CHAPTER 12
Urinary System
237
Figure 12-13A.
Ureter.
H&E,
3
61
The
ureter
is a small muscular tubule lined with transitional
epithelium. It carries urine from the renal pelvis to the
urinary
bladder. The wall of the ureter is composed of
mucosa
,
muscularis
, and
adventitia
. The
mucosa
consists of transitional
epithelium and loose connective tissue (
lamina propria
). The
middle layer, the
muscularis
, is relatively thick and contains
inner longitudinal and outer circular smooth muscle layers.
These two muscle layers are often difF
cult to distinguish. The
wall of the ureter becomes thicker as it nears the bladder. As
it approaches the urinary bladder, the ureter may also contain
a third layer of smooth muscle. The
adventitia
layer is com-
posed of connective tissues, nerve F
bers, and blood vessels. It
provides protection, blood supply, and nervous innervation
to the ureter.
Muscularis
Muscularis
Muscularis
Adventitia
Epithelium
Epithelium
Epithelium
Lamina
Lamina
propria
propria
Lamina
propria
Mucosa
Mucosa
Mucosa
A
CLINICAL CORRELATION
Figure 12-13C.
Nephrolithiasis (Renal Stones).
Nephrolithiasis
(
renal stones
) is common in clinical practice.
Symptoms range from vague abdominal pain to renal colic
and hematuria when stones pass from the renal pelvis into the
narrow portion of the ureter. Most renal stones are composed of
the
calcium salts, calcium oxalate, or calcium phosphate. Other
less common forms include uric acid, magnesium ammonium
phosphate (struvite), and cystine stones. Risk factors for the
development of kidney stones include dietary factors, metabolic
abnormalities, abnormal urine pH, family history of renal stones,
frequent upper urinary tract infections, and low fl
uid intake.
Struvite stones are associated with urinary tract infection with
urea-splitting bacteria such as
Proteus
species. Treatment varies
based upon the location and size of the stones and includes
analgesics, shock wave lithotripsy, ureteroscopy, and surgery.
D. Cui
&T. Yang
Stone
in kidney
Stone
in ureter
Kidney
Ureter
Bladder
Urethra
Stone
in bladder
C
Ureters
Transitional
Transitional
epithelium
epithelium
Transitional
epithelium
Luman
Luman
Lumen
Lamina propria
Lamina propria
(connective tissue)
(connective tissue)
Lamina propria
(connective tissue)
B
Figure 12-13B.
Transitional epithelium, ureter.
H&E,
3
190
Transitional epithelium
lines the urinary tract from the
urinary calyces to the bladder. This type of epithelium can
change shape as it is stretched to accommodate a change in
volume. Cells on the surface layer appear round and dome
shaped when the bladder is in a relaxed state. These cells
become fl
attened and the layers of cells are reduced in number
when the epithelium is stretched. The transitional epithelium
lining the urinary tract is also called
urothelium
; it has tight
junctions and thick cytoplasm (±igs. 12-14B and 12-15A,B).
The
lumen
of the ureter appears as a white space here.
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