1. The Ear: Hearing and Balance
The three parts of the ear are the inner, outer, and middle ear
outer and middle ear= hearing
inner ear= hearing and equilibrium
Receptors for hearing and balance:
Respond to separate stimuli
Are activated independently

2. The Ear: Hearing and Balance
Figure 15.25a

3. The auricle (pinna) is composed of:
Outer Ear
The auricle (pinna) is composed of:
The helix (rim)
The lobule (earlobe)
External auditory canal
Short, curved tube filled with ceruminous glands
Secretes cerumen (ear wax)

4. Tympanic membrane (eardrum)
Outer Ear
Tympanic membrane (eardrum)
Boundary between outer and middle ears
Thin connective tissue membrane that vibrates in response to sound
Transfers sound energy to the middle ear ossicles

5. Middle Ear (Tympanic Cavity)
A small, air-filled, mucosa-lined cavity
Pharyngotympanic (auditory) tube – connects the middle ear to the nasopharynx
used to be called the eustachian tube
Equalizes pressure in the middle ear cavity with the external air pressure (i.e. ‘popping’ ears at changing altitudes)

6. Middle and Internal Ear
Figure 15.25b

7. Ear Ossicles
The tympanic cavity contains three small bones: the malleus, incus, and stapes
Hammer, anvil, and stirrup
Transmit vibratory motion of the eardrum to the oval window

8. Ear Ossicles
Figure 15.26

9. Chunk and Chew: Partner A: Partner B:
Please describe the function and anatomical parts of the outer ear.
Partner B:
Please describe the anatomical parts of the middle ear. How does sound travel here?

10. Inner Ear Bony labyrinth Membranous labyrinth
Channels worming their way through the temporal bone
Three regions:
Vestibule, cochlea, and semicircular canals
Membranous labyrinth
Series of membranous sacs within the bony labyrinth
Filled with a potassium-rich fluid

11. Inner Ear
Figure 15.27

12. The utricle (bottom section) extends into the semicircular canals
The Vestibule
The utricle (bottom section) extends into the semicircular canals
These sacs:
House equilibrium receptors called maculae
Respond to gravity and changes in the position of the head

13. The Semicircular Canals
Three canals that each define two-thirds of a circle and lie in the three planes of space
These receptors respond to angular movements of the head

14. A spiral, conical, bony chamber that:
The Cochlea
A spiral, conical, bony chamber that:
Contains the cochlear duct
Contains the organ of Corti (hearing receptor)-aides in processing pitch, frequency, etc.

15. Check it out!

16. Sound and Mechanisms of Hearing
Sound vibrations beat against the eardrum
The eardrum pushes against the ossicles, which presses fluid in the inner ear against the oval and round windows
This movement sets up shearing forces that pull on hair cells
Moving hair cells stimulates the cochlear nerve that sends impulses to the brain

17. Lets look at how they work!!!

18. Properties of Sound
Frequency – the number of waves that pass a given point in a given time
Pitch – perception of different frequencies (we hear from 20–20,000 Hz)

19. Amplitude – intensity of a sound measured in decibels (dB)
Properties of Sound
Amplitude – intensity of a sound measured in decibels (dB)
Loudness – subjective interpretation of sound intensity
Figure 15.29

20. Frequency and Amplitude
Figure 15.30

21. Chunk and Chew: Partner A: Partner B: Both partners:
Please explain to your partner the anatomical parts and functions of the inner ear.
Partner B:
Please describe the properties of sound…what aspect of waves do we hear?
Both partners:
Follow the path of sound from the outer ear to the cochlea.