HS2-12 Ear Flashcards
What are the three regions of the ear?
external ear
middle ear
inner ear
What is the function of the external ear?
collection of sound waves
What is the function of the middle ear?
transduction of sound waves from air to fluid of inner ear
What is the function of the inner ear? (3)
hearing
gravity
motion/acceleration
What are the three parts of the external ear?
auricle
external acoustic meatus
tympanic membrane
What is the composition of the auricle?
cartilaginous skeleton
The cartilaginous skeleton of the auricle is continuous with
the cartilage of the external acoustic meatus
What are the boundaries of the external acoustic meatus?
auricle → tympanic membrane
What is the tympanic membrane?
boundary between the external and middle ears
Why is the tympanic membrane actually not flat?
depressed inward by its attachment to malleus
What structures can be seen through the tympanic membrane?
manubrium (handle of malleus)
chorda tympani (from CN VII)
What is the best place for an incision in the tympanic membrane?
posterior-inferiorly, away from the chorda tympani and ossicles
What are the components of the middle ear?
tympanic cavity
tympanic antrum
pharyngotympanic tube
What is the lateral boundary of the middle ear?
tympanic membrane
The middle ear opens anteriorly into
the pharynx, via the pharyngotympanic tube
The middle ear opens posteriorly into
mastoid air cells
What are the three middle ear ossicles? Indicate their relative sizes and positions.
malleus (largest, most lateral)
incus (middle)
stapes
List the four structures associated with the malleus. (4)
head of malleus
manubrium of malleus = handle
tensor tympani muscle
chorda tympani nerve
Describe the position of the manubrium of the malleus.
embedded in tympanic membrane
Describe the position of the tensor tympani relative to the malleus.
attaches to manubrium of malleus
Describe the position of the chorda tympani relative to the malleus.
passes just medially to the manubrium and tympanic membrane
What are the three structures associated with incus?
body of incus
long limb
short limb
What does the body of the incus do?
articulates with head of malleus
What does the long limb of the incus do?
articulates w/ stapes at distal tip
What does the short limb of the incus do?
attaches to posterior wall of middle ear via ligament
What are the four structures associated with the stapes?
head to stapes
neck of stapes
two limbs
base
What does the head of the stapes do?
articulates with long limb of incus
What does the neck of the stapes do?
receives insertion of stapedius muscle
What do the two limbs of the stapes do?
the two limbs (anterior and posterior) extend to base
What does the base of the stapes do?
presses into oval window
What is the function of the ossicles?
transmit airborne sound waves or vibrations to aqueous medium of inner ear
How do the ossicles transmit sound waves to the aqueous humor of the inner ear?
act as pressure transducers to overcome different densities of air and water
What is the function of the stapedius?
restricts movement of ossicles, thus dampening loud sounds
Where is the stapedius located?
pyramidal eminence
The stapedius is innervated by
CN VII
Where is the tensor tympani found in the ear?
in the pharyngotympanic/auditory tube
The tensor tympani is innervated by
CN V3
What are the two series of canals found in the inner ear?
bony labyrinth
membranous labyrinth
List the features of the inner ear. (2)
small
completely encased in bone
The bony labyrinth of the ear is filled with
perilymph
How is the bony labyrinth connected to the middle ear?
via fenestra vestibuli (oval window)
and fenestra cochlea (round window)
What are the three regions of the bony labyrinth?
vestibule
cochlea
3 semicircular canals
What are the three semicircular canals?
anterior
posterior
lateral
Describe the positioning of the three semicircular canals.
all at right angles to each other
What is an ampulla (of the ear)?
an osseous structure at which a semicircular canal gets dilated
The membranous labyrinth is filled with
endolymph
What are the four components of the membranous labyrinth?
utricle
saccule
semicircular ducts
cochlear duct
What is the utricle?
large fluid filled sac that is attached to each semicircular canal
What is the saccule?
smaller fluid filled sac that is attached to cochlea
Give two examples of structures in the ear that are sensitive to changes in gravity.
utricle
saccule
What are the semicircular ducts (of the ear)?
fluid filled tubes inside each of the bony canals
What is the cochlear duct?
fluid filled tube inside bony cochlea
The bony cochlea is divided into what two spaces?
scala vestibuli (from fenestra vestibuli)
scala tympani (fenestra cochlea)
Sound sensitive hair cells are located in
the cochlear duct
The facial nerve exits the cranial cavity via
the internal acoustic meatus
What is the geniculate ganglion?
sensory ganglion associated with the facial nerve
What are the four branches of the facial nerve within the temporal bone?
greater petrosal nerve
nerve to stapedius
chorda tympani
motor nerves to muscles of facial expression
CN IX exits the cranial cavity via
the jugular foramen
The tympanic branch of CN IX re-enters the skull through
the floor of the middle ear cavity
What are the branches of CN IX within the temporal bone? (2)
sensory nerves
lesser petrosal nerve
What separates the bony and membranous labyrinths?
perilymph
How is balance sensed by the ear?
relative movement of fluids within the 3 semicircular canals
Describe the propagation of sound in the inner ear. (5)
oval window (from ossicles)
scala vestibuli
scala tympani
round window
as sound travels, it vibrates basilar membrane, which is what sends signals to the brain for hearing
What are the vessels found in the temporal bone? (3)
internal carotid artery
internal jugular vein
sigmoid sinus
List the pathway of sound through the external ear.
auricle (pinna) funnels sound through the
↓
external acoustic meatus, to the
↓
tympanic membrane
What provides general sensory innervation to the external ear? Draw a diagram. (4)
lesser occipitial (C2, C3) = posterior tip of external ear/auricle
great auricular (C2, C3) = auricle + earlobe
auricular branch of CN X = inferior portion of external acoustic meatus
auriculotemporal nerve (CN V3) = superior portion of external acoustic meatus
Label the following diagram of the pinna/auricle.
What is cauliflower ear?
hematoma between skin and cartilaginous skeleton
The cartilaginous portions of the ear houses what glands? (2)
ceruminous (wax) glands
sebaceous (oil) glands
Describe the pathway of sound vibrations in the middle ear.
tympanic membrane
↓
malleus
↓
incus
↓
stapes
↓
oval window
The tensor tympani attaches to what bone?
malleus
What muscle is responsible for opening the auditory/Eustachian tube?
tensor veli palatini, a muscle of the palate
What is the innervation of the tensor veli palatini?
CN V3
Broadly speaking, the semicircular canals are responsible for what function?
balance
Broadly speaking, the utricle is responsible for what function?
horizontal motion
Broadly speaking, the saccule is responsible for what function?
vertical motion
Describe the pathway of sound vibrations in the inner ear.
oval window (fenestra vestibuli)
↓
scala vestibuli
↓
scala tympani
↓
round window (fenestra cochlea)
What is the primary sensory structure located within the cochlea? Describe its function.
organ of Corti - its specialized hair cells sense vibrations of the basilar membrane, which are induced by fluid waves moving through scala vestibuli and scala tympani
