Special Senses

The sense of hearing

Enhances one's life
Makes communication easier

The structure of the ear is divided into 3 regions

Outer Ear

• Sound waves enter the ear through the pinna, or auricle, which is the projecting part or flap of the ear

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• The external auditory meatus (auditory canal) leads from the pinna and is lined with numerous glands that secrete a yellowish brown, waxy substance called cerumen, which lubricates and protects the ear.

Middle Ear

• sound waves travel through the auditory canal and strike a membrane, or eardrum

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• As the eardrum vibrates, it moves three small bones or ossicles
• Malleus, Incus, Stapes

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• Auditory or Eustachian tube
• Is a canal leading from the middle ear to the pharynx
• It is normally closed, but opens on swallowing to equalize pressure.

Inner Ear

• Sound vibrations reach the inner ear via the fluctuation of the oval window that separates the middle and inner ears
• sometimes called the labyrinth

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• Cochlea:
• contains special auditory liquids through which the vibrations travel
• Organ of corti: sensitive auditory receptor
• Auditory nerve fibers end in the auditory center of the cerebral cortex, where the impulses can be "heard"

Equilibrium

• The ear is an imprtant organ of equilibrium (balance)
• Vestibule connects the cochlea (for hearing) to three semicircular canals for balance