Anatomy and physiology of hearing Flashcards
3 main divisions of the ear and how you look in the ear
external, middle and inner
otoscope, microscope and speculum
pinna/auricle
Visible part of the ear from the outside
Name the outer visible parts of the ear
helix, triangular area, antihelix, lobule, tragus, concha, meatus and antitragus
Skin epithelium
stratified keratinised epithelium
What underlies the skin to give the pinna its structure?
elastic cartilage
External ear canal length
4cm long in adult
Lateral 1/3 of ear
cartilage and skin with ceruminous and sebaceous glands
Hair changes through the ear
thick on outside and finer inside
Hair purpose in ear
disinfectant and barrier
Medial 1/3 of ear
no hairs, cilia or wax
made of skin and bone
Where does skin grow from in the ear?
umbo in the tympanic membrane outwards
Where is the skin in ear shed?
lateral 1/3 and trapped in wax
Pinna haematoma
rugby ear
trauma separates cartilage and tears blood vessels
Outer, middle and inner layers of tympanic membrane
continuous with skin of EAC
fibrous layer
respiratory epithelium
dimensions of the tympanic membrane
1cm in diameter, 1/10 mm thick
ossicles part
head of malleus, incus and stapes
What is the clinical condition related to the respiratory epithelium of the middle ear?
glue ear due to mucous
How is the middle ear connected to a) mastoid system and b) nasopharynx
a) aditus
b) Eustachian tube
purpose of middle ear
conduct sound from tympanic membrane to the inner ear - SOUND CONDUCTION
How can the middle ear be disrupted?
otosclerosis or trauma
contents of the middle ear - nerve
facial nerve –> chorda tympani
most important relations of the middle ear
middle cranial fossa, internal carotid artery, sigmoid sinus + internal jugular vein
how many segments of the facial nerve?
6
Which facial nerve segment has a fallopian tube which is 10% dehiscent?
tympanic
Where does the facial nerve exit through the skull?
stylomastoid foramen
What does the facial nerve supply?
motor supply of muscles of facial expression
taste anterior 2/3 tongue from chorda tympani
Anatomical relations - complications of otitis media and cholesteatoma
meninges, middle cranial fossa, facial nerve, mastoid cavity, inner ear and sigmoid sinus/IJV
What is cholesteatoma?
skin in wrong place - keratinised squamous epithelium in middle ear
Cholesteatoma congenital or acquired?
both
Inner ear parts
bony and membranous labyrinth
cochlear
peripheral vestibular apparatus
vestibulocochlear nerve
Membranous labyrinth fluid
perilymph and endolymph
hearing organ and balance organ
cochlear
peripheral vestibular apparatus
Parts of peripheral vestibular apparatus
utricle, saccule and semicircular canal
Briefly describe hearing
middle ear vibration –> nerve impulses
foot of stapes vibrates in oval window
pressure wave through fluid in cochlear
detected by hair cells in organ of corti
transmitted by brainstem by vestibulocochlear nerve
Explain the importance of each part of the peripheral vestibular apparatus in balance
semi circular canals - head rotation
saccule - vertical plane
utricle - horizontal plane
sensation to middle ear nerve
jacobsons nerve - glossopharyngeal tympanic branch
sensation to posterior half of EAC nerve
Arnold’s nerve - auricular branch of vagus nerve
anterior half of EAC sensation nerve
facial nerve
pinna nerve supply
CN V3
Why is shared innervation of the nerve supply important?
otalgia worrying if no ear cause
head and neck cancer
