of stroke

  • Stroke of anterior circle – general sensory and motor dysfunction, aphasia

  • Stroke of posterior circle – vertigo, ataxia, visual deficits, coma

Clinical correlation – pulsating exophthalmos

  • In fractures of the base of the skull, the ICA (internal carotid a?) may rupture within the cavernous sinus, forming an arteriovenous fistula

  • This creates reflux of blood from the cavernous sinus into the ophthalmic veins, which normally drain the orbital cavity

  • As a result, eye will appear protruded, engorged, and will pulsate

Mnemonic – structures passing through cavernous sinus

  • CN III, IV, V1, and V2 pass through it (in that order from superior to inferior) attached to the lateral wall, while CN VI is “free-floating” and not attached to the wall of the cavernous sinus

  • The cavernous portion ot eh ICA is also here

Memonic – foramina through which CN V exits: divisions of the CN V exit owing to Standing Room Only

  • Superior orbital fissure – V1

  • Foramen Rotundum – V2

  • Foramen Ovale – V3

Foramina in the middle cranial fossa – all structures pass through the sphenoid bone

  • Optic canal – CN II, ophthalmic artery, central retinal vein

  • Superior orbital fissure – CN III, IV, V1, VI, ophthalmic vein

  • Foramen rotundum – CN V2

  • Foramen ovale – CN V3

  • Foramen spinosum – middle meningeal a.


LAB 4: BISSECTION OF THE HEAD, PHARYNX & TEMPORAL REGION

Borders of the infratemporal fossa



  • Lateral – ramus of the mandible

  • Anterior – posterior aspect of the maxilla

  • Superior – inferior orbital fissure

  • Medial – pterygopalatine fossa and the lateral pterygoid of the sphenoid bone

  • Roof – greater wing of the sphenoid bone

Contents of the infratemporal fossa

  • Mandibular nerve (V3) – transmitted through the foramen ovale

  • Middle meningeal vessels

  • Sphenomandibular ligament, which attaches close to the spine of the sphenoid bone

  • Medial and lateral pterygoid muscles

Muscles of mastication – all innervated by CN V3

  • Lateral pterygoid

  • Masseter

  • Medial pterygoid

  • Temporalis

Mnemonic – branches of the maxillary artery: MIDtown Mice Bite People’s Smelly Instep

  • Middle meningela

  • Inferior alveolar

  • Deep temporal

  • Masseteric

  • Buccal

  • Posterior superior alveolar

  • Sphenopalatine (in the pterygopalatine fossa)

  • Infra orbital (in the pterygopalatine fossa)

Do not confuse buccal branch of CN V and VII

  • Buccal of V3 is sensory and GSA

  • Buccal of VII is motor to the buccinator muscle and SVE

Schematic for tympanic nerve pathway

Tympanic nerve arises from CN IX and emerges with it from the jugular foramen

Tympanic nerve enters the middle ear via the tympanic canaliculus in the petrous part of the temporal bone

Tympanic nerve forms the tympanic plexus on promontory of the middle ear

The lesser petrosal nerve arises as a branch of the tympanic plexus



Lesser petrosal nerve penetrates the roof of a tympanic cavity (tegmen tympani) to enter middle cranial fossa

Lesser petrosal nerve exits the cranium through the foramen ovale

Preganglionic parasympathetic (GVE) fibers from the lesser petrosal nerve synapse in the otic ganglion

Postganglionic fibers pass to the parotid gland via branches of the auriculotemporal nerve (branch of V3)
LAB 5: ORBIT, PTERYGOPALATINE FOSSA & NASAL REGION

Clinical correlation – Central retinal artery



Superior, Middle, and Inferior Meatus

  • Sphenoidal sinus drains into superior meatus

  • Middle meatus contains the Hiatus semilunaris

  • Nasolacrimal duct drains into inferior meatus


LAB 6: MOUTH, TONGUE AND LARYNX

Mneumonic – muscles innervated by the Hypoglossus nerve, CN XII:



  • All muscles with the root “-glossus” (except palatoglossus – CN X) are innervated by CN XII

Mneumonic – muscles inervated by Vagus nerve, CN X

  • All muscles with the root “-palat” (except tensor veli palatini – CN V2) are inervated by CN X







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