CHAPTER 3
Epithelium and Glands
35
Simple Columnar Epithelium
Figure 3-7A.
Simple columnar epithelium,
small intestine.
H&E,
3
155; inset
3
408
This is a section taken from the ileum of the small
intestine. The apical surface of the
columnar
epithelium
reveals a
brush border
, consisting of
microvilli
with a
glycocalyx
coating. Microvilli
are
F ngerlike structures that increase the surface area
of the apical membrane where absorption of nutri-
ents occurs. The cells with seemingly empty cyto-
plasm are
goblet cells
, which are mucus- secreting
cells interspersed among the simple columnar
absorptive cells
(enterocytes)
. The nuclei of the epi-
thelial cells are elongated, “hot-dog” shaped, and
located toward the basal end of the cells. Some-
times, the simple columnar epithelium appears to
be multilayered because of the cutting angle, but
only a single layer of cells actually attaches to the
basement membrane.
Simple columnar epithelium
is typical of the lining of the digestive tract, and
it is also found in the ov ducts, ductuli efferentes,
and the ducts of some exocrine glands.
A
Brush border
Brush border
Brush border
Simple columnar
Simple columnar
epithelium
epithelium
Simple columnar
epithelium
Brush border
Brush border
Brush border
Goblet
Goblet
cell
cell
Goblet
cell
Simple
Simple
columnar
columnar
epithelium
epithelium
Simple
columnar
epithelium
Figure 3-7B.
A representation of simple
columnar epithelium in the small intestine.
In the small intestine,
microvilli
enhance
digestive
and absorptive functions by increasing the area
of the surface membrane of each
columnar epi-
thelial cell
. This provides an expanded area of
interface between the cell surface and the nutri-
ents in the lumen. Each microvillus has a core that
is composed of
actin micro±
laments
anchored in
a
terminal web
to stabilize the microvillus. Tall
and slender columnar cells and the relationship
of the terminal web are illustrated here. Indi-
vidual microvilli, actin microF
laments, and actin
F laments of the terminal web cannot be seen
under light microscope.
B
D. Cui
D. Cui
Microvilli are anchored
in the terminal web
Columnar cell
Terminal web
Basement membrane
Microvilli
Connective tissue
Terminal web
CLINICAL CORRELATION
Figure 3-7C.
Celiac (Coeliac) Disease.
Celiac (coeliac) disease
is a disorder of the small
intestine.
Gluten
, a substance found in wheat and bar-
ley, reacts with the lining of the small intestine (small
bowel), leading to an attack by the immune system
and damage to microvilli and villi. If left untreated,
coeliac disease can lead to malabsorption, anemia,
bone disease, and, rarely, some forms of cancer. The
most important treatment is avoidance of all foods that
contain gluten. Histologic features include blunting of
villi, presence of lymphocytes among the epithelial cells
(
intraepithelial lymphocytes
), and
increased lympho-
cytes
within the
lamina propria
(connective tissue).
C
D. Cui
Loss of microvilli
Disrupted terminal web
Columnar cell
Basement membrane
Lymphocyte in lamina propria
Intraepithelial lymphocyte
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