InSight
T h e in n e r e a r
Figure 8.12
THE PLANNER^
The inner ear is divided into the outer
bony labyrinth and inner membranous
labyrinth. The bony labyrinth contains the
cochlea, the sense organ for hearing, and
the vestibule and semicircular canals, the
sense organs for equilibrium and balance.
The spiral organ (organ of Corti) is the
organ of hearing and consists of support-
ing cells and hair cells, the receptors for
auditory sensations.
Basilar membrane
Round window
a.
Internal
ear
LATERAL
Utricle
Stapes in oval window
Cochlea
MEDIAL
Arrows show direction
of fluid movement
cell
Supporting
cells
Fluid pressure waves move hair cells in
the organ of Corti. The movements
stimulate action potentials in the hair cells.
Basilar membrane
Spiral organ
(organ of Corti)
Basilar
membrane
b. Section through one turn of the cochlea
Hair
cell
Sensory and
motor fibers
in cochlear branch
of vestibulocochlear
(VIII) nerve
Spiral
ganglion
Cochlear
branch of
vestibulo-
cochlear
(VIII) nerve
c. Spiral organ (organ of Corti)
242 CHAPTER 8
Somatic Senses and Special Senses
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