292
UNIT 3
Organ Systems
CLINICAL CORRELATION
Figure 15-10C.
Peptic Duodenitis.
H&E,
3
48
Peptic duodenitis
is an infl
ammatory process caused by chronic
exposure of the
duodenal mucosa
to increased levels of gastric
acid and is usually found in the F rst portion of the duodenum, the
duodenal bulb
. Symptoms of peptic duodenitis include epigas-
tric pain and
dyspepsia
. Histologic features include fl attening, or
blunting, of the normally F ngerlike villi,
increased infl ammatory
cells
within the lamina propria,
Brunner gland hyperplasia
,
crypt
hyperplasia
, and
gastric foveolar metaplasia of the epithelium
.
Metaplasia to a gastric foveolar type of epithelium is an adaptive
protective response to the increased levels of acid.
H. pylori
may
be found in the metaplastic mucosa as seen in the stomach. In
time, a duodenal ulcer may result from peptic duodenitis. This
photomicrograph shows duodenal mucosa with complete replace-
ment of the normal epithelium with goblet cells by
gastric foveo-
lar epithelium
. Note the widened, distorted villi and increased
infl ammatory cells
within the
lamina propria
.
Metaplastic
gastric mucosa
with loss of
goblet cells
Blunt, widened
villous with
inflammation
C
Figure 15-10A.
Duodenum, small intestine.
H&E,
3
14
The
duodenum
connects to the stomach. The
mucosa
of the duode-
num is composed of
simple columnar epithelium
,
lamina
propria
,
and
muscularis mucosae
.
Epithelial cells
lining the surface of the villi
and the
glands of Lieberkühn
include absorptive cells, goblet cells,
Paneth cells, enteroendocrine cells, and stem cells. The
lamina pro-
pria
is a layer of loose connective tissue, which forms the core of the
villus and contains various types of connective tissue cells includ-
ing F broblasts, plasma cells, macrophages, and some leukocytes
(see ±ig. 4-3A). The
muscularis mucosae
is a thin layer of smooth
muscle (±ig. 15-10B). The
submucosa
is a layer of dense connec-
tive tissue containing mucous glands called
Brunner glands
, which
produce mucus to protect the duodenal wall from acidic gastric juice
from the stomach. The
muscularis externa
consists of two layers of
smooth muscle: an inner circular layer and an outer longitudinal
layer. The outer layer of the duodenum is mostly covered by serosa;
areas where it is attached to other organs are covered by adventitia.
Villi
Villi
Villi
Glands of
Glands of
Lieberkühn
Lieberkühn
Glands of
Lieberkühn
Submucosa
Submucosa
Submucosa
Mucosa
Mucosa
Mucosa
Brunner
Brunner
gland
gland
Brunner
gland
Muscularis
Muscularis
externa
externa
Muscularis
externa
A
Figure 15-10B.
Duodenum, small intestine.
H&E,
3
45; inset
3
112
An example of the
mucosa
and
submucosa
of the
duodenum
is
shown. A thin layer of
muscularis mucosae
lies between the lamina
propria and the submucosa. ±ingerlike
villi
project into the lumen
(±ig. 15-11B).
Brunner glands
are distributed in the submucosa
and extend into the lamina propria of the mucosa. Brunner glands
produce mucus that protects the epithelium from
HCl
secreted in
the stomach. They also secrete large numbers of
bicarbonate ions
,
which neutralize acidic gastric juice from the stomach. Two types
of
enteroendocrine cells
associated with the regulation of gastric
secretion are also found in the glands of Lieberkühn of the duode-
num: (1)
G cells
that release
gastrin
, which stimulates parietal cell
secretion of HCl and (2)
D cells
that release
somatostatin
, which
inhibits gastrin release. G cells and D cells are predominantly found
in the pylorus of the stomach but are also found in the duodenum.
L
u
m
e
n
Lumen
Glands of
Glands of
Lieberkühn
Lieberkühn
Villi
Villi
Glands of
Lieberkühn
Villi
Brunner
Brunner
glands
glands
Brunner
glands
Muscularis
Muscularis
mucosae
mucosae
Muscularis
mucosae
Submucosa
Submucosa
Submucosa
Brunner
Brunner
glands
glands
Brunner
glands
Brunner
Brunner
glands
glands
Brunner
glands
B
If Brunner cells are not able to produce enough mucus and bicar-
bonate ions over the long term, a
duodenal
(
Brunner
)
ulcer
may
develop.
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