Cranial nerves Study Guide and notes

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 thyroid a.
	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.
Neck (2) Carotid Triangle	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
Neck (2) Submental Triangle	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	Pterygoid branch of maxillary a.
	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			Ascending pharyngeal a.
	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		Dorsal lingual a.?
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

Vagus n.
Phrenic n.
Thyrocervical trunk branches
Subclavian v.

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

It’s occlusion leads to instant and total blindness of the affected eye

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

Source: http://www.bumc.bu.edu/mybusm/files/2009/08/anatomy-exam-3-study-guide-updated.doc

Web site to visit: http://www.bumc.bu.edu

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Cranial nerves Study Guide and notes

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Cranial nerves Study Guide and notes

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