6) The Ear Flashcards by Lauren Croft

The ear is divided into which 3 parts?

External ear
Middle ear
Internal ear

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What separates the external and middle ear?

Tympanic membrane

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Which tube joins the middle ear to the nasopharynx?

Pharyngotympanic/Eustachian/Auditory tube

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What is the external ear comprised of?

Auricle (Pinna) - elastic cartilage covered by skin

External acoustic meatus

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What structures comprise the auricle (pinna)?

Helix (outer rim)
Tragus (flap guarding external acoustic meatus)
Non-cartilaginous lobule (lobe)

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What is the blood supply to the external ear?

Posterior Auricular & Superficial Temporal arteries (ECA)

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Which nerves provide sensory innervation to the auricle?

Anterior to the external auditory meatus - Auriculotemporal nerve (branch of mandibular Viii)
Rest of auricle - Great Auricular nerve

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What is the external auditory meatus?

Cartilaginous tube/canal lateral 1/3
Bony canal medial 2/3
Lies in temporal bone
Lined by skin secreting cerumen (modified sebum)
Sigmoid shaped

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What is ear wax comprised of?

Discarded skin cells & cerumen of external auditory meatus

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What is the tympanic membrane?

Partition between external & middle ear
Shallow cone, apex points medially
Thin, oval, semi-transparent, pearly-grey membrane

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Which nerves supply the tympanic membrane?

External surface: Auriculotemporal nerve (branch of Viii)
Auricular branch of vagus nerve

Internal surface: Glossopharyngeal nerve

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What is the Ear-Cough reflex?

Stimulation of Auricular branch of Vagus
e.g. insertion of cotton bud
Produces cough reflex, some even vomit
Over-sensitivity

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How can the tympanic membrane be affected in disease?

Dull & becomes red/yellow
Dilated blood vessels - injection of drum
Dense, white plaques - Tympanosclerosis
Bulging - Pus/fluid in middle ear
Retracted - Infratympanic cavity pressure reduced, obstruction of Eustachian tube
Perforation - Trauma, Infection

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What makes up the middle ear?

Narrow air-filled chamber in petrous part of temporal bone
Tympanic cavity proper
Epitympanic recess

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What is the tympanic membrane proper?

Space directly internal to tympanic membrane

Connected to nasopharynx & mastoid air cells

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What is the epitympanic recess?

Space superior to the tympanic membrane

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Is the Auditory tube usually open or closed?

Closed

Intermittently opened by pull of attached palate muscles when swallowing

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What are the contents of the middle ear?

Auditory ossicles: Malleus, Incus, Stapes
Stapedius & Tensor Tympani muscles
Chorda Tympani nerve
Tympanic plexus of nerves

What are the auditory ossicles?

Malleus
Incus
Stapes

What is the function of the auditory ossicles?

Relay vibrations encountered by tympanic membrane to inner ear
Amplify & concentrate sound energy to oval window

What is the function of the tensor tympani muscle?

Inserts into handle of malleus, pulls handle medially
Tenses tympanic membrane, reducing amplitude of oscillations
Prevents damage to inner ear when exposed to loud sounds

What is the function of the stapedius muscle?

Pulls stapes posteriorly, tilts its base over oval window
Tightens anular ligament, reduces oscillatory range
Prevents excessive movement of stapes
Innervated by nerve to stapedius (facial)

What is the relationship of the facial nerve and the middle ear?

CN VII lies in the facial canal
separated from tympanic cavity by thin bony partition

Middle ear infection may cause lesion

What is the inner ear?

Labyrinth
Channels hollowed out of the Petrous temporal bone,
surrounding the membranous labyrinth

Which structures are contained within the middle ear?

``` Vestibule Semi-circular ducts & canals Cochlea Cochlear duct Organ of Corti ```

What are the main functions of the inner ear?

Receptors that respond to rotational acceleration & static pull of gravity Receptors of auditory apparatus

What is an auricular haematoma?

Trauma resulting in bleeding within auricle Blood collects between perichondrium & auricular cartilage Distorts contours of auricle If blood not aspirated - fibrosis (Cauliflower's ear)

What congenital pinna deformities can occur?

Antihelix deformity Pinna malformation Pre-auricular pit Pre-auricular skin tag

What is acute otitis externa?

Infection/inflammation of the external acoustic meatus Common in swimmers Itching & pain in external ear

What is otitis media?

Infection of the middle ear Often secondary to URTIs via Eustachian tube More common in children - shorter, more horizontal eustachian tube Earache, bulging red tympanic membrane (pus/fluid) Inflammation of mucous membrane may cause blockage of eustachian tube

Name some causes of a perforated tympanic membrane

Otitis media, insertion of foreign bodies, trauma, excessive pressure (scuba diving) Middle ear deafness, often heal spontaneously

What is mastoiditis?

Infection of mastoid antrum & mastoid air cells Results from otitis media - inflammation of mastoid process (swelling behind ear) - may spread into middle cranial fossa in children (osteomyelitis)

How might the Eustachian tube be blocked?

Swelling of mucous membrane e.g. infections Low pressure in tympanic cavity, retraction of tympanic membrane Hearing affected Adenoidal hypertrophy (children, EBV)

What is hyperacusis?

Loss of protective action against loud noises | e.g. lesion of facial nerve, paralysis of stapedius

How does motion sickness occur?

Discordance between vestibular & visual stimulation

What 3 symptoms do injuries of the peripheral auditory system cause?

Hearing loss Vertigo Tinnitus

How does conductive hearing loss occur?

Anything in external or middle ear that interferes with conduction of sound or movement of oval or round windows People will speak with a soft voice Surgery/hearing device

How does sensorineural hearing loss occur?

Defects in pathway from cochlea to brain cochlea, cochlea nerve, brainstem Cochlear implants

What is Ménière syndrome?

Blockage of cochlear aqueduct Recurrent tinnitus, hearing loss & vertigo Sense of pressure in ear, distortion of sounds & sensitivity to noise

What is cholesteatoma?

Necrotic mass of dead skin caused by: Blockage of eustachian tube Negative middle ear pressure leads to retraction pockets Dead skin cells accumulate Erosion of middle ear structures & bone via lytic enzymes

What is otalgia?

Ear pain Infection/Inflammation around ear Pain from teeth, pharynx or cervical spine commonly referred to the ear

What is pruritus?

Itching | Primary disorder of external ear, or middle ear discharge

What is otorrhoea?

Discharge from the ear Indicates acute or chronic infection Blood/CSF discharge associated with skull fracture