1. Special Senses- The Ear
Module 13

2. The Ear at a Glance Function of the Ear Structures of the Ear
Contains sensory receptors for hearing and equilibrium (balance)
Structures of the Ear
Auricle
External ear
Middle ear
Inner ear

4. Anatomy and Physiology
Otology (Oto) is study of the ear
Audiology is study of hearing disorders
Ear responsible for two senses:
Hearing
Equilibrium or sense of balance
Sensory information carried to brain by vestibulocochlear nerve
Cochlear nerve – hearing information
Vestibular nerve – balance information

5. The Ear Ear is subdivided into three regions: External ear Middle ear
Inner ear

6. External Ear Auricle or pinna Only portion visible
Captures sound waves
Directs them through external auditory meatus

7. External Ear Auditory canal Cerumen Sound moves along canal
Produced by oil glands in auditory canal
Oily wax slowly flows out of ear canal removing dirt that has stuck to it

8. External Ear Tympanic membrane
Commonly called eardrum
Sound waves strike membrane
Causes it to vibrate
Tympanic membrane separates external ear from middle ear

9. The internal structures of the outer, middle,
and inner ear.

10. The Middle Ear Small cavity Located in temporal bone of skull
Contains three tiny bones called ossicles
Malleus
Incus
Stapes

11. Ossicles Tympanic membrane vibrates incus
Vibrations amplify as they move from one ossicle to next
Stapes transmits vibration to oval window
Start of inner ear

12. Eustachian Tube Also called auditory tube
Connects nasopharynx with middle ear
Opens with each swallow
Equalizes pressure between middle ear cavity and atmospheric pressure

13. The internal structures of the outer, middle,
and inner ear.

14. Inner Ear Labyrinth Contains sensory organs
Cavity within temporal bone
Houses inner ear
Contains sensory organs

15. Sensory Organs of Inner Ear
Hearing
Cochlea
Organs of Corti
Equilibrium
Semicircular canals
Utricle
Saccule

16. How We Hear
Sound waves travel down external auditory canal, strike eardrum
Eardrum vibrates

17. How We Hear
Ossicles conduct vibrations across middle ear from eardrum to oval window
Oval window movements initiate vibrations in fluid that fills cochlea
Fluid vibrations strike hair cells, bending small hairs and stimulating nerve endings
Nerve ending sends electrical impulse to brain on cochlear portion of vestibulocochlear nerve

18. Hearing Loss Conductive hearing loss
Disease or malformation of outer or middle ear
All sound is weaker and muffled since it is not conducted correctly to inner ear
Sensorineural hearing loss
Damage or malformation of inner ear (cochlea) or the cochlear nerve
Sounds are distorted because nerve impulse is incorrect

21. REMEMBER
Pronunciation of terms test is due at end of module 14. Have any questions- post on the discussion board!

22. Next up: special topics
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