Ears Class notes Flashcards
Overal function of ear
hearing; equilibrium
External ear terminates at?
tympanic membrane
Outer 1/3 of ear
Cartilage
Inner 2/3 ear
through temporal bone
TM separates
external and middle ear
Lymphatic drainage of external ear flow to the
parotid, mastoid, and superficial cervical
nodes
Middle ear description
Air-filled cavity inside temporal bone
Eustachian tube—connects middle ear with nasopharynx and allows passage of air.
Normally closed—opens with swallowing or yawning.
Middle ear: Three functions:
Conducts sound vibrations from outer to inner ear.
Protects inner ear by reducing sound amplitude.
Eustachian tube allows equalization of air pressure on each side of the TM so TM does not rupture.
Inner ear description & function
Contains bony labyrinth which holds sensory organs for equilibrium and hearing.
Cochlea—contains central hearing apparatus.
Function of hearing—3 levels
peripheral; brainstem; cerebral cortex
Peripheral level
Sound transmission
Vibrations converted into electrical impulses for analysis by the brain.
Electrical impulses conducted by the auditory portion of CN VIII to the brainstem
Brainstem function
binaural interaction—locating direction of sound in space—identifying the sound
Cerebral cortex
interprets the meaning of the sound and begins the appropriate response.
Normal pathway of hearing is by
Alternative route is by
AC
BC
Conductive loss caused by
impacted cerumen; foreign body; perforated TM; pus/blood in middle ear; otosclerosis (↓ mobility of the ossicles).
Conductive loss can be treated by
increasing amplitude.
Sensorineural (perceptive) loss caused by
patho of inner ear, CN VIII, or auditory areas of cerebral cortex; gradual nerve degeneration that occurs with age.
Three semicircular canals (labyrinth) in inner ear function
input to your brain about your position in space
Inflamed labyrinth causes
vertigo-impaired signal to brain
DC: infants & children
Eustachian tube shorter, wider, more horizontal—easier for pathogens from nasopharynx to get to the middle ear, causing otitis media
Increased risk for middle ear infection:
Absence of breastfeeding first 3 mo. of life Exposure to secondhand smoke Daycare attendance Male sex Pacifier use Seasonality (fall, winter) Bottle feeding in the supine position
SD: ear symptoms–> must ask?
ask about recent URI, history of ear infections
Otalgia
Ear pain that can arise from external or internal ear
Otorrhea
Drainage from ear
can be purulent, sanguineous
Tinnitus definition
Phantom sound
originates from within person
Tinnitus causes
Cerumen impaction
Middle ear infection
other ear disorders
First episode of OM that occurs within first 3 mo. of life increases risk
recurrent OM
Infants at risk for hearing deficit are those who were/have:
Exposed to maternal rubella
Exposed to maternal ototoxic drugs in utero
Premature infants
Low birth weight infants
Trauma or hypoxia at birth
Congenital liver or kidney disease
Children at risk for hearing deficit are those who have:
Meningitis Measles Mumps OM Any illness with persistent high fever
Incidence and severity of OM increased in indigenous children from
No. America, Australia, New Zealand, and Northern Europe.
Aging adult changes
May have increased amount and drier cerumen, which become impacted
Presbycusis definition and causes
hearing loss in 60% older than 65 years; gradual sensorineural loss caused by nerve degeneration in the inner ear
OD: Clues to hearing loss
a) Lip reading
b) Frowns, leans forward to hear
c) Postures head to catch sound
d) Misunderstands questions
e) Frequently asks you to repeat questions
f) Acts irritable or startled when you raise your voice
g) Speech is garbled
h) Inappropriately loud voice
i) Flat, monotonous tone of voice
Testing hearing acuity in infants and children:
With loud noise—
Newborn hearing testing
startle (Moro) reflex; acoustic blink reflex
Hearing testing in 3 to 4 mo:
acoustic blink reflex; Infant stops moving and appears to “listen”.
Stops sucking.
Quiets if crying.
Cries if quiet
Hearing testing in 6-8 mo
Infant turns head to localize
Hearing testing in preschool/school aged
Audiometry
