|Biol 1152L Name ________________________________________
Ear, Hearing, Equilibrium Day & Lab time _______________________________________
You should be familiar with the following terms before coming to lab. Look up the functions of each of the following structures.
Auricle (pinna) ________________________________________________________________________
External auditory meatus (canal) __________________________________________________________
Tympanic membrane ___________________________________________________________________
Auditory ossicles _______________________________________________________________________
Eustachian tube _______________________________________________________________________
Semicircular canals _____________________________________________________________________
Oval Window __________________________________________________________________________
Round Window ________________________________________________________________________
Outer ear 3. Inner ear
Auricle (pinna) a. Vestibule
External auditory meatus (canal) i. Saccule
Middle ear ii. Utricle
Tympanic membrane b. Semicircular canals
Ossicles i. Semicircular duct
Malleus ii. Ampulla
Incus c. Cochlea
Stapes i. Organ of Corti
Oval window ii. Cochlear duct
Round window d. Vestibulocochlear nerve
Eustachain (auditory) tube i. Vestibular nerve
Inner ear ii. Cochlear nerve
Table 1: Ear Model Inventory
II. Lab Exercises: Hearing
Two clinical tests are used to determine hearing loss, the Weber test and the Rinne test. Conductive hearing loss results from interference of sound conduction through the outer and/or middle ear. Sensorineural hearing loss results from damage to the inner ear or the vestibuolcochlear nerve. A tuning fork is placed directly on the bones of the skull to evaluate bone conduction, the ability to hear the vibrations transmitted through the bone. The for is then placed near the ear, not touching bone, to evaluate air conduction, the ability to hear the vibrations transmitted through the air.
1. Obtain a tuning fork with a frequency of 500-1,000 Hz.
2. Hold the tuning fork by the base, and strike it lightly. The fork should begin ringing softly. If it is ringing
too loudly, grasp the tines to stop it from ringing, and try again.
3. Place the base of the vibrating tuning fork on the midline of your partner’s head.
4. Ask your partner if the sound is heard better in one ear or if the sound is heard equally in both ears. If
the sound is heard better in one ear, this is called lateralization.
Was the sound lateralized? If yes, to which ear? _____________________________
5. To illustrate what it would sound like if the sound were lateralized, have your partner place his or her finger in one ear. Repeat the test.
In which ear was the sound heard better? __________________
If a patient has conduction deafness, in which ear do you think the sound will be heard most clearly (the deaf ear or the good ear)? ______________________________ Why? (If you are confused, think about your results when one ear was plugged.) ________________________________________________________________________________________________________________________________________________________________
If a patient has sensorineural deafness, in which ear do you think the sound will be best heard? _____________________________________________________________________
1. Strike the tuning for lightly to start it ringing.
2. Place the base of the tuning fork on your partner’s mastoid process.
3. Time the interval during which your partner can hear the sound. Your partner will have to tell you
when he or she can no longer hear the ringing.
Time interval in seconds: ___________________________________________________
4. Once your partner cannot hear the ringing, quickly move the still-vibrating tuning fork 1-2cm lateral to
the external auditory canal (the fork should not be touching your partner at this points).
5. Time the interval from the point when you moved the tuning fork in front of the external auditory
canal to when your partner can no longer hear the sound.
Time interval in seconds: ______________________________
Which situation tested bone conduction? _______________________________
Which situation tested air conduction? _________________________________
6. Typically, the air-conducted sound is heard twice as long as the bone-conducted sound. For example,
if the bone-conducted sound was heard for 15 seconds, the air-conducted sound should be heard for
Were your results normal? _____________________________________________________
What type of deafness is present if the bone-conducted sound is heard longer than the air-conducted
Otosclerosis is a condition that results in irregular ossification (bone formation) around the stapes bone. Would you expect this to result in conductive or in sensorineural hearing loss? What results would you expect from the Rinne and Weber tests in an individual with otosclerosis?