801
CHAPTER TWENTY
Urinary System
mucous glands, called
urethral glands,
which secrete mucus
into the urethral canal
(f
g. 20.31)
.
In a female, the urethra is about 4 centimeters long. It
passes forward from the bladder, courses below the symphy-
sis pubis, and empties between the labia minora. Its open-
ing, the
external urethral orif
ce
(urinary meatus), is anterior
to the vaginal opening and is about 2.5 centimeters posterior
to the clitoris
(f g. 20.32
a
)
.
In a male, the urethra, which functions both as a urinary
canal and a passageway for cells and secretions from the
reproductive organs, can be divided into three sections: the
prostatic urethra, the membranous urethra, and the penile
urethra (see F
g. 20.32
b
and reference plate 20).
The
prostatic urethra
is about 2.5 centimeters long and
passes from the urinary bladder through the
prostate gland,
located just below the bladder. Ducts from reproductive
structures join the urethra in this region.
FIGURE 20.30
Light micrograph of the human urinary bladder
wall (6×).
FIGURE 20.31
Cross section through the urethra (10×).
FIGURE 20.32
Urinary bladder and urethra (
a
) of the female
(longitudinal section) and (
b
) of the male (longitudinal section).
Muscular coat
Mucous coat
Lumen
Lumen
Submucous
coat
Urethral glands
Muscle layer
Lumen of urethra
Mucous membrane
External
urethral orifice
Urethra
External
urethral orifice
Trigone
Prostatic
urethra
Membranous
urethra
Penile
urethra
Ureter
Urinary
bladder
Trigone
Ureter
Urinary
bladder
Prostate
gland
Bulbourethral
gland
Penis
(a)
(b)
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