238
UNIT 3
Organ Systems
Urinary Bladder
CLINICAL CORRELATION
Figure 12-14C.
Urothelial (Transitional) Carcinoma.
H&E,
3
108
Urothelial carcinoma
may arise in the urinary bladder,
ureters, or
renal pelvis and is the most common urinary bladder carcinoma.
More than 90% of bladder cancers originate from the transi-
tional epithelium (
urothelium
) in the urinary system. Urothelial
carcinoma is most prevalent in older men but may occur at any
age. Risk factors include
cigarette smoking
, exposure to
arylam-
ines
and
radiation
, long-term use of cyclophosphamide, and
infection by the parasite
Schistosoma haematobium
. Infection
with
S. haematobium
is also a risk factor for the development
of
squamous cell carcinoma
of the urinary bladder. Symptoms
include painless gross hematuria, frequency, urgency, and dysu-
ria. Urothelial carcinomas typically display a papillary morphol-
ogy and are subdivided into low and high grade depending on
cytologic features and the amount of architectural disorder pres-
ent. Treatment includes transurethral resection, chemotherapy,
immunotherapy, and radical cystectomy. Tumors have a high
recurrence rate after local excision.
Papillae in
urothelial
carcinoma
C
Figure 12-14A.
Urinary bladder, bladder wall.
H&E,
3
17;
inset
3
82
The
urinary bladder
has three layers (
mucosa
,
muscularis
, and
adventitia
/
serosa
), similar to those in the ureter, but its wall is
much thicker. Thick mucosa and muscularis layers make up the
wall of the urinary bladder. The
mucosa
is composed of exten-
sively folded
transitional epithelium
and
lamina propria
. This
arrangement gives the bladder the distensibility needed to store
urine. The
muscularis
consists of three
smooth muscle
layers: the
inner longitudinal, middle circular, and outer longitudinal smooth
muscle. These three smooth muscle layers are arranged in two dif-
ferent orientations to help the urinary bladder contract to empty
urine efF
ciently. The outer layer of the bladder is mainly covered
by
adventitia
(connective tissue); its superior (free) surface is cov-
ered by
serosa
, which is a layer of connective tissue with a lining
of
mesothelium
.
Lamina
propria
Muscularis
Muscularis
Muscularis
Smooth muscle
Smooth muscle
Smooth muscle
Submucosa
Submucosa
Submucosa
Epithelium
A
Lamina
Lamina
propria
propria
Lamina
propria
Basal cells
Basal cells
Basal cells
Dome-shaped
surface cells
B
Figure 12-14B.
Urothelium, bladder wall.
H&E,
3
278
This F
gure shows the
urothelium
(transitional epithelium) in a
relaxed state. The urothelial lining of the urinary bladder is thicker
than that of the ureter. The
basal cells
of the urothelium are cuboi-
dal or columnar in shape, the cells in the middle layer of the urothe-
lium are polygonal, and the surface cells are
dome shaped
and
bulge into the lumen when the bladder is empty (relaxed state).
When the bladder is full, the urothelium is stretched, the cells
become fl attened, and the thickness of the urothelium is greatly
reduced (see ±ig. 3-17B).
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