808
UNIT 4
Maintenance of the Body
22
Te vocal folds vibrate, producing sounds as air rushes up
from the lungs. Te vocal folds and the medial opening be-
tween them through which air passes are called the
glottis
.
Superior to the vocal folds is a similar pair of mucosal folds
called the
vestibular folds
, or
false vocal cords
. Tese play no
direct part in sound production but help to close the glottis
when we swallow.
Epithelium of Larynx
Stratified squamous epithelium lines
the superior portion of the larynx, an area subject to food con-
tact. Below the vocal folds the epithelium is a pseudostratified
ciliated columnar type that filters dust. Te power stroke of its
cilia is directed upward toward the pharynx to continually move
mucus
away
from the lungs. We help move mucus up and out of
the larynx when we “clear our throat.”
Voice Production
Speech involves the intermittent release of expired air as the glot-
tis opens and closes. Te length of the vocal folds and the size of
the glottis change with the action of the intrinsic laryngeal mus-
cles that clothe the cartilages. Most of these muscles move the
arytenoid cartilages. As the length and tension of the vocal folds
change, the pitch of the sound varies. Generally, the tenser the vo-
cal folds, the faster they vibrate and the higher the pitch.
As a boy’s larynx enlarges during puberty, his vocal folds
become longer and thicker. Because this causes them to vi-
brate more slowly, his voice becomes deeper. Until the young
man learns to control his newly enlarged vocal folds, his voice
“cracks.”
Loudness of the voice depends on the force with which the
airstream rushes across the vocal folds. Te greater the force,
the stronger the vibration and the louder the sound. Te vocal
folds do not move at all when we whisper, but they vibrate vig-
larger in males than in females because male sex hormones
stimulate its growth during puberty. Inferior to the thyroid car-
tilage is the ring-shaped
cricoid cartilage
(kri
9
koid), perched
atop and anchored to the trachea inferiorly.
Tree pairs of small cartilages—
arytenoid
(ar
0
ĭ-te
9
noid),
cuneiform
(ku-ne
9
ĭ-form), and
corniculate cartilages
—form
part of the lateral and posterior walls of the larynx. Te most
important of these are the pyramid-shaped arytenoid cartilages,
which anchor the vocal folds.
Epiglottis
Te ninth cartilage, the flexible, spoon-shaped
epi-
glottis
(ep
0
ĭ-glot
9
is; “above the glottis”), is composed of elastic
cartilage and is almost entirely covered by a taste bud–containing
mucosa. Te epiglottis extends from the posterior aspect of the
tongue to its anchoring point on the anterior rim of the thyroid
cartilage (Figure 22.4b and c).
When only air is flowing into the larynx, the inlet to the lar-
ynx is wide open and the free edge of the epiglottis projects
upward. During swallowing, the larynx is pulled superiorly and
the epiglottis tips to cover the laryngeal inlet. Because this ac-
tion keeps food out of the lower respiratory passages, the epi-
glottis has been called the guardian of the airways. Anything
other than air entering the larynx initiates the cough reflex to
expel the substance. Tis protective reflex does not work when
we are unconscious, so it is never a good idea to administer liq-
uids when attempting to revive an unconscious person.
Vocal Folds
Lying under the laryngeal mucosa on each side
are the
vocal ligaments
, which attach the arytenoid cartilages
to the thyroid cartilage. Tese ligaments, composed largely of
elastic fibers, form the core of mucosal folds called the
vocal
folds
, or
true vocal cords
, which appear pearly white because
they lack blood vessels
(Figure 22.5)
.
(a) Vocal folds in closed position; closed glottis
(b) Vocal folds in open position; open glottis
Base of tongue
Epiglottis
Vestibular fold (false vocal cord)
Vocal fold (true vocal cord)
Glottis
Inner lining of trachea
Cuneiform cartilage
Corniculate cartilage
Figure 22.5
Movements of the vocal folds.
Drawings of superior views of the larynx and
vocal folds, as if looking at a patient’s larynx through a laryngoscope.
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