738
UNIT FIVE
so mucus secretions drain from the sinuses into the nasal cav-
ity. Membranes that are infl amed and swollen because of nasal
infections or allergic reactions (sinusitis) may block this drain-
age, increasing pressure in a sinus and causing headache.
The sinuses reduce the weight of the skull. They also serve
as resonant chambers that affect the quality of the voice.
Sinuses
Recall from chapter 7 (pp. 208 and 212) that the
sinuses
(para-
nasal sinuses) are air-F lled spaces in the
frontal, sphenoid,
eth-
moid,
and
maxillary bones
of the skull
(f g. 19.4)
. These spaces
open into the nasal cavity and are lined with mucous mem-
branes that are continuous with the lining of the nasal cavity,
Frontal sinus
Nostril
Hard palate
Uvula
Tongue
Epiglottis
Hyoid bone
Larynx
Trachea
Superior
Middle
Inferior
Sphenoidal sinus
Pharyngeal tonsil
Nasopharynx
Opening of
auditory tube
Palatine tonsil
Oropharynx
Lingual tonsil
Laryngopharynx
Esophagus
Nasal
conchae
Mucus
Particle
Goblet cell
Cilia
Nasal cavity
Epithelial cell
(b)
(a)
FIGURE 19.2
Major structures associated with the respiratory tract in the head and neck.
FIGURE 19.3
Mucus movement in the respiratory tract. (
a
) Cilia move mucus and trapped particles from the nasal cavity to the pharynx.
(
b
) Micrograph of ciliated epithelium in the respiratory tract (275×).
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