1. The Ear Houses two senses 1) Hearing 2) Equilibrium (balance)
Mechanoreceptors – receptors that respond to physical forces; both respond to movements of fluid
Different organs house receptors for each sense and are independent of each other.

2. Anatomy of the Ear The ear is divided into three areas
1) Outer (external) ear
2) Middle ear
3) Inner ear
Figure 8.12

3. The External Ear Involved in hearing only
Structures of the external ear
1) Pinna (auricle)
2) External auditory canal
Figure 8.12

4. The External Auditory Canal
Narrow chamber in the temporal bone
Lined with skin
Ceruminous (wax) glands are present
Ends at the tympanic membrane

5. The Middle Ear or Tympanic Cavity
Air-filled cavity within the temporal bone
Only involved in the sense of hearing

6. The Middle Ear or Tympanic Cavity
Tympanic membrane (Eardrum) – Skin covering the opening of the middle ear; stretched tight to sense vibrations like a drum head.
Auditory tube connects the middle ear with the throat
Allows for equalizing pressure during yawning or swallowing; otherwise this tube is collapsed

7. The Middle Ear or Tympanic Cavity
Homeostatic Imbalance
Otitis Media (Ear Infection) – inflammation of the middle ear.
Symptoms: eardrum bulges from large amounts of fluid in the cavity as it fights the infection. The pressure causes pain and can rupture the eardrum
Tubes can be placed in the eardrum so that the fluids drain to relieve pressure

8. The Middle Ear or Tympanic Cavity
Homeostatic Imbalance: Otitis media continued
Usually results from bacteria infection in the throat area; sore throat.
Problem in small children whose auditory tube runs more horizontal
Don’t “prop” a bottle or feed a baby lying flat because it can enter the tube

9. Bones of the Tympanic Cavity
Three bones span the cavity
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
Figure 8.12

10. Bones of the Tympanic Cavity
Vibrations from eardrum move the malleus
These bones transfer sound to the inner ear
If you have problems with these bones … you don’t hear!!
Figure 8.12

11. Inner Ear or Bony Labyrinth
Includes sense organs for hearing and balance
Filled with perilymph which is a plasma-like fluid
Figure 8.12

12. Inner Ear or Bony Labrynth
A maze of bony chambers within the temporal bone
3 subdivisions of the Inner Ear
1) Cochlea
2) Vestibule
3) Semicircular canals
Figure 8.12