Chapter 9/10 Flashcards
What is the purpose of the ear?
The ear as a transducer that changes acoustic energy into electrochemical energy (sound-mechanical-electrical)
Pinna
A collector of sound energy, cartilage, covered with epithelial tissue with fine hair, helps with localization, resonating cavity, funnels sound into ME
Concha
Deepest depression
Helix
Rim-like ridge surrounding pinna
Antihelix
Runs inside the helix
Tragus
cartilage on anterior wall
Antitragus
Opposite of the tragus, bottom ridge on concha
External Auditory Meatus (Ear Canal)
7 mm diameter, 2.5 cm length, resonating cavity, lateral 1/3 cartilage, medial 2/3 bon meatus, s shaped, lined with hair in outer 1/3, secretes cerumen
Tympanic membrane
Eardrum, sits with a tilt, 3 layers (epithlial, fibrus, mucous), separates OE from ME, can see the beginning of the ossicles
What is acoustic energy?
The disturbance of energy which passes through a material in the form of waves (through any medium)
What happens in the ossicles?
The acoustic energy is transferred into mechanical energy
What are the most important muscles in the ME?
Tensor Tympani Muscle, Stapedius muscle
Malleus
largest, attaches to Tm
Incus
connects malleus and stapes, saddle joint
Stapes
connects the oval window, smallest
What is the purpose of the ossicular chain?
To transmit acoustic energy across the bones from the TM to the inner ear
Is the ME filed with air?
Yes
What is the ME function?
To increase the pressure appreaching the cochlear (impedence)/match the impedence of the 2 systems (OE and cochlea)
Impedance
Overcoming resistance to flow of energy
How does the ME overcome impedence?
Total area from TM to OW is a 25 db gain–> lever action is 2 db and bucking is 4-6 db
What is mechanical energy?
The energy of an object due to its motion or position (sum of kinetic and potential energy)
What is the purpose of the IE?
Sensor for balance and hearing
Balance
Vestibular
Hearing
Cochlear
The bony labyrinth
vestibue, ssc, cochlea
What is the outer bony labyrinth lined with ?
perioseum
Wha is the function of the vestibular system?
It gives us an idea of where we are in space. When the head turns, fluid in one or more ssc ducts pushes against the cupula and bends the cilia of the hair cells- fluid in the corresponding ssc on the opposite side moves in the opposite direction
Periosteum
A complex structure composed on an outer fibrous layer that lends structural integrity and inner cambium later that possess osteogenic potential
Basilar Membrane
extra cellular matrix that lines the basal side of epithelial and endothelia tissues- it produces physical and biochemical cues to the cells (it is made of basal lamina and reticular lamina)
Vestibular membrane
membrane inside the cochlea of the inner ear and it separates the cochlear duct from the vestibular duct (dividing wall)
Where does fluid of the IE come from?
Perilymphtic fluid is secreted by the epithelial lining of the bony labryinth
Is the cochlear filled with fluid?
yes
IE (cochlea) function
the cochlea is specifically designed to sort out the frequency components of an incoming signal, determine amplitude, and identify basic temporal aspects of that signal. The BM carries the traveling sound wave which the movement of the hair cells is creating
How do the waves work?
Different frequencies reach their peak as different positions along the membrane (base= high apex=low)
What is the vestibulocochlear nerve? (VIII)
- Vestibular branch- carries info from receptors in the IE responsible for equilibrium
- Cochlear branch- carries info from receptors in the cochlea responsible for hearing
Where is the signal initialy registered?
In the brainstem (pons and medulla)
Otitis Media
Fluid in ME, Eustachian tube not draining, ME bones are anaerobic (without air), pressure is not equalized (negative)
Mastoiditis
Inflammation/infection of the mastoid bone (could lead to deafness, infection in the brain, or death), bacteria is coming from the eustachian tube
Otitis Externa
Inflammation of the skin of the external ear, swelling, swimmers ear, facial paralysis bc the root of the nerve is close to the inner ear, hearing loss
Other pathologies
OM, OE, congenial issues, traumatic lesions, neoplastic changes, tumors, bone changes, ssc dehiscence
Tympanometry
Impedance of the ME
High Resolution MRI
Structural Architechture
Clinical Audiometry
Behavioral Assessment of hearing/screenings
Evoked Auditory Brainstem response
integrity of the early stages of the auditory pathway
Electrocochleography
integrity of the auditory pathway
Functional Magnetic Resonance Imaging
auditory cortical functioning
Otoacoustic Emissions Testing
tones into the ear, reflections from the cochlea/health of hair cells