CHAPTER 11
Respiratory System
205
Conducting Portion: Upper Respiratory Airway
Figure 11-3A.
Nasal vestibule, nose.
H&E,
3
12; insets
3
42 (
left
);
3
34 (
right
)
The nasal cavity contains pairs of chambers separated by the nasal
septum; the air passing through these chambers is moistened and
warmed before it enters the lungs. There are three types of epithelia
lining the nasal cavity in different regions: (1) the
vestibule region
is
lined by stratiF ed squamous epithelium; (2) the
nasal mucosa region
is
lined by respiratory epithelium, which occupies most of the area in the
nasal cavity, such as the
conchae
and nasal cavity wall; (3) the
olfac-
tory mucosae
are covered by a specialized olfactory epithelium and
are concerned with the sense of smell (±igs. 11-1 and 11-4). The exter-
nal surface of the
nasal vestibule
is covered by the skin and its internal
surface is covered by stratiF ed squamous epithelium with numbers of
vibrissae
(stiff hairs) that entrap dust particles and prevent them from
entering the lungs. The vibrissae are greater in number at the anterior
end and gradually decrease at the posterior end of the vestibule.
Seba-
ceous glands
are found around the roots of the
vibrissal follicles
.
A
Sebaceous
Sebaceous
gland
gland
Sebaceous
gland
Sebaceous
Sebaceous
gland
gland
Sebaceous
gland
Vibrissal
follicles
Vibrissal
Vibrissal
follicles
follicles
Vibrissal
follicles
Skin
B
Lamina
propria
Respiratory epithelium
Bone
Bone
Bone
Venous
Venous
plexuses
plexuses
Venous
plexuses
Figure 11-3B.
Nasal mucosa, nose.
H&E,
3
42
Nasal mucosa
lines most of the nasal cavity. It is made up of
respira-
tory epithelium
(a layer of ciliated pseudostratiF ed columnar epithe-
lium) and a layer of connective tissue beneath the
lamina propria
. The
nasal mucosa is attached to the bone for skeletal support. Respiratory
epithelium is composed of ciliated cells, goblet cells, and basal cells
as well as rarer cell types such as endocrine cells (±ig. 11-7; see also
±igs. 3-9 and 3-10). This type of epithelium lines most regions of the
respiratory system. There are many blood vessels (
venous plexuses
) in
the lamina propria of the nasal mucosa; these small veins provide a
rich blood fl ow, which warms the air passing through the nasal cavity
before air enters the lungs.
The large venous plexuses within the lamina propria of the nasal
conchae are called
swell bodies
. Small arteries empty blood directly
into the venous plexuses within the conchae; this causes the lam-
ina propria to swell, reducing airfl
ow through the nasal cavity and
increasing air contact with the nasal mucosa.
C
Small vein
Capillaries
MALT
Bone
Figure 11-3C.
Nasal mucosa, nose.
H&E,
3
70
Lymph nodules or diffuse lymphocytes are often found in the lamina
propria of the nasal mucosa, bronchi, and bronchioles (±ig. 11-10B).
They are called
mucosa-associated lymphatic tissue
(
MALT
) and are
usually located in the connective tissue where they can inF ltrate the
epithelium (see
inset
). The lymphoid tissues immunologically support
the wet epithelial membranes of the body’s mucosae and can be found
in mucosae of other organs, such as the appendix and the ileum of the
digestive tract (see Chapter 10, “Lymphoid System,” ±ig. 10-9A and
Chapter 15, “Digestive Tract,” ±ig. 15-15). Mucous and mixed muco-
serous glands may be found in the lamina propria in some specimens.
In response to upper respiratory airway infection or allergic reac-
tion, the nasal mucosa may become swollen (especially the inferior
concha) and infl
amed, blocking air passage through the nasal cav-
ity. This condition is called
rhinitis
. Symptoms may include a stuffy
or runny nose; common treatments are antihistamine and decon-
gestant pills and sprays, etc.
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