The Outer Ear Flashcards
What is the function of the outer ear?
to collect, resonate and localize sound as well as provide protection
What frequencies does the outer ear resonate?
2000Hz - 7000Hz
What is the resonant frequency of the EAM?
~2700 Hz
The pinna forms at the same time as the _________ during embryological development
kidneys
At what age does the pinna reach adult size?
~8 years old
What is anotia?
an absent pinna
what is microtia?
a very small pinna
what is macrotia?
a very large pinna
what is meltier?
displacement of the pinna
What is the name of the surgery for pinning back ears?
otoplasty
What are the two main components of the outer ear?
1) pinna
2) EAM
Describe the outer 1/3 of the EAM
skin-covered cartilage
has sebaceous glands and follicles
Describe the inner 2/3 of the EAM
skin-covered bone with no follicles or glands
What is the name of the place where the outer and inner portions of the EAM meet
the osseocartilaginous junction
Where your osseocartilaginous junction is, is often where your __________ joint is located
temperomandibular joint
T or F the condyle sits bellow the OC junction at rest
True
If the condyle presses into the OC junction, where is the pain often felt?
referred pain felt in the ear
What determines the colour of your ear wax?
it is genetically based - based on your melanin
Earwax grows in an _______ fashion
outward
Cleaning your ears ________ the production of ear wax
increases
What is atresia of the ear canal?
full closure of the ear canal
What is stenosis of the ear canal?
narrowing or collapsing of the EAM
Stenosis of the EAM is especially common in what population?
the elderly
What is external otitis?
infeciton in the skin lining of the outer ear, AKA swimmers ear
Does stenosis usually involve real world hearing loss?
no
What are the 5 main components of the middle ear?
1) tympanic membrane
2) ossicles
3) middle ear space
4) Eustachian tube
5) Middle ear muscles
Describe the structure of the tympanic membrane (TM)
- concave, disk like structure
- area is 63-90 mm2
- width is 0.7mm
- very rich in blood supply
What are the three layers of the TM
- epidermal
- fibrous
- mucous
The tympanic membrane is held in position by what structure?
the tympanic annulus
Movement of the TM as little as __________________ can stimulate hearing
one billionth of a cm
T or F a healthy TM is translucent
true
What is it called when there is a hole in the tM
perforation
How does scar tissue affect the TM?
it makes it more flaccid
What is myringitis?
inflammation of the TM
What is a tympanoplasty?
patching of a perforation in the TM
What is the function of the ossicles?
they conduct TM vibration to the inner ear, and ‘amplify’ sound
T or F: the malleus moves on its own and the incus and stapes move as one
F - the malleus and incus move as one, the stapes moves on its own
What do we call it when the ossicles have been displaced from each other?
disarticulation
What is otosclerosis?
starts when spongy bone forms over the stapes, and then it hardens and the footplate becomes fixed, causes conductive hearing loss
Please describe the middle ear
air filled (2cm3) and has a mucous membrane lining
The middle ear is connected to the nasopharynx via the _________
eustachian tube (ET)
Where is the ET located?
it sits above the tonsils
The ET is ______ at rest
closed
what muscle is responsible for opening the ET?
the tensor veil palatini
How often does the ET open during waking?
once/min
How often does the Et open during sleep?
once/ 5 min
The ET opens during …
yawning, sneezing, swallowing or excessive nasal pressure
Explain the differences in ET structure between adults and children?
- In adults the ET sits at a 30 degree angle, in children it is more horizontal, ~10 degrees
- Children still have adenoids that can block the flow of fluid
- Children are prone to ET dysfunction
____% of the time, fluid in the middle ear of children is not used by infection
50%
Air pressure of the middle ear must ______ the air pressure of the EAM
match
What is the only natural way to maintain pressure equalization?
the eustachian tube
When does the ET lock shut?
at extreme pressures
What happens when the ET locks shut?
- great pain occurs
- at risk for TM rupture
- at risk for middle ear effusion
What is meant by a patulous ET
the ET remains open
What two groups of people are prone to patulous ET
- body builders (from clenching)
- people with bulimia
______% of children have had otitis media by age 3, and _____% by age 5
30%
75%
25-50% of the time, otitis media is _______, meaning it doesn’t have any noticeable symptoms
‘silent’
List as many risk factors as you can for otitis media (OM)
- age 18mos to 3years
- bottle feeding
- attendance in group day care
- exposure to tobacco smoke
- cranio-facial involvement
- family history
- premature birth
- season
T or F: the reason the risk for OM is higher when the infant is bottle fed is because they are lacking nutrients from the breast milk
no it is more likely the position of the baby during the feeding
List the 3 categories of OM
- serous OM
- acute OM
- chronic OM
Describe serous OM
air in the middle ear space is replaced by any type of fluid other than true pus
What can cause serous OM?
- ET dysfunction
- Mucous secretions blown through the ET
- Allergies, upper RT infections, second hand smoke
Describe acute OM
the middle ear is filled with bacteria or there is a viral infection
-characterized by a rapid onset, fever, pain, irritability, disruption in sleeping or eating patterns
Describe chronic OM
any fluid remains for an extended period of time (>8 weeks)
List the possible treatments of OM
- wait and see
- antibiotics
- nasal spray
- myringotomy with/without tubes
- non-medical
When a child has OM, when is waiting and seeing the right treatment?
children with no speech & language delays can be observed with 3 months with no detriments
-children with persistent effusion or speech and language delays should be referred
When should antibiotics be used to treat OM? Are they always effective
antibiotics should be used when there is an actual infection
-antibiotic therapy is minimally effective
What is the function of the middle ear?
- carries vibration from the outer to inner ear
- overcomes loss of sound energy when sound passes from air to fluid
When sound travels from air to water how much of sound energy is reflected? give answer in percent and dB
99.9%
30dB
What are the three ways the middle ear amplifier matches the energy loss from air-fluid
- leverage action of ossicles
- vibrating area of TM is 17x that of oval window
- curved shape of TM focuses movement on the malleus
The middle ear amplifier results in a pressure increase _________ at the oval window. This is a _____ dB increase
23
30dB
What are cholesteatomas
benign mass growing in middle ear space due to chronic build up of non-infection based fluid
What is petrositis?
infection of the mastoid air cells medial to the inner ear
T or F: skull fractures can lead to middle ear problems
True
What are the two muscles of the middle ear
- stapedius
- tensor tympani
The middle ear muscles can reduce intensity by as much as _____ dB
15 dB
