Speech Mech Chapter 9 Part 1 Flashcards
Audition
The process associated with hearing
The ear is
an energy transducer; it changes acoustic energy into electrochemical energy
Structures of the ear
Outer, middle, inner ear, auditory pathways
The pinna (auricle)
Prominence referred to
“the ear”
Structure provided
by a cartilaginous framework
A Collector of sound that is processed in the middle ear and cochlea
Landmarks of pinna
•Helix (curled margin) and auricular tubercle (posterior bulge on the helix)
•Concha- entrance to ear canal
Concha: aids in
localizing the sound sources that come from the front, below and above the head
Concha helps
to funnel sounds directed to it to the external auditory canal
The auricle is more efficient at delivering
high frequency sounds than low frequency
The auricle helps
in localization of sounds delivered to the head
Microtia
small auricle
Anotia
refers to complete absence of the pinna
Pre-auricular tags
are prominences that form prenatally anterior to the pinna
External auditory meatus (EAM) is the
External ear canal
and is 7 mm in diameter and 2.5 cm long
External auditory meatus (EAM)Terminates at the
tympanic membrane
* Two-thirds of ear canal housed in bone (osseous
portion)
* One-third of ear canal composed of cartilaginous
parts
Resonating cavity that contributes to hearing
Determine resonant frequency
Outer third- line with hair cells and cerum (ear
wax)
protects by trapping dirt and insects
The two portions of the EAC meet
together at the
osseocartilaginous
junction
The condyle lies just below this junction
and when the mandible (jawbone)
overrides
its normal position, the
condyle will press into the junction
causing pain
Referred to as TMJ or Temporomandibular Joint
disorder
Produces a referred pain in the ear referred to as
otalgia (ear pain)
Otitis externa
refers to
inflammation of the skin of the
external ear.
Cerumen
(ear wax) impaction
meatal atresia
absence of the
external auditory meatus
Tympanic Membrane (TM) Also known as the
eardrum
Tympanic Membrane Separates
the middle ear from the
outer ear
Tympanic Membrane is
Oval shaped, 10 mm in diameter
* Thin three layered sheets of tissue
* Landmarks
Umbo
point of attachment for malleus,
middle ear bone- location is cone of light
(reflects light from otoscope)
The TM marks the border between the
outer and middle ear
Constructed of 3 layers
outer middle and inner
Outer layer
visible from the EAC
Middle layer:
tough, fibrous, connective tissue that
contributes the ability of the TM to vibrate to
sounds
Inner Layer:
lined with mucous membrane which is
consistent with the middle ear
The TM is very rich in
blood supply (vascular
Tympanic Membrane Responsible for
initiating
mechanical impedance-matching
process of middle ear
First layer
outer (cuticular) layer
Second layer
Intermittent (fibrous) layer
Third layer
inner (mucous) layer
Middle Ear Impedance Matcher
The area of the TM is 17 times that of
the oval window
– This allows for a sound pressure increase
in the middle ear to transfer the pressure
to the inner ear via the oval window
– The increase is needed due to a transfer
of sound from air to fluid in the inner ear
The TM is NOT
100% efficient as an
impedance matcher
Middle Ear Impedance Matcher
Increased
pressure and the lever action
of the malleus result in a pressure
increase of 23 times that of an airborne
transmission alone
– This is approximately a 30 dB increase
– A 28 dB loss would result due to the air
to fluid impedance mismatch without the
ossicles
middle ear Contains
the three smallest bones of
the body
* Bones of middle ear called ossicles
Ossicular chain: collective name for
ossicles
Malleus
– Incus
– Stapes
* Transmit acoustic energy from TM
Malleus
Largest of the ossicles
* Nine mm long and weighs only 25 mg
– Provides point of attachment with tympanic
membrane
– Bulk of bone is the head or caput
The manubrium (handle) of the malleus is
embedded in the middle (fibrous) layer of the
TM and extends to the center of the TM of the
area of greatest retraction (umbo)
Incus
Shaped like an anvil
– Weighs 30 mg and is around 7 mm long
– Provides intermediate link of ossicular chain
– Incus and malleus articulate by means of a
saddle joint
Stapes (stirrup)
Third bone of ossicular chain
– Weighs 4 mg with an area of 3.5 mm2
– Helps to transmit sound vibrations from
eardrum to oval window
– Articulation of the incus and stapes of ball
and socket type
Ossicular chain is held
in place by
ligaments
