ENT Flashcards
what is the function of the the auditory ossicles?
transfer and amplify air vibrations into the inner ear to be processed as sound
what is external acoustic meatus?
ear canal - starts from outer ear (conchae) and extends to middle ear
tympanic membrane anatomical features?
lateral process of malleus
pars flaccida
pars tensa
cone of light
what are abnormal TM signs?
Perforations
Tympanosclerosis - deposits of dense hyaline tissue on the middle ear mucous membrane
Red and bulging membrane
Retraction of the membrane
what is microtia?
underdeveloped outer ear cartilage
what is acoustic neuroma and signs of acoustic neuroma?
non-cancerous tumour which compresses against the vestibular nerve (CN VIII)
vertigo
hearing loss
tinnitus
absent corneal reflex (cotton wool)
these symptoms occur due to pressure symptoms on CN VIII
structure of ear?
outer - pinna and ear canal (external acoustic meatus)
middle - tiny ossicles (stapes, incus, malleus)
inner - cochlea (converts sound waves into electrical impulses)
semicircular canals - resp for balance
What is the structure and function of the external ear?
pinna/auricle - cartilaginous structure to support external ear
pinna function: directs sound waves towards opening of EAM
lobule - unknown function
EAM (Ear canal) - short curved tube that burrows through temporal bone, ends at TM
extrenal ear function: collects sound waves and channels them into the ear canal (external auditory meatus), where the sound is amplified. soundwaves travel to TM
Describe the structure of the ear canal?
hair follicles - forms protective barrier w ear wax, stops foreign bodies from entering ear
ceruminous glands - make cerumen (ear wax) - prevent foreign objects from damaging the TM
Describe the structure and function of TM
thin membrane which separates external ear from middle ear
shaped like cone, protruding into middle ear
Describe the physiology of hearing
when sound waves reach the eardrum it vibrates and transmits the vibrations into ossicles of middle ear
Describe the structure and function of the middle ear
air-filled cavity within the temporal bone
lateral wall: eardrum
internal (medial) wall: separates middle from inner ear
posterior wall: opening called mastoid antrum - connects middle ear w mastoid cavity within the temporal bone
roof: called epitympanic recess
anterior wall: opening for eustachian tube - connects middle ear to nasopharynx
What is the function of the oval window?
thin membrane opening from middle ear to cochlear (inner ear)
3 functions of Eustachian tube?
- equalising pressure across TM
- protecting middle ear from reflux of fluid from nasopharynx
- clears out middle ear secretions
How are sound vibrations transferred from eardrum to ossicles?
sound enters via outer ear → eardrum vibrates → handle of malleus rests on eardrum → base of stapes rests on oval window → oval window transmits vibrations to inner ear
so the order of vibration is as follows:
eardrum → malleus → incus → stapes → oval window → transfers vibrations to INNER EAR
What are the 2 components of the labyrinth?
bony labyrinth: tough bony shell filled with perilymph
membranous labyrinth: inside bony labyrinth, filled with endolymph
the movement of perilymph & endolymph plays role in hearing & balance
what are the 3 parts of the inner ear?
vestibule: central part of bony labyrinth
cochlea: fluid-filled, spiral-shaped cavity, plays role in hearing & auditory transduction
semicircular canals: 3 tiny fluid-filled tubes that help with balance
Describe the 3 structures of the cochlea?
scala vestibuli - connects to middle ear via oval window - PERILYMPH
cochlear duct - houses organ of Corti - contains hearing receptors/hair cells - ENDOLYMPH
scala tympani - connected to middle ear via round window - PERILYMPH
How does the organ of Corti transmit sound to the brain?
sound travels through external ear & ossicles of middle ear → when foot of stapes beats against the oval window → it transfers vibration to perilymph inside scala vestibuli → this forces the fluid into motion → this transmits to organ of Corti inside cochlear duct → hair receptors in cochlea convert these vibrations into an electrical impulse → this sent to auditory cortex via CN VIII
Describe the 2 components of the apparatus of the inner ear?
responsible for balance
semicircular canals + 2 otolith organs
What are the semicircular canals and otolith organs?
3 semicircular canals - perpendicular to each other - contain endolymph - opens into utricle
canal opens into ampulla - detect changes in head rotation - dynamic eqm
endolymph inside canals moves when head moves → hair cells fire electrical signal → signal detected by vestibular branch of CN VIII
What are the otolith organs?
otolith organs: utricle & saccule - ENDOLYMPH - contains macule - contains balance receptor - detect changes in static eqm - detect head position in relation to gravity
what is csf rhinorrhea halo sign from ear?
this is CSF - if this leaks from ear then indicates basal skull fracture
what is ear discharge associated with?
usually middle ear infection
