During normal breathing the vocal cords remain relaxed,
and the opening between them, called the
a triangular slit. However, when food or liquid is swallowed,
muscles close the glottis in the false vocal folds. Along with
closing of the epiglottis, this action helps prevent food or liq-
uid from entering the trachea
(f g. 19.7)
. The mucous mem-
brane that lines the larynx continues to F lter incoming air by
entrapping particles and moving them toward the pharynx
by ciliary action.
What part of the respiratory tract is shared with the alimentary
Describe the structure of the larynx.
How do the vocal cords produce sounds?
What is the function of the epiglottis? Of the glottis?
vocal cords during speech and aid in closing the larynx dur-
are small, cylindrical struc-
tures in the mucous membrane between the epiglottic and the
arytenoid cartilages. They stiffen the soft tissues in this region.
Inside the larynx, two pairs of horizontal folds com-
posed of muscle tissue and connective tissue with a covering
of mucous membrane extend inward from the lateral walls.
The upper folds (vestibular folds) are called
false vocal cords
because they do not produce sounds. Muscle F
these folds help close the larynx during swallowing.
The lower folds are the
true vocal cords.
They have elastic
F bers and are responsible for vocal sounds, which are created
when air is forced between these folds, vibrating them. This
action generates sound waves, formed into words by chang-
ing the shapes of the pharynx and oral cavity and by using the
tongue and lips.
shows both pairs of cords.
Changing tension on the vocal cords, by contracting or
relaxing laryngeal muscles, controls
(musical tone) of
the voice. Increasing the tension produces a higher pitch,
and decreasing the tension creates a lower pitch.
(loudness) of a vocal sound depends upon
the force of the air passing over the vocal cords. Stronger
blasts of air result in greater vibration of the vocal cords and
) Anterior and (
) posterior views of the larynx.
False vocal cord
) Frontal section and (
) sagittal section of