Lecture 4.1 - The Skull and Overview of Cranial Nerves

Question 1

What is the neurocranium?

Answer 1

• houses brain
• • calvaria (skullcap)
• • cranial base (basicranium)

Question 2

What is the viscerocranium?

Answer 2

• facial bones that form:
• • orbits
• • nasal cavities
• • upper jaw
• • lower jaw (mandible)

Question 3

What are the bones of the neurocranium and their location?

Answer 3

• frontal (forehead)
• parietal (2)
• temporal (2)
• • mastoid process, styloid process, external acoustic meatus
• occipital (back of head)
• • external occipital protuberance
• sphenoid (butterfly)
• ethmoid

Question 4

What are the sutures of the neurocranium and which bones do they split?

Answer 4

• Coronal: frontal and parietal
• Lambdoid: parietal and occipital
• Sagittal: R & L parietal
• Squamous: parietal and temporal

Question 5

What are the intersections of the cranial sutures?

Answer 5

• Bregma: sagittal and coronal
• Lambda: lambdoid and sagittal
• Pterion: frontal, parietal, temporal, sphenoid
• Asterion: parietal, occipital, temporal
• Nasion: frontal and nasal bones

Question 6

What occurs if the pterion is fractured?

Answer 6

Fracture to pterioni may tear the middle meningeal artery leading to an epidural hematoma

Question 7

Where are the Glabella? Vertex? Inion?

Answer 7

• Glabella: most anterior part of forehead
• Vertex: superiormost post of neurocranum
• Inion: most prominent point of external occipital protuberance

Question 8

What bones make up the anterior fossa?

Answer 8

• frontal bone
• ethmoid bone
• part of sphenoid bone (lesser wing)

Question 9

What bones make up the middle fossa?

Answer 9

Sphenoid (greater wing/body)
Temporal bone (squamous and petrous part)

Question 10

What bones make up the posterior fossa?

Answer 10

Temporal bone (petrous part)
Occipital bone

Question 11

What holes are in the anterior fossa?

Answer 11

cribriform plate (ethmoid)

Question 12

What holes are in the middle fossa?

Answer 12

All sphenoid

• optic foramen
• superior orbital fissure
• foramen rotundum/ovale/spinosum/lacerum

Question 13

What holes are in the posterior fossa?

Answer 13

• internal acoustic meatus (temporal)
• jugular foramen (between temporal and occipital)
• hypoglossal canal (occipital)
• foramen magnum (occipital)

Question 14

What are the characteristics for the sphenoid bone?

Answer 14

• it is a key in cranial skeleton
• it articulates with 8 bones
• has a central body, 2 wings laterally and 2 processes inferiorly

Question 15

Where is the pituitary gland?

Answer 15

within the hypophysis in the sella turcica (body of sphenoid)

Question 16

What are the bones of the viscerocranium?

Answer 16

• lacrimal (2)
• nasal (2)
• zygomatic (2)
• palatin (2)
• inferior nasal conchae (2)
• mandible
• vomer

Question 17

What bones form the orbit wall?

Answer 17

• frontal bone
• ethmoid bone
• lacrimal
• maxilla
• palatine
• zygomatic
• sphenoid (greater/lesser wing)
• superior/inferior orbital fissure

Question 18

What bones form the nasal cavity?

Answer 18

• nasal
• maxillae
• inferior nasal conchae
• ethmoid (middle/superior nasal conchae and perpendicular plate)
• vomer

Question 19

What are the other important holes in the face?

Answer 19

• Supraorbital notch/foramen (frontal): V1 trigeminal exits (ophthalmic nerve) supplying forehead sensory
• Infraorbital foramen (maxilla): V2 trigeminal exits supplying mid face sensory
• Mental foramen (mandible): V3 trigeminal supplying mandible sensory

Question 20

What are cranial nerves?

Answer 20

• nerves originating from brain or brainstem and exiting through foramina or fissures in the cranium
• 12 pairs (CN1 - XII - anterior to posterior)

Question 21

What do cranial nerves variously carry nerve fibers for?

Answer 21

• somatic motor (movement of eyes, mastication, deglutition, respiration, vocalization, facial expression)
• general sensory (pain, pressure, temperature) to tissues
• special sensory (olfaction, vision, gustation, audition, equilibrium)
• parasympathetic motor (to lacrimal, salivary, and mucous glands and smooth muscles of eye)

Question 22

Olfactory Nerves (CN, Function, Innervation, Exit)

Answer 22

CN I
F: special sensory - smell
I: olfactory epithelium of superior nasal cavity
E: cribriform plate of ethmoid

Question 23

Optic Nerves (CN, Function, Innervation, Exit)

Answer 23

CN II
F: special sensory - vision
I: retina of the eye
E: optic foramen (sphenoid bone)

Question 24

What are the visual fields of retina?

Answer 24

• optic nerve of each eye: temporal field, nasal fidl
• optic chiasm: decussation of temporal fields of view
• optic tracts: left (information from R fields of both eyes), right (information from left fields of both eyes)

Question 25

What does defect of right optic nerve cause?

Answer 25

blindness of one eye (anopsia)

Question 26

What is does defect of optic chiasm cause?

Answer 26

loss of peripheral visual fields (bitemporal hemianopsia; "tunnel vision"

Question 27

What does defect at right optic tract cause?

Answer 27

loss of visual field on opposite side (homonymous hemianopsia)

Question 28

Oculomotor nerve (CN, Function, Innervation, Exit)

Answer 28

CN III Function/Innervates: - somatic motor: -- all eye muscles except superior oblique (CN IV) and lateral rectus (CN VI) -- levator palpebrae superioris (muscle that raises eyelids) - parasympathetic - constriction of pupils; change shape of lens (accommodation) Cranial Exit: superior orbital fissure of sphenoid

Question 29

What does complete paralysis of CN III cause?

Answer 29

leads to dilated pupils, ptosis (droopy eyelids), and inability to move eye upward, downward, and medially

Question 30

Trochlear Nerves (CN, Function, Innervation, Exit)

Answer 30

CN IV F: somatic motor - eye movement I: superior oblique muscles of the eye E: superior orbital fissure of sphenoid

Question 31

What occurs when trochlear nerve is injured?

Answer 31

patient unable to look downward and inward; says "has difficulty walking downstairs"

Question 32

Abducent/Abducens Nerve (CN, Function, Innervation, Exit)

Answer 32

CN VI F: somatic motor - eye movement I: lateral rectus muscle E: superior orbital fissure of sphenoid

Question 33

What occurs when abducent nerve is injured?

Answer 33

patient has medial strabismus (deviation); unable to abduct the eye

Question 34

What are the 3 division of Trigeminal nerve and its CN number?

Answer 34

CN V V1 ophthalmic V2 maxillary V3 mandibular

Question 35

V1 Ophthalmic division of Trigeminal nerve (Function, Innervation, Exit)

Answer 35

F: general sensory I: conjunctiva and cornea of eye, nasal cavity, skin of scalp, forehead, eyebrows, upper eyelid, and part of external nose E: superior orbital fissure of sphenoid

Question 36

What branches of V1 are seen in orbit?

Answer 36

lacrimal nerve and frontal nerve (divides into supraorbital nerve and supratrochlear nerve)

Question 37

V2 Maxillary division of Trigeminal nerve (Function, Innervation, Exit)

Answer 37

F: general sensory I: lower eyelid, upper lip, upper gums, upper teeth, cheek, palate, and pharynx E: foramen rotundum (sphenoid)

Question 38

What are the important branches of V2?

Answer 38

superior alveolar nerve and infraorbital nerve

Question 39

V3 Mandibular division of Trigeminal nerve (Function, Innervation, Exit)

Answer 39

F: general sensory and somatic motor Innervation: - Sensory - skin over mandible, lower gums, lower teeth, lower lip, anterior 2/3 of tongue - Motor - muscles of mastication (temporalis, masseter, medial/lateral pterygoids), anterior digastric and mylohyoid muscles, tensor veli palatini m. E: foramen ovale (sphenoid)

Question 40

What are the important branches of V3?

Answer 40

``` lingual nerve (tongue) inferior alveolar nerve (lower teeth/gums) mental nerve (chin) ```

Question 41

Facial Nerves (CN, Function, Innervation, Exit)

Answer 41

CN VII Function/Innervates: - parasympathetic -- lacrimal glands (tears) -- mucous glands of nasal cavity, pharynx, and palate -- submandibular/sublingual salivary gland - special sensory - taste receptors on anterior 2/3 of tongue Cranial Exit: - through the internal acoustic meatus (temporal bone) - out of the stylomastoid foramen (temporal bone)

Question 42

Vestibulocochlear Nerves (CN, Function, Innervation, Exit)

Answer 42

CN VIII (Acousticovestibular) F: special sensory - balance and hearing I: Vestibule (receptors for motion and balance) and Cochlea (hearing receptors) E: internal acoustic meatus of temporal bone

Question 43

How can Vestibulocochlear nerve be damaged? What are the symptoms?

Answer 43

Can be injured in fractures of middle cranial fossa - cochlear n. leads to tinnitus (ringing, buzzing) and deafness - vestibular n. - vertigo and nystagmus

Question 44

Glossopharyngeal nerve (CN, Function, Innervation, Exit)

Answer 44

CN IX Function/Innervates: - general sensory: posterior 1/3 of tongue, pharynx, palate, tonsil - special sensory: posterior 1/3 of tongue (taste), carotid body (monitors blood oxygen levels), carotid sinus (monitors blood pressure) - parasympathetics: parotid gland (salivary) - somatic motor: stylopharyngeus m. Cranial exit: jugular foramen

Question 45

Vagus Nerves (CN, Function, Innervation, Exit)

Answer 45

CB X Function/Innervation: - motor: muscles of pharynx, larynx, and palate (except tensor veli palatini) - general sensory: pharynx, tongue - special sensory: taste to area around epiglottis - parasympathetics (and sensory): abdominal and thoracic viscera Cranial exit: jugular foramen

Question 46

What cranial nerves are part of gag reflex?

Answer 46

Glossopharyngeal: sensory part of gag reflex Vagus: motor part of gag reflex

Question 47

Spinal Accessory Nerve CN, Function, Innervation, Exit)

Answer 47

CN XI F: motor I: sternocleidomastoid m. and trapezius m. E: jugular foramen

Question 48

Hypoglossal Nerve CN, Function, Innervation, Exit)

Answer 48

F: motor - tongue muscles I: all muscles with "gloss" in name (except palatoglossus m.) E: hypoglossal canal (occipital)

Question 49

Name all 12 cranial nerves

Answer 49

``` Olfactory Optic Oculomotor Trochlear Trigeminal Abducent Facial Vestibulocochlear Glossopharyngeal Vagus Accessory Hypoglossal ```