The Ear Flashcards
Describe the external ear cavity. (4)
The pinna, external auditory meatus, ear canal and lateral surface of the tympanic membrane.
Describe the middle ear cavity. (5)
The ossicles (malleus, incus and stapes), the Eustachian tube and the medial surface of the tympanic membrane.
Describe the inner ear cavity. (3)
The cochlear and vestibular apparatus (vestibule and semicircular canals).
Describe the nerves that carry general sensation to the ear. (5)
C2/C3 spinal Vagus Trigeminal (auriculotemporal nerve) Glossopharyngeal (tympanic nerve) (Small bit of facial).
List some common signs and symptoms of ear pathology. (6)
Otalgia, discharge, hearing loss (conductive or sensorineural), tinnitus, vertigo, facial nerve palsy.
Explain how otalgia can be a sign of non-ear pathology. (4)
Can be a sign of referred pain from larynx, pharynx or TMJ.
They share innervation with one of the nerves that supplies general sensory to the ear, so it refers the pain there.
What is the purpose of the external ear? (1)
Collect and focus sound waves onto the tympanic membrane.
Describe 4 pinna abnormalities.
Facial nerve palsy - can cause shingles f the facial nerve in Ramsay Hunt Syndrome.
Chondritis
Pinna haematoma - blunt constant to pinna leads to haematoma between avascular cartilage and vascular perichondrium.
Cauliflower deformity
Describe the external acoustic meatus. (4)
Lined with keratinised stratified squamous epithelium that continues onto the lateral surface of the tympanic membrane.
Cartilaginous outer 1/3 and bony inner 2/3 (through temporal bone) in a sigmoid shape, so pull the pinna up and out to visualise tympanic membrane.
Describe otitis external. (4)
Infection of the external ear meaning tympanic membrane invisible.
Often pseudomonas or staph.
Presents with pain hearing loss and discharge.
Treated with abx.
Apart from otitis externa, describe 3 pathologies of the outer ear.
Was build up
Perforation of the tympanic membrane
Bulging tympanic membrane secondary to otitis media.
Describe the middle ear cavity. (6)
Air filled cavity containing ossicles connected by synovial joints. Vibrations of sound on tympanic membrane > malleus > incus > stapes > oval window of the cochlear.
Describe the stapedius muscle. (3)
Acts to dampen the movement of the stapes on the oval window to stop damage, called the protective acoustic reflex.
Innervated by the facial nerve, so facial nerve palsy gives hyperacusis.
Describe the Eustachian tube. (3)
It is a tube that connects the middle ear to the nasopharyngeal that acts to equilibreate the pressure difference that occurs when the mucus membranes of the middle ear reabsorb air.
Explain why babies can pass infections of the nasopharynx to the middle ear. (1)
The Eustachian tube of babies is much shorter and more horizontal, meaning that infection is more likely to spread.
Describe otosclerosis. (4)
A disease of unknown cause that causes fusion of the ossicles that is the leading cause of gradual onset conductive hearing loss in the young.
Describe cholesteatoma (4)
A sac of trapped epithelial cells that proliferate and erode through bone, often secondary to Eustachian tube dysfunction. Not malignant, painless, often smelly otorrhoea.
Describe glue ear. (6)
Otitis media with effusion
A build up of fluid and negative pressure in the middle ear due to Eustachian tube dysfunction. Can resolve on its own, can need grommets. Tympanic membrane is straw coloured and retracted.
Explain how grommets can help in glue ear. (2)
They act to equilibriate the pressure between the atmosphere and the middle ear. They do not drain the fluid.
Describe acute otitis media and it’s complications. (8)
An acute middle ear infection commonly in children associated with strep throat (strep pneumoniae).
Presents with otalgia, infective symptoms, red tympanic membrane with possible bulging.
Complications include perforation, facial nerve involvement, mastoiditis, intracranial complications (meningitis, sigmoid sinus thrombosis, brain abscess).
Describe mastoiditis. (3)
An infection of the mastoid air cells that has spread via the mastoid antrum from the middle ear.
Describe the cochlea. (4)
Vibration is detected by the displacement of fluid in the tubes from the oval window into the round window. This moves stereocilia which generates an action potential in the vestibulocochlear nerve.
Describe the vestibular apparatus. (6)
It includes the 3 semi-circular ducts (one in each plane), the saccule and the utricle, which are fluid filled sacs containing stereocilia which bend as the head moves position. This generates and action potential in the vestibulocochlear nerve, which helps us to perceive and maintain balance.
Describe benign paroxysmal positional vertigo. (4)
Most common cause of vertigo. Comes in second long spurts resulting from moving the head because crystals have formed in the semicircular canals which dislodge on movement, but continue to form ripples after movement ceases. Hearing unaffected.
