CHAPTER 15
Digestive Tract
287
Submucosa
Submucosa
Submucosa
Submucosa
Submucosa
Submucosa
Lamina
Lamina
propria
propria
Lamina
propria
Esophageal
Esophageal
cardiac glands
cardiac glands
Esophageal
cardiac glands
epithelium
epithelium
epithelium
Mucosa
Mucosa
Mucosa
Simple
Simple
columnar epithelium
columnar epithelium
Simple
columnar epithelium
Stratified squamous
Stratified squamous
epithelium
epithelium
Stratified squamous
epithelium
Muscularis
Muscularis
externa
externa
Muscularis
externa
Mucosa
Mucosa
Mucosa
A
Figure 15-5A.
Lower esophagus, esophagogastric junction
(
esophagus on
left
; stomach on
right
of
illustration
).
H&E,
3
11;
insets (
upper
)
3
57; (
lower
)
3
45
The
lower esophagus
meets the stomach at the
esophagogastric
junction
.
The esophagus is lined by stratiF ed squamous epithelium, and the car-
diac region of the stomach is lined by simple columnar epithelium. The
change in the lining epithelium refl ects the change in function from a
conduit for food transport to an organ of digestion. The muscularis
externa of the lower esophagus is composed of two layers of smooth
muscle F bers, which are controlled by the vagus nerve. Mucous glands
are also found in the lamina propria of the lower esophagus (
right
inset
). These glands are called
esophageal cardiac glands
. They pro-
duce mucus to protect the epithelial wall of the esophagus from the
refl ux of acidic gastric juices coming from the stomach.
In some patients, the epithelium of the lower esophagus (stratiF ed
squamous epithelium) changes to stomachlike epithelium (simple
columnar epithelium). This pathologic change is called
metaplasia
.
It is due to the long-term chemical irritation caused by
gastroesopha-
geal refl ux
.
CLINICAL CORRELATIONS
Figure 15-5B.
Barrett Esophagus
. H&E,
3
48; inset
3
82
Barrett esophagus
is a chronic complication of
gastroesophageal
refl
ux disease (GERD)
, characterized by
metaplasia
of the strati-
F ed squamous epithelium of the lower esophagus into a special-
ized
glandular epithelium with goblet cells
. Patients with Barrett
esophagus have an increased risk of developing
adenocarcinoma
(cancer of the esophagus) of the distal esophagus. Common symp-
toms include heartburn, trouble swallowing, and weight loss.
Endoscopically, Barrett esophagus appears as salmon-colored
“tongues” of mucosa extending proximally from the gastroe-
sophageal junction. This photomicrograph shows the
metaplastic
glandular epithelium
with
goblet cells
that have replaced the
normal squamous epithelium and the infl ammatory cells (mainly
lymphocytes and plasma cells) inF ltrating the connective tissue.
Figure 15-5C.
Esophageal Carcinoma.
H&E,
3
97
Esophageal carcinoma
is a
malignant neoplasm
that stems
from the epithelial cells lining the inner surface of the esopha-
gus. Worldwide,
squamous cell carcinoma
is the most common
type of esophageal cancer, and it is associated with alcohol and
tobacco use in the United States and Europe and with mutagenic
substances and nutritional deF
ciencies in less-well-developed
parts of the world. In the United States,
adenocarcinoma
of the
lower esophagus is becoming more frequent, representing about
50% of esophageal cancers. The major known risk factor for
the development of adenocarcinoma is
chronic GERD
causing
Barrett esophagus
, a
metaplastic
change in the squamous mucosa
of the distal esophagus to a glandular type of epithelium with
goblet cells. Esophageal cancer is characterized by progressive
difF
culty in swallowing, loss of weight, fatigue, and chest pain.
Pathological changes include
ulcerations
,
exophytic masses
, and
thickening and narrowing of the lumen. Treatment includes sur-
gery (
esophagectomy
) and chemotherapy. This photomicrograph
shows a moderately differentiated squamous cell carcinoma with
focal keratin production in the center, called a
keratin pearl
.
Metaplastic
Barrett
epithelium with
goblet cells
Squamous
epithelium
Goblet cell
B
Keratin pearl
Squamous cell
carcinoma
C
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