740
UNIT FIVE
It is possible to illuminate a person’s frontal sinus in a darkened room
by holding a small flashlight just beneath the eyebrow. Similarly,
holding the F
ashlight in the mouth illuminates the maxillary sinuses.
PRACTICE
5
Where are the sinuses located?
6
What are the functions of the sinuses?
Pharynx
The
pharynx
(throat) is posterior to the nasal cavity, oral
cavity, and larynx. It is a passageway for food moving
from the oral cavity to the esophagus and for air passing
between the nasal cavity and the larynx (see F
g. 19.2). It
also aids in producing the sounds of speech. The subdivi-
sions of the pharynx—the nasopharynx, oropharynx, and
laryngopharynx—are described in chapter 17 (p. 663).
Larynx
The
larynx
is an enlargement in the airway superior to the
trachea (see reference plates 9 and 21). It is a passageway
for air moving in and out of the trachea and prevents foreign
objects from entering the trachea. The larynx also houses the
vocal cords
.
The larynx is composed of a framework of muscles and
cartilages bound by elastic tissue. The largest of the cartilages
are the thyroid, cricoid, and epiglottic cartilages
(f g. 19.5)
.
These structures are single. The other laryngeal cartilages—the
arytenoid, corniculate, and cuneiform cartilages—are paired.
The
thyroid cartilage
was named for the thyroid gland
that covers its lower area. This cartilage is the shieldlike
structure that protrudes in the front of the neck and is some-
times called the Adam’s apple. The protrusion typically is
more prominent in males than in females because of an effect
of male sex hormones on the development of the larynx.
The
cricoid cartilage
lies inferior to the thyroid carti-
lage. It marks the lowermost portion of the larynx.
The
epiglottic cartilage,
the only one of the laryngeal
cartilages that is elastic, not hyaline, cartilage, is attached
to the upper border of the thyroid cartilage and supports a
aplike structure called the
epiglottis.
The epiglottis usu-
ally stands upright and allows air to enter the larynx. During
swallowing, however, muscular contractions raise the lar-
ynx, and the base of the tongue presses the epiglottis down-
ward. The epiglottis partially covers the opening into the
larynx, helping prevent foods and liquids from entering the
air passages.
Posteriorly on the larynx, the pyramid-shaped
arytenoid
cartilages
are superior to and on either side of the cricoid
cartilage. Attached to the tips of the arytenoid cartilages are
the tiny, conelike
corniculate cartilages.
These cartilages
are attachments for muscles that help regulate tension on the
(a)
(b)
FIGURE 19.4
Radiograph of a skull (
a
) from the anterior view and
(
b
) from the lateral view, showing air-±
lled sinuses (arrows) within the
bones.
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