Urinary Bladder and Urethra - Male
This page continues from the general description
of the human bladder.
The male bladder and urethra is shown in the following
diagram and the parts labeled in the diagram are explained
Diagram of the Male Bladder and Urethra
* Ureter (x2)
* Detrusor muscle
* Ureter orifices
* Neck of bladder
* Urethral sphincter
* Urogenital diaphragm
* Internal urethral sphincter
* Prostatic Urethra
* Membranous Urethra
* Spongy Urethra
* External Urethral sphincter
Labeled components that are not part of
the urinary system:
* Cowper's Gland
* Glans Penis
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
vagina (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 male urethra
At about 8-9 inches (200 mm) long, the
adult male urethra is longer than the
urethra (of approx. 1.5 inches 35 mm). It has three
portions (the prostatic urethra,
the membranous urethra, and
the spongy urethra - see below)
and extends from the neck of the bladder (shown in the
diagram above) to the meatus urinarius
at the end of the male penis/urethra.
The general shape of the urethra (the tube itself)
varies along it's length: The prostatic section of the
male urethra is somewhat arched. Except during passage
of urine or semen through the urethra, it is a transverse
slit along it's length, the upper and lower surfaces
of the transverse slit being in contact when fluid is
not passing along the urethra. However, at exit from
the body at the meatus urinarius (external
orifice of urethra) the slit is vertical.
The three regions/sections of the male urethra are:
- Prostatic Urethra
The prostatic urethra begins at the
neck of the bladder and includes
all of the section that passes through the prostrate
gland. It is the widest and most dilatable
part of the male urethral canal.
- Membranous Urethra
The membranous urethra is the shortest
and narrowest part of the male urethra. This section
measures approx. 0.5 - 0.75 inches (12 - 19 mm) in
length and is the section of the urethra that passes
through the male urogenital diaphragm.
The external urethral sphincter (muscle)
is located in the urogenital diaphragm (as for the
female urethra). This muscle is referred to as
the "compressor urethrae muscle" in some
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.
- Spongy Urethra
The spongy urethra is the longest
of the three sections. It is approx. 6 inches (150
mm) in length and is contained in the corpus spongiosum
that extends from the end of the membranous portion,
passes through the penis, and terminates
at the external orifice of the urethra
- which is the point at which the urine leaves the
Structure of the Male Urethra
The structure of the urethra (tube) itself is a continuous
mucous membrane supported by submucous
tissue connecting it to the other structures
through which it passes.
- The mucous coat is continuous
with the mucous membrane of the bladder, ureters and
kidney. In the membranous and spongy sections (2.
and 3. above), the mucous membrane is arranged in
longitudinal folds when the tube is empty.
- The submucous tissue consists
of a vascular (i.e. containing many blood vessels)
erectile layer surrounded by a layer of smooth (involuntary)
fibres. These muscle fibres are arranged in a
circular configuration that separates the mucous membrane
and submucous tissue from the surrounding structure
- which is the tissue of the corpus spongiosum (labeled
simply "penis" in the diagram above).
Unlike the female urethra, the male urethra has a reproductive
function in addition to it's urinary function - it conveys
semen out of the body at ejaculation. For further information
about this function red the section about the male reproductive
Next: Also see
the diagram of the female
bladder and urethra.
Then review the process of micturation and the composition