Week 6.0 - Ear Flashcards
Name the components of the middle ear
- Auditory ossicles (malleus, incus, stapes)
- Mastoid air cells
- Tympanic cavity
- Eustachian tube
- Tensor typani
- Stapedius
Name the components of the inner ear
- Semicircular canals
- Vestibular labyrinth
- cochlear
Why is the shape of the pinna significant?
-Grooves act to funnel sound and amplify into EAC to vibrate tympanic membrane
How do you examine the ear?
- Compare both sides at front, sides, behind and inside
- In adults pull up, back and out
- In children pull down, back and out
What is a pinna haematoma? Why is it serious?
- Haematoma (collection of blood) between cartilage and perichondrium
- Prevents oxygenation of cartilage resulting in avascular necrosis
Name 3 common conditions of the external auditory canal
- Foreign body
- Conduction block by wax
- Otitis externa
Describe the tympanic membrane
- Waterproof barrier consisiting of pars flaccida and pars tensa with the fibres arranged from midline outwards
- Handle of malleus pressed on posterior of membrane
- Umbo
What is a tympanic perforation? Give the most common 2 causes
- Hole in the tympanic membrane
- Can be central or subtotal
- Often caused by trauma or secondary to infection
What is the difference between pars flaccida and pars tensa of the tympanic membrane?
-Pars flacida fibres are haphazerdously arranged
Name the auditory ossicles
-Malleus, stapes and incus
How are the auditory ossicles arranged?
-Handle of malleus presses into tympanic membrane, head of malleus bound to body of incus, long process of incus attaches to head of stapes, foot plate of stapes plugs into oval window of inner ear
What is the result of dysfunction of the eustachian tube?
-Negative pressure in the middle ear causing tympanic retraction
What is the epitympanic recess?
-Upper portion of middle ear where auditory ossicles are
Name the two muscles of the middle ear, their innervation, and what they are attached to
- Tensor typani -> CNV -> malleous
- Stapedius -> CNVII -> Stapes
What is the function of the muscles in the middle ear?
-Damper sounds to protect against loud noise
Name the components of the external ear
- Pinna -> helix, antihelix, concha, tragus, antitragus and lobule
- External auditory canal
- Tympanic membrane
What is the function of the eustachian tube?
-Ventilation of the middle ear to maintain pressure between back of nose and outside
Why are children prone to middle ear infections?
-Eustachian tube is shorter, narrower and more horizontal so doesn’t aerate as much
What is a tympanic retraction?
-When the tympanic membrane becomes sucked into the middle ear due to negative pressure in the middle ear
What is acute otitis media?
-Acute infection of the middle ear
What is glue ear?
-Acute otitis media with effusion -> effusion accumulates behind the tympanic membrane as a result of prolonged negative pressure causing conductive hearing loss
What are grommets?
-Ventilation tubes inserted into the tympanic membrane when the eustachian tube fails to function adequately
Name 3 bacteria genus which can cause acute otitis media
- Pneumococcus
- Haemophilus
- Streptococcus
Name 3 common complications of acute otitis media
- Perforation
- Chronic infection
- CNVII palsy
What is mastoiditis? Why can it be serious?
- Inflamation and infection of the mastoid air cells due to pus causing back pressure into the mastoid cavity
- Can lead to intracranial infection and death
How do you recognise mastoiditis?
-Uneven ears and obliteration of ear crease
What is a cholesteatoma?
-Accumulation of dead skin cells leading to a necrotic mass of dead cells which can cause erosion of the middle ear and bones due to release of lytic enzymes
Why can middle ear infection lead to bell’s palsy?
-CNVII runs through internal auditory meatus into middle ear. Infection can cause inflammation of CNVII leading to bells palsy
Why can middle ear infection lead to loss of taste?
-Chorda tympani is a branch of facial nerve supplies special sensory innervation to anterior 2/3 of tongue and joins facial nerve via the middle ear. Infection can lead to inflammation/damage to chorda tympani resulting in loss of taste signals being sent to the brain
What makes up the vastibular labyrinth of the inner ear?
-3 semicircular canals and 2 sacs (utricle and saccule)
How does the vestibular labyrinth contribute to balance?
- All components are joined together and fluid filled
- Utricle and saccule have cuppula -> areas of gelatinous matrix with stereocilia inside -> during movement fluid in the semicircular canals moves-> moves the sterocilia in the matrix which provides moving sensation
In which directions do utricle and saccule sense movement?
- Utricle -> up and down
- Saccule-> back and forward
What things contribute to balance?
-Vestibular labyrinth, balance and sensation
What is benign positional paroxysmal vertigo?
- Disorder of the inner ear leading to repeated episodes of positional vertigo which lasts a few seconds
- Normally due to otolith
What is meniere’s disease?
-Vertigo, hearing loss, tinnitus and aural fullness caused by excess fluid in the inner ear (endolympatic hydrops)
How does the cochlea of the inner ear allow hearing?
- Stapes transmits vibrations to middle ear via oval window
- Vibration of perilymph in scala vestibuli and scala tympani
- Vibrations are converted to electrical signals which send action potentials to the brain
