Which bone protects the organs of hearing and balance?
Temporal bone
What kind of nerve fibres innervate the ear?
Special sensory nerves
Which cranial nerves are most responsible for hearing and balance?
CN VII (Facial nerve)
CN VIII (Vestibulocochlear nerve)
What is the pterion?
Intersection of the
FRONTAL, PARIETAL, TEMPORAL and SPHENOID sutures
also the thinnest part of the skull
What is the thinnest part of the skull and which bone is it found on?
Pterion
Temporal bone
What is the lower part of the temporal bone called and why?
Petrous part
harder than the upper part
What part of the temporal bone forms the outer opening of the ear?
External acoustic meatus
What is the pointy projection at the lower part of the temporal bone which can be palpated behind the ear?
Mastoid process
What is the thin projection from the temporal bone which acts as the insertion for some muscles of the tongue and pharynx?
Styloid process
Which process attaches the temporal bone to the zygomatic bone?
Zygomatic process
What are the three important processes of the temporal bone?
Mastoid process
Styloid process
Zygomatic process
Which bone forms the hard palate?
Palatine bone
Which bones make up the floor of the anterior cranial fossa?
Frontal, ethmoid and sphenoid bones
Which bones make the floor of the middle cranial fossa?
Sphenoid and temporal bones
Which bones make up the floor of the posterior cranial fossa?
Temporal and occipital bones
Do the parietal bones make up the floors of any cranial fossa?
No (found on the walls)
Where does CN I exit the cranial cavity?
Cribriform plate
Where does CN II exit the cranial cavity?
Optic canal
Where do CN III, IV, V1 and VI exit the cranial cavity?
Superior orbital fissure
Where does CN V2 exit the cranial cavity?
Foramen rotundum
Where does CN V3 exit the cranial cavity?
Foramen ovale
Where do CN VII and VIII exit the cranial cavity?
Internal acoustic meatus
Where do CN IX, X and XI exit the cranial cavity?
Jugular foramen
(so does the internal jugular vein)
Where does CN XII exit the cranial cavity?
Hypoglossal canal
What are the three general parts of the ear
External ear
Middle ear
Internal ear
The external ear goes from the ___ to the ___ ___.
auricle
tympanic membrane
What joins the auricle to the external tympanic membrane?
External acoustic meatus
What is the purpose of the external ear?
Collects sound waves and conveys them to tympanic membrane
The middle ear goes from the ___ ___ to the ___ ___.
tympanic membrane
oval window
Apart from the tympanic membrane, ossicles and oval window, what other important structure is found in the middle ear?
Eustachian tube
What is the purpose of the middle ear?
Amplifies sound
The internal ear goes from the ___ ___ to the ___ ___ ___.
oval window
internal acoustic meatus
What is the purpose of the internal ear?
Turns sound waves into action potentals
What is the external ear called?
Auricle
What is the posterior outer rim of the ear called?
Helix
What is the rim of the ear next to the external acoustic meatus called?
Tragus
Which nerves supplies sensory fibres for most of the posterior helix?
What is the exception?
C2 and C3
Tiny bit by CN VII
Which cranial nerve supplies most of the inner helix and the external acoustic meatus?
CN V3 - mandibular division
Which two cranial nerves supply the external acoustic meatus with sensory fibres?
CN V3
CN X
Which lymph nodes drain the superior half of the auricle (facing forward)?
Parotid lymph nodes
Which lymph nodes drain the superior half of the auricle (facing posteriorly)?
Mastoid lymph nodes
Which lymph nodes drain the lower half of the auricle and the ear lobe?
Superficial cervical nodes
Where does all lymph from the auricle eventually drain?
Deep cervical lymph nodes
The external ear is made out of the temporal bone and elastic ___.
cartilage
What is the technical name for the ear canal?
External acoustic meatus
Which type of gland produces earwax in the external acoustic meatus?
Ceruminous glands
What name is given to a medical device used to look inside the ear?
Otoscope / auriscope
In a child, what shape is the external acoustic meatus?
Short and straight
In an adult, what shape is the external acoustic meatus?
Curved
What structure do you want to look at with an otoscope?
Tympanic membrane
What are some important structures of the tympanic membrane?
Umbo (depressed part)
Pars flaccida (thin, superior part)
Pars tensa (thick, inferior part)
Which cranial nerves supply sensory fibres to the
a) external
b) internal surfaces of the tympanic membrane?
a) CN V3 - mandibular division
b) CN IX - glossopharyngeal nerve
What areas of the head and neck does CN IX supply?
Middle ear
Eustachian tube
Nasopharynx
Oropharynx
Tonsils
CN __ supplies the middle ear, eustachian tube, nasopharynx and oropharynx with sensory nerve fibres.
CN IX
What is the collective name for the three bones of the inner ear?
Auditory ossicles
What are the three auditory ossicles called?
Malleus (mallet)
Incus (anvil)
Stapes (stirrup)
Which auditory ossicle looks like an anvil?
Incus
Which auditory ossicle looks like a mallet?
Malleus
Which auditory ossicle looks like a stirrup?
Stapes
Which type of joint connects malleus, incus and stapes?
Synovial joint
What creates the umbo of the tympanic membrane?
Handle of the malleus pressing on it
What space is found superior to the tympanic membrane?
Epitympanic recess
What space is found posterior but not inferior to the tympanic membrane?
Tympanic cavity
Which tube is found in the tympanic cavity and connects the middle ear to the nasopharynx?
Eustachian tube
Which cranial nerve supplies the middle ear and the nasopharynx?
CN IX
Why can pharyngitis or tonsilitis cause earache?
Referred pain as CN IX supplies both areas
Apart from the eustachian tube, what other structure in the epitympanic recess is a tube which connects to the mastoid antrum?
Aditus
Through which structure does the facial nerve travel to the stylomastoid foramen?
Internal acoustic meatus
Facial canal
Where in the brainstem does the facial nerve arise?
Pons-medullary junction
Which cranial bone is the internal acoustic meatus found in?
Temporal bone
The facial nerve travels through the internal acoustic meatus and facial canal before emerging where?
Stylomastoid process
Which tube connects the internal acoustic meatus to the stylomastoid process?
Facial canal
What is a branch which comes off the facial nerve?
What does it supply?
Chorda tympani
Taste to anterior 2/3rds tongue
Parasympathetics to submandibular and sublingual glands
The facial nerve innervates a muscle which stops the stapes from vibrating too much - what is it called?
Stapedius
What are the functions of the facial nerve?
PARASYMPATHETIC - lacrimal, submandibular and sublingual glands
SOMATIC MOTOR - muscles of facial expression
SOMATIC SENSORY - tiny part of auricle
Which other cranial nerve does the chorda tympani hitch a ride with to reach the submandibular and sublingual glands?
CN V3
Lingual nerve
What are some of the muscles of facial expression?
Frontalis
Orbicularis oculi
Lip elevators
Orbicularis oris
How can the motor function of CN VII be tested?
Ask patient:
frown
close eyes tightly
smile
puff out cheeks
Which ganglion do lots of CN VII fibres synapse at in the facial canal?
Geniculate ganglion
Which part of the ear is responsible for turning sound waves into action potentials?
Internal ear
Which cranial nerve is responsible for hearing and balance?
CN VIII - Vestibulocochlear nerve
Which parts of CN VIII are responsible for
a) hearing
b) balance?
a) Cochlear nerve
b) Vestibular nerve
The vestibular nerve is responsible for ___.
The cochlear nerve is responsible for ___.
balance
hearing
Through which structure do CN VIII fibres travel to the brain?
Internal acoustic meatus
What is the complicated structure found in the internal ear which contains the cochlea and semicircular canals?
Otic capsule
What are the spaces within the otic capsule called?
Labyrinths
What are the two labyrinths found within the otic capsule?
Bony labyrinth
Membranous labyrinth
The ___ labyrinth is found within the ___ labyrinth.
membranous WITHIN bony
What kind of fluid is found within the
a) bony
b) membranous labyrinths?
a) Perilymph
b) Endolymph
What fluid allows the membranous labyrinth to float within the bony labyrinth?
Perilymph
Which structure of the otic capsule looks like a snail’s shell?
Cochlea
What is the apex of the cochlea called?
Cupula
Which nerve travels in the cochlea?
What is it responsible for?
Cochlear nerve
Hearing
What are the long balloon-like structures which contain endolymph and the vestibular nerve?
Semicircular canals
What is the path of soundwaves in the internal ear?
1. Sound wave vibrate tympanic membrane
2. Auditory ossicles vibrate
3. Stapes vibrates the oval window
4. Pressure waves in PERILYMPH activate HAIR CELLS
5. Hair cells release neurotransmitters and an action potential is conveyed to the brain by the cochlear nerve
6. Round window DAMPENS pressure waves
What are the two windows found in the otic capsule?
What are they for?
Oval window and round window
Oval window is where the stapes vibrates and triggers a pressure wave
Round window is where the leftover pressure wave is dampened after an action potential has been generated
Where do CN VII and CN VIII connect to the brainstem?
Pons-medullary junction
The cochlear nerve and therefore hearing is controlled by the (cochlea / semicircular canals).
cochlea
The vestibular nerve and therefore balance is controlled by the (cochlea / semicircular canals).
semicircular canals
If you had an acoustic neuroma (tumour in the internal acoustic meatus) what symptoms would be produced on behalf of
a) CN VII
b) CN VIII?
a) Loss of function of muscles of facial expression, dry eyes (reduced lacrimation), dry mouth (reduced submandibular / sublingual secretions), loss of sensation at that little bit of the auricle, loss of taste
b) Loss of hearing, loss of balance