240
UNIT 3
Organ Systems
Prostatic
Prostatic
urethra
urethra
Prostatic
urethra
Ejaculatory
Ejaculatory
duct
duct
Ejaculatory
duct
Prostatic glands
Prostatic glands
with concretions
with concretions
Prostatic glands
with concretions
Ejaculatory
Ejaculatory
duct
duct
Ejaculatory
duct
A
Figure 12-16A.
Prostatic urethra, male urethra.
H&E,
3
17
The
urethra
provides for the passage of urine from the bladder to
the outside of the body. The male urethra is signiF cantly different
from that of the female. It is a long tube (18–20 cm), which passes
through the prostate and penis. The male urethra can be divided
into three parts:
prostatic, membranous
, and
penile
(
spongy
) based
on its anatomical location. This F
gure shows a cross section of the
prostatic urethra
connecting to two
ejaculatory ducts
, surrounded
by the prostate. The
prostatic urethra
is a short segment (3–4 cm),
usually lined by transitional epithelium. This portion of the ure-
thra is surrounded by prostatic glands. The
membranous urethra
is narrow and short (1–2 cm) and passes through the deep perineal
pouch. It is lined by pseudostratiF
ed columnar epithelium and sur-
rounded by an inner longitudinal smooth muscle and an outer skel-
etal muscle of the external urethral sphincter. The
penile
(
spongy
)
urethra
is the longest segment (12–14 cm).
Submucosal
Submucosal
glands of Littré
glands of Littré
Submucosal
glands of Littré
Erectile tissue of the
Erectile tissue of the
corpus spongiosum
corpus spongiosum
Erectile tissue of the
corpus spongiosum
Urethra
Urethra
Urethra
Submucosal
Submucosal
glands of Littré
glands of Littré
Submucosal
glands of Littré
Urethra
Urethra
Urethra
Corpus spongiosum
Corpus spongiosum
Corpus spongiosum
Corpora cavernosum
Corpora cavernosum
Corpora cavernosum
B
Figure 12-16B.
Penile (spongy) urethra, male urethra.
H&E,
3
34;
inset
3
6 (
upper
),
3
170 (
lower
)
The
penile urethra
is also called the
spongy urethra
because it passes
through the penis and is surrounded by
erectile tissue
(
corpus spon-
giosum
). The terms “cavernous” or “bulbous” urethra may also be
used to refer to the penile urethra. The penile urethra is lined by
pseudostratiF
ed columnar epithelium. Close to the tip of the penis,
the lining becomes stratiF
ed squamous epithelium. This view shows
the urethra in the corpus spongiosum, surrounded by spongy erec-
tile tissue. Within the lining of pseudostratiF
ed columnar epithe-
lium are clusters of mucus-secreting cells, the
glands of Littré
. The
glands of Littré located in the epithelium are called
intraepithelial
glands of Littré
; similar glands found in the submucosa are termed
submucosal
or
extraepithelial glands of Littré
. The secretions of the
mucous cells of these glands protect the urethra from the effects of
the urine. The
upper left inset
shows the urethra associated with the
corpus spongiosum and corpora cavernosa in the penis.
Intraepithelial
Intraepithelial
glands of Littré
glands of Littré
Intraepithelial
glands of Littré
Stratified
Stratified
squamous
squamous
epithelium
epithelium
Stratified
squamous
epithelium
Intraepithelial
Intraepithelial
glands of Littré
glands of Littré
Intraepithelial
glands of Littré
Intraepithelial
Intraepithelial
glands of Littré
glands of Littré
Intraepithelial
glands of Littré
Smooth muscle
Smooth muscle
Smooth muscle
Urethra
Urethra
Urethra
C
Figure 12-16C.
Urethra, female urethra.
H&E,
3
34; inset
3
177
The
female urethra
is 4 to 5 cm long, much shorter than the male
urethra. It conveys urine from the urinary bladder, passing inferi-
orly through the pelvic fl
oor and exiting anterior/superior to the
vaginal opening in the vestibule. The female urethra is initially
lined by pseudostratiF
ed columnar epithelium, which changes to
strati±
ed squamous epithelium
as it approaches the external open-
ing of the urethra. It has a thick lamina propria with many elastic
F bers and venous plexi. The
glands of Littré
are also present in
the female urethra. Its wall is surrounded by longitudinal
smooth
muscle
. The middle portion of the wall of the urethra is surrounded
by the outer layer of the
external urethral sphincter
, which has the
same function as in the male urethra.
Urethra
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