CHAPTER 3
Epithelium and Glands
37
Pseudostratif
ed Columnar Epithelium
Figure 3-9A.
Pseudostratif
ed ciliated columnar
epithelium, trachea.
H&E,
3
155; inset
3
247
The cells of
pseudostratif ed ciliated columnar
epithelium
vary in shape and height, and their nuclei
are staggered, giving the false impression of being
arranged in two or three layers of cells. However, the
basal aspect of each cell is in contact with the
base-
ment membrane
. Most cells are tall and columnar,
but there are also short basal cells, some of which are
stem cells
. The most widespread type of pseudostrati-
F ed columnar epithelium is
ciliated
and is found lining
the trachea and primary bronchi, the auditory tube,
and part of the tympanic cavity.
Nonciliated
pseu-
dostratiF ed columnar epithelium is found throughout
the epididymis and vas deferens in the male reproduc-
tive tract. Cilia on the apical surfaces of some cells are
closely packed like bristles of a brush. The pink line
indicated by the
arrow
(
inset
) is formed by the
basal
bodies
, from which the cilia arise. The arrangement of
the nuclei in pseudostratiF ed columnar epithelium is
more irregular than in stratiF ed columnar epithelium.
Figure 3-9B.
A representation o± the pseudostrat-
if
ed ciliated columnar epithelium o± the trachea.
Secretory goblet cells
are interspersed among the
ciliated columnar cells
. Cilia are elongated, motile
structures that are about 5 to 10 times longer than
microvilli. The core of a cilium is composed of
microtubules
, which are inserted into
basal bodies
,
electron-dense structures in the apical cytoplasm just
below the cell membrane. The function of cilia is to
aid in the transport of material along the surface of
the cells, such as moving mucus and particulate mat-
ter out of the respiratory tract.
Basal cells
are short,
located in the basal portion of the epithelium, and do
not reach the lumen. The epithelium may appear to
have more than one layer; in fact, all of its cells are
in contact with the
basement membrane
.
Cilia
Pseudostratified
Pseudostratified
columnar
columnar
epithelium
epithelium
B
a
s
a
l b
l
b
o
d
ie
i
e
s
B
a
s
e
m
e
n
t
m
m
e
m
b
ra
r
a
n
e
Cilia
Pseudostratified
columnar
epithelium
Basal bodies
Basement
membrane
A
D. Cui
D. Cui
Ciliated columnar cell
Cilia
Basal body
Basement membrane
Cilia, basal body,
and microtubules
Connective
tissue
Goblet cell
Basal cell
Basal body
B
CLINICAL CORRELATION
Figure 3-9C.
Bronchitis.
Bronchitis
is a disease marked by acute or chronic infl ammation
of the bronchial tubes (bronchi). The infl ammation may be caused
by
in±ection
(virus, bacteria) or by
exposure to irritants
(smoking
or inhalation of chemical pollutants or dust.) Cigarette smoking is
the leading cause of chronic bronchitis. The infl ammatory process
inhibits the characteristic activity of
cilia
,
which is to trap and
eliminate pollutants. Infl ammation also increases the secretion of
mucus
. The infl amed area of the bronchial wall becomes swollen,
and excess mucus may obstruct the airway. In
chronic bronchitis
,
the surface epithelium may undergo
hyperplasia
and
loss o± cilia
;
the pseudostratiF ed epithelium is often replaced by squamous epi-
thelium. This process is called
squamous
metaplasia
.
D. Cui
Hyperplastic columnar cell
Mucus
Remaining basal body
Loss of cilia
Inflammatory cells in
the connective tissue
Squamous cell
C
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