Week 1 Flashcards
Peripheral auditory system
Outer ear
Middle ear
Inner ear (cochlea and vestibular system)
Auditory nerve
Major landmarks of auricle/pinna
Helix
Lobule/lobe
Concha
Helix
Curled margin marking outermost borders (cartilage covered by skin)
Concha
Entrance to EAM
Functions of Pinna
Receives and enhances sound waves
Aids in sound localization, but both sides required
Outer ear: external auditory meatus (EAM)
7 mm in diameter
2.5 cm long
Lateral /anterior third is made of cartilage (has cerumen glands)
Major contributor to resonance and amplification
External ear amplify sounds by 20 to 25 dB
How and why the EAM amplifies sound?
Serves as a quarter wave resonator (filters out sound waves)
The cerumen coating and cartilage help it minimize sound absorption
Outer ear: tympanic membrane
Structure-middle/core layer (made of radial fibroelastic connective tissue that provides optimal strength and tension
Major landmarks of tympanic membrane?
Umbo
Cone of light
Vibratory characteristics of tympanic membrane
Vibrates in responses to changes in air pressure
Different parts vibrate at different frequencies
Tenor tympani
Alter tension of the TM to increase frequency of vibration
Places that amplify traveling signals in outer and middle ear:
Pinna
EAM
Ossicles
Cochlea
Middle ear
Air filled chamber within temporal bone
Begins at tympanic membrane and ends at oval window
Houses the ossicles (malleus, incus, stapes)
Has two small muscles
Tenor tympani
Stapedius
Middle ear: auditory ossicles
Malleus
Incus
Stapes
Malleus
Connects to the tympanic membrane
Consist of head, neck, anterior and lateral processes and manubrium
Incus
Articulate with malleus through incudo-malleolar joint
Articulates with stapes through incudo-stapedial joint
Consist of body, short process, and long process
Stapes
Consist of the head, legs, and foot plate
Foot plate connects onto the oval window of the cochlea
Eustachian tube
Runs from middle ear to nasopharynx
Opening is lateral to the adenoids
Tensor Veli palatini connects laterally to it
Function of Eustachian tube:
Ventilates middle ear
Equalize pressure around tympanum
Permit drainage of middle ear fluid into nasopharynx
Stapedius muscle
6mm long
Originates on the posterior wall of the middle ear and inserts itself onto the head of the stapes
When contracted it pulls the stapes posteriorly and laterally to deflect the pressure from the oval window
In return, it stiffens the ossicular chain and the tympanic membrane
Reflex is triggered around 80 dB +
It reduces sound by 10 dB
Dampening
As sound travels, its energy gradually decreases
To prevent dampening, the following help amplify the signal:
Pinna
EAM
Ossicles
Cochlea
