The Ear

Question 1

Describe the structure and function of the external ear

Answer 1

Auricle
External auditory canal
Pinna - helix, triangular fossa, antihelix, concha, crus of helix, tragus, anti tragus, external auditory meatus, lobule
Transmit sound waves from environment to middle ear

Question 2

Describe the structure and function of the middle ear

Answer 2

Tympanic membrane - pars flaccida, lateral process of malleus, handle of malleus, umbo, light reflex, pars tensa
Ossicles - malleus, incus, stapes (vibrate with sound waves)
Muscles - tensor tympani, stapedius (dampens loud noises)
Eustachian tube (equalises pressure)
Mastoid air cells
Sound waves –> kinetic energy. Sound is transmitted via the ossicles to the oval window.
Connection between environment and inner ear

Question 3

Describe the structure and function of the inner ear

Answer 3

Cochlea - converts sound pressure patterns into electrochemical impulses which are passed onto the brain via the auditory nerve
Vestibular labyrinth - contributes to balance
When the stapes presses on the oval window it causes the perilymph (liquid of the inner ear) to move

Question 4

Describe some cases of common disorders and pathologies affecting the external ear

Answer 4

Congenital pinna deformities 
Pinna haematoma (cauliflower ear) - haematoma between cartilage and perichondrium prevents oxygenation --> necrosis  
Otitis externa 
Foreign body
Wax

Question 5

Describe some cases of common disorders and pathologies affecting the middle ear

Answer 5

Tympanic membrane perforation
Otitis media
Otitis media with effusion (glue ear) which can lead to mastoiditis –> intracranial infection –> death, and facial nerve dysfunction
Cholesteatoma - negative pressure –> retraction pockets –> accumulation of dead skin cells and debris –> necrotic mass –> erosion of middle ear structures and bones by lytic enzymes
Often treat with grommets

Question 6

Describe some cases of common disorders and pathologies affecting the inner ear

Answer 6

Cochlear disease:
Sensorineural hearing loss, tinnitus
Vestibular disease:
True rotational vertigo, labyrinthitis –> vertigo

Question 7

Describe the anatomy of the temporal bone

Answer 7

Six parts - squamous, mastoid, tympanic, styloid process, zygomatic, petrous

Question 8

Describe the nerve supply to the pinna, external auditory meatus, tympanic membrane and middle ear

Answer 8

External ear - greater auricular (cervical), lesser occipital, auricular branch of vagus, auriculotemporal
Tympanic membrane - auriculotemporal (V3), auricular (X), facial (VII), glossopharyngeal (IX)