The vestibular apparatus of the inner ear contains
that detect rotation of the head in space, linear accel-
eration, and the static position of the head. The sensory recep-
that are similar in many, but not all, respects
to the hair cells of the auditory system (see Fig. 21-11A,B).
of the head are detected by hair cells
located in the
of the anterior, posterior, and
(located within their respective
is detected by hair
cells in the macula of the utricle;
by hair cells in the macula of the saccule.
detected by combining signals from the maculae of the utricle
and saccule. The
indicates the approximate
position of the photomicrograph in Figure 21-8B.
Crista ampullaris and macula utriculi.
A low-power photomicrograph that includes the
of a semicircular canal, the
, and a portion of the
The semicircular canal within the temporal bone is ± lled with
. The membranous labyrinth, ± lled with endolymph, ﬂ oats
within this bony canal (Fig. 21-2). The sensory receptors of both the vestibular system and the auditory system are in contact
with the endolymph. The
contains vestibular hair cells and the sensory receptors of the vestibular system and is
described in detail in Figure 21-9A,B. A gelatinous structure, the
, surrounds the crista ampullaris and forms a wall across
the ampulla (Fig. 21-9A). The cupula is normally lost during tissue processing. Movement of the endolymph during head rotation
deﬂ ects the cupula and, thereby, bends the cilia of the hair cells. The large ﬂ
lled utricle contains the
, a sense
organ that measures linear acceleration and static position of the head. The macula utriculi contains vestibular hair cells with cilia
that are embedded in a gelatinous structure, the
. This membrane is covered by tiny crystals (
have a higher speci± c gravity than the surrounding endolymph and, consequently, are inﬂ
uenced by gravity and acceleration. The
macula is described in further detail in Figure 21-10A–C.