Transcript Ears - science105

PowerPoint® Lecture Slide Presentation
by Patty Bostwick-Taylor,
Florence-Darlington Technical College
Ears and
Hearing
8
PART B
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomy of the Ear
 The ear is divided into three areas
 External (outer) ear
 Middle ear (tympanic cavity)
 Inner ear (bony labyrinth)
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The Ear
 Houses two senses
 Hearing
 Equilibrium (balance)
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomy of the Ear
Figure 8.12
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
The External Ear
 Involved in hearing only
 Structures of the external ear
 Auricle (pinna)
 Funnels sound waves
 External acoustic meatus (auditory canal)
 Narrow chamber in the temporal bone
 Lined with skin and ceruminous (wax)
glands
 Ends at the tympanic membrane
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Why wax?
 The actual wax that is observed is the coating
of the inside of your ear in order to protect it
from things entering the ear canal. Ear wax is
produced by a gland that is inside your ear, to
help keep away dirt, bugs, and even germs.
When your ears are not cleaned for a long
time, the wax eventually just dries up and falls
out in tiny, flaky bundles that you don't even
realize.
 ~D.W.
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
The Middle Ear (Tympanic Cavity)
 Air-filled cavity within the temporal bone
 Only involved in the sense of hearing
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
The Middle Ear (Tympanic Cavity)
 The opening from the auditory canal is covered by
the tympanic membrane
 Tympanic Membrane - vibrates in response to
pressure changes
 The auditory tube connects the middle ear with
the throat
 Allows for equalizing pressure during yawning
or swallowing
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomy of the Ear
Figure 8.12
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
The auditory tube
 If pressure outside is greater than inside, ears will
“pop”
 Chewing gum can help equalize pressure
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Ear Infections (Otitis media)
 Don’t close nostrils when blowing nose, can force
debris into the ears causing infection of the
middle ear (otitis media)
 Frequent ear infections can receive “tubes” for
drainage
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Bones of the Middle Ear (Tympanic Cavity)
 Three bones (ossicles) span the cavity
 Malleus (hammer)
 Incus (anvil)
 Stapes (stirrip)
 Function
 Vibrations from eardrum move the Malleus 
Incus  Stapes  inner ear
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomy of the Ear
Figure 8.12
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Inner Ear or Bony Labyrinth
 Vibrations enter through the oval window from the
Stapes
 Vibrations move perilymph fluid in:
 Semicircular canals
 Sensing equilibrium
 Vestibule
 Connects semicircular canals to cochlea
 Cochlea
 Contains the hairs for hearing senses
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Cochlea
 Hair Cells
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A sense of hearing
 Cell membrane protein channels open in
response to changes in frequencies
 Allow Ca+2 ions to flow into the cells
 Triggers neurotransmitter release
 Sends signal through vestibulocochlear nerve to
the brain
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomy of the Ear
Figure 8.12
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Decibels (dB) - measure sound intensity
 0 dB - least perceptible by humans
 40 dB - whispering
 60-70 dB - normal conversation
 80 dB - heavy traffic
 90 dB - above this can damage hearing receptors
 120 dB - Rock concert
 140 dB - Jet plane takeoff
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Partial or complete hearing loss
 Eardrum can harden as a result of disease
 Eardrum can tear or perforate due to disease or
injury
 Loud sounds, tumors, brain damage or drug use
can damage nerve pathways
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings