Ears Flashcards
What are the components of the pinna?
Tragus & antitragus Triangular fossa Helix & antihelix Concha Lobule
Give some examples of congenital pinna deformities.
Antihelix deformity
Microfia = pinna malformation (can replace with cartilage from ribs/other ear)
Pre-auricular pit
Pre-auricular skin tag
Give some examples of acquired pinna deformities.
Trauma to elastic cartilage (note: 0% of ear damaged)
Pinna haematoma = trauma causes haematoma between cartilage and perichondrium —> hypoxia (perichondrium not in contact with cartilage) —> pressure necrosis —> “cauliflower ear” (fibrosis, pale, shrivelled outer ear)
What are the features of the external acoustic meatus?
Sigmoid, ~ 2.5cm long (therefore in order to visualise the tympanic membrane, pull the pinna to straighten the canal)
Lateral 1/3 = cartilaginous extensions of auricular cartilages (wider)
Medial 2/3 = bony tunnel through temporal bone (narrower)
Lined by skin, hair, modified sweat glands (produce cerumen)
Innervated by auriculotemporal nerve (branch of CNV3 - mandibular nerve) and auricular branch of vagus nerve (CNX)
What is earwax composed of? What is the function of earwax? What clinical conditions can be caused by earwax? ….
Earwax = cerumen + dead epithelial cells
- protects skin of ear
- cleans & lubricates external ear
- protection from water and microorganisms
- foreign bodies compacting earwax
- otitis externa = inflammation of the outer ear and external acoustic meatus —> earache
…..
What is the function of the tympanic membrane? What are the components of the tympanic membrane?
Connected to the malleus in order to transmit sound by vibration
Epithelium —> Collagen —> Mucous membrane
- only malleus visible through the membrane
- loose part of membrane superior to malleus —> pars flaccida (haphazard irregular collagen)
- taut rest of membrane —> pars tensa (regular radial collagen)
- light reflex is normal inferior to malleus (points at patient’s feet in right ear)
Give some examples of tympanic membrane-related diseases and conditions.
Tympanosclerosis = dense, white plaques present + bulging membrane (pus/fluid in middle ear)
“injection of drum” —> membrane becomes dull or red or yellow with dilated blood vessels
Retraction of membrane due to negative pressure in the middle and inner ear (caused by Eustachian tube dysfunction):
- pars flaccida first to pull inwards
- diffuse light reflex
- incus & stapes visible
- sound not conducted correctly
Cholesteatoma = necrotic mass of dead skin accumulating in retraction pocket of tympanic membrane —> production of lytic enzymes —> erosion of middle ear structures & bone —> hearing loss
Perforation:
- trauma/otitis media (pressure necrosis)
- usually heal spontaneously unless the rupture is large
What are the components of the middle ear?
Tympanic cavity (immediately adjacent to tympanic membrane) Epitympanic recess (superior) Ossicles (synovial joints): malleus, incus, stapes Oval window (medial to foot of stapes)
Communicates with:
- Anterior: nasopharynx via Eustachian tube/pharyngotympanic/auditory tube
- Posterior: mastoid area
What are the contents of the tympanic cavity?
- oval window —> stapes
- mastoid antrum contains mastoid cells (air-filled spaces)
- chorda tympani nerve (branch of CNVII)
- round window (allows movement of fluid within inner ear)
- tympanic branch of glossophayrngeal nerve (CNIX)
- Eustachian/pharyngotympanic tube
- branch from carotid plexus
- tensor tympani
What is otitis media?
Bacterial/viral infection of the middle ear cavity
Causative organisms: pneumococcus, Strep., Haemophilus (nasal bacteria)
Acute:
- painful, bulging, red ear drum with pus in middle ear
- occasionally causes perforation & discharge
- usually heals itself
With effusion (“glue ear”):
- thick effusion accumulates behind ear drum (exudate not absorbed)
- prevents aeration to equilibrate pressure (secondary to prolonged negative pressure) —> retracted tympanic membrane & conductive hearing loss
Complications:
Acute suppuration and back pressure into the mastoid cavity (mucous membrane continuous; pus fills mastoid air cells —> loss of reservoir for rapid aeration of the ear)
—> mastoiditis
—> protruding mastoid causes loss of crease behind ear
—> intracranial infection (meningitis, cerebral abscesses)
What are the features of the Eustachian tube?
Eustachian tube/pharyngotympanic tube/auditory tube
Lateral 1/3 = bony
Medial 2/3 = cartilaginous (adult)
- usually closed; intermittently pulled open by palate muscles whilst swallowing
- children: tube shorter and more horizontal (therefore more prone to otitis media from infections of nasal cavity)
What is mastoiditis?
Presence of air-filled spaces provide ideal medium for infection
Infection can spread to bone —> osteomyelitis —> middle cranial fossa —> breach of cranial vault —> meningitis
Drainage of pus required (avoid facial nerve)
What is the purpose of the air-filled spaces in the mastoid antrum?
- helps equilibrate pressure of tympanic cavity with pressure outside of ear
- storage of oxygenated air
What are the ossicles? What muscles are present and what function do they serve?
Ossicles: form osseous chain, 90 degrees to each other to transmit sound, develop from branchial arches
- MALLEUS = articulates with tympanic membrane, incus, & tensor tympani
- INCUS = no muscle attachment, articulates with malleus and stapes
- STAPES = articulates with stapedius, incus, and oval window (opening into cochlea)
Tensor tympani = contracts to pull handle of malleus medially, slowing sound (supplied by CNV3 - mandibular nerve)
Stapedius (origin is pyramidal entrance) = contracts to pull stapes posteriorly, preventing excessive oscillation which would damage the cochlea
These muscles are sound absorbers - prevent pressurisation causing pain from loud sounds
What are the components of the internal ear? What is the function of these components?
Cochlea = hearing
Vestibular labyrinth = balance
(interplay between vestibular end organ, vision, & sensation)
- 2 fluid-filled sacs: utricle & saccule (one for up-down acceleration, one for forwards-backwards acceleration)
- 3 fluid-filled cylinders: information on orientation due to movement of fluid over organelles
