Page 255 - Anatomy and Physiology of Farm Animals, 8th Edition

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VetBooks.ir Helicotrema

Vestibular window

Scala vestibuli
Cochlear duct

Scala tympani

Vestibular membrane

Tectorial membrane Scala vestibuli
Cochlear
Primary afferents of duct
cochlear nerve Hair cells

Scala tympani

Basilar membrane
Figure 12-8. Schematic of the function of the cochlea. The scalae and cochlear duct are depicted in the
top portion of this figure unwound for clarity; below is a cross‐section showing the details of the fluid‐
filled spaces and the spiral organ. Red arrow above indicates vibrations of the vestibular window which
sets up pressure waves (yellow arcs) in the perilymph of the scala vestibuli. At a particular region of the
cochlear duct these pressure waves will produce a resonant vibration in the basilar membrane (red arrow,
below). The moving hair cells are bent against the overlying tectorial membrane, depolarizing them.

window, which abuts the air‐filled space of scalae vestibuli and tympani are called
the middle ear. the vestibular and basilar membranes,
The receptor cells of the auditory system respectively.
are within the cochlear duct as compo­ Cross‐sectional views of the cochlea
nents of the spiral organ (organ of Corti) give the impression that the components
(Figs. 12‐7 and 12‐8). The spiral organ within are arrayed as repeating separate
contains the receptor cells of the internal units, but they are longitudinally contin­
ear, mechanoreceptors called hair cells uous throughout the extent of the spiraled
for the bundle of cilia on their apex. The cochlea.
cilia of the hair cells in the spiral organ are The hair cells synapse with peripheral
embedded in a relatively stiff overlying processes of primary afferent neurons
membrane, the tectorial membrane. The whose cell bodies lie within the spiral gan­
walls between the cochlear duct and the glion. The spiral ganglion is housed in the