Urinary Bladder and Urethra - Female
This page continues from the general description
of the human bladder.
The female bladder and urethra is shown in the following
diagram and the parts labelled in the diagram are explained
Diagram of the Female Bladder and Urethra
* Ureter (x2)
* Detrusor muscle
* Ureter orifices
* Neck of bladder
* Urethral sphincter
* Urogenital diaphragm
* External urethral sphincter
Quick Re-cap from previous pages:
- The urinary bladder stores urine prior to its elimination
from the body (functions
of the urinary system).
At micturation/urination, the bladder expels urine
into the urethra, leading to the exterior of the body.
is a musculomembranous sac located on the floor of
the pelvic cavity, anterior to the uterus and upper
vagnia (in females).
- Outer surfaces of the Bladder: The upper
and side surfaces of the bladder are covered by peritoneum
(also called "serosa"). This serous membrane
of the abdominal cavity consists of mesthelium and
elastic fibrous connective tissue. "Visceral
peritoneum" covers the bladder
and other abdominal organs, while "parietal
peritoneum" lines the abdomen walls.
- Ureters: The ureters deliver urine to the
bladder from the kidneys
(one ureter from each kidney - see components
of human urinary system). The ureters pass through
the posterior surface of the bladder at the Ureter
Orifices (shown above). Urine drains through
the ureters directly into the bladder as there are
no sphincter muscles or valves at the ureter orifices.
- Structure of Bladder (Detail): The bladder
itself consists of 4 layers:- (1) Serous
- this outer layer being a partial layer derived from
the peritoneum, (2) Muscular
- the detrusor muscle of the urinary
bladder wall, which consists of 3 layers incl. both
longitudinal and circularly arranged muscle
fibres, (3) Sub-mucous
- a thin layer of areolar tissue loosely
connecting the muscular layer with the mucous layer,
and (4) Mucous
- the innermost layer of the wall of the urinary bladder
loosely attached to the (strong and substantial) muscular
layer. The mucosa falls into many folds known as rugae
when the bladder is empty or near empty.
- The features observable on the inside of the bladder
are the ureter orifices, the trigone,
and the internal orifice of the urethra.
- The trigone is a smooth triangular
region between the openings of the two ureters and
the urethra and never presents any rugae even when
the bladder is empty - because this area is more tightly
bound to its outer layer of bladder tissue.
- Exit from Bladder: When urine is released
from the bladder is flows out via the neck
of the bladder (in the trigone region).
The internal urethral sphincter is
a sphincter (circular) muscle located at the neck
of the bladder and formed from a thickening of the
detrusor muscle. It closes the urethra when the bladder
- More detail about the above is included on the
page about the bladder.
The female urethra
At only about 1.5 inches (35 mm) long,
the female adult urethra is shorter than the adult male
urethra (approx. or 8 inches, or 200mm). The female
urethra is located immediately behind (posterior to)
the pubic symphysis and is embedded into the front wall
of the vagina.
The urethra itself is a narrow membranous canal that
consists of three layers:
- Muscular layer
- continuous with the muscular layer of the bladder,
this extends the full length of the urethra.
- Thin layer of spongy
- including plexus of veins and bundles of smooth
muscle fibres. Located immediately below the mucous
- Mucous layer
- internally continuous with the bladder and lined
with laminated epithelium that is transitional near
to the bladder.
After passing through the urogenital diaphragm
(as shown in the diagram), the female urethra ends at
the external orifice of urethra - which
is the point at which the urine leaves the body. This
is located between the clitoris and the vaginal opening.
The passage of urine along the urethra through the
urogenital diaphragm is controlled by the external
urethral sphincter, which is a circular muscle
under voluntary control (that is, it is innervated
by the somatic nervous system, SNS). See the page
about micturation for more about control of these structures
by the nervous system.
The female urethra is a much simpler structure than
the male urethra because it carries only urine (whereas
the male urethra also serves as a duct for the ejaculation
of semen - as part of its reproductive function).
Next: Also see
the diagram of the male
bladder and urethra.
Then review the process of micturation and the composition