Lecture 13- The external ear Flashcards
the pinna
cartilaginous covered with skin and fatty tissue
how long is the external auditory meatus
2.5cm- ends at the lateral surface of the TM
function of external ear
Collects, transmits and focuses sound waves onto the tympanic membrane causing the tympanic membrane to vibrate
Pinna (auricle) abnormalities
- Congenital
- Inflammatory
- Infective
- Traumatic
infective causes of pinna abnormalities
ramsey hunt syndrome
perichondritis
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E.g. Ramsey hunt syndrome
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Unilateral face droop and red ear with vesicles
- Perichondritis
- Layer which coats the cartilage and provides blood supply
- Causes by infection introduced by ear piercings/ insect bites
- Needs ABx
traumatic cuase of pinna abnormality
pinna haematoma
pinna haematoma
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Pinna haematoma- accumulation of blood between the cartilage and its overlying perichondrium from blunt injury
- Common in contact sport
- Subperichondrial haematoma deprive cartilage of blood supply, increase in blood build up = increased pressure= necrosis of tissue
treatment of pinna haematoma
- Drainage and prevent re-accumulation/re-apposition of two layers
- Untreated fibrosis, new asymmetrical cartilage development cauliflower deformity)
shape of the external acoustic meatus
sigmoid shape
EAM lined with
- Lined with keratinising, stratified squamous epithelium continuous onto lateral surface of tympanic membrane
embryology of EAM
from cleft of the 1st and second pharyngeal arches lined with ectoderm
make up of the EAM
- Cartilaginous outer 1/3
- Hair
- Sebaceous
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Ceruminous glands (wax glands lined cartilage part)
- Barrier for foreign objects
- And bony inner 2/3 (petrous bone)
special function of EAM
self cleaning
how is the eam self cleaning
- Epithelial migration
- Surface of the skin moves laterally from the tympanic membrane towards the ear canal
nromal typanic membrane features when using otoscope
- Corn of light (light reflex)–> how light reflects off tympanic membrane off the otoscope
- Large extent of tympanic membrane = pars tensa and par flaccida
- Can see attachment of the manubrium of the malleus
Common condition involving external acoustic meatus
- wax/ foreign body
- otitis externa
Otitis externa
Inflammation of the external ear esp EAM
- Known as swimmer ear
presentation of otitis externa
- Presents with ear pain and itchiness
- Discharge
- Rare complication of otitis externa=
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malignant otitis externa
- Rare and very serious–> potential life threatening esp in immunocompromised e.g. diabetics
Tympanic membrane common abnormalities
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Disease can affect the tympanic membrane itself
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- E.g. tympanosclerosis
- Scarring other tympanic membrane
Tympanic membrane common abnormalities
Can also be affected by disease happening in the middle ear e.g.
acute otitis media
acute otitis media
- Building secondary to bacterial acute otitis media
- Infections usually viral
- Acute otitis media with effusion (glue ear)
- Underlying problem is not infection
- Causes the tympanic membrane to become retracted –> sucked into the middle ear cavity
- Increasing negative air pressure
- dysfucntion of the eustachian tube –> meaning liquid is not replaced when the mucus membrane absorbed air–> equilibrium lost–> negative air pressure
- reduced TM movement- reduced ossicle meovemnt -> decreased hearing
- May see presence of fluid within middle ear via air bubbles
why does acute otitis media predisopose to acute ear infections
- by nature of shorter and more horizontal ET
- stagnant liquid
- another TM dysfunction- Cholesteatoma
- Cholesteatoma
- Rare- should not be missed
- Not a tumour or related to cholesterol
- If chronically increased negative ear pressure in the middle ear – the pars flaccida will start to retract forms a sac/pocket
- Trapping stratified squamous epithelium and keratin collecting in the retraction pocket
- Proliferates forming cholesteatoma
cholesteatoma usually secondary to
secondary to chronic eustachian tube (ET) dysfunction
- Symptoms of cholesteatoma:
painless, often smelly otorrhea (ear discharge) +/- hearing loss
cholesteatoma is potentially serious… why
- not malignant but slowly grows and expands
- Can erode ossicles, mastoid/petrous bone, cochlea via enzymatic action
outline how a cholesteotoma is formed
- eardrum is sucked inwards due to negative pressure caused by blockage of ET
- early cholesteatoma cyst forms in the small pocked - skin cells collect
- cholesteatoma grows- at first it is more liekly frow into (erode) and destroy structures in the middle iear
- in time may grow and erose into and damage structures in the inner ear or even erode into the bone fo the enarby skull and into the brain
