The Urinary Bladder and Urethrae
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The suprarenal glands
| Main Anatomy Index | Female internal gentialia
Last updated 30 March 2006
The Urinary Bladder
- The bladder (L. vesica) is a hollow, muscular vesicle for storing urine.
- In adults, the empty bladder lies in the pelvis minor.
- It lies posterior and slightly
superior to the pubic bones.
- It is separated from the pubic bones by the retropubic space.
- As the bladder fills, it ascends into the pelvis major and a very full bladder may ascend to the
level of the umbilicus.
- The bladder is a hollow viscus with strong
- It is characterised by its distensibility.
- Its shape, size, position, and relations are
dependent with the amount of urine it contains and with
the age of the person.
- The mucous membrane is loosely
connected to its muscular wall, except in a triangular region in its base
- This region is known as the trigone of the bladder.
- The mucous membrane in the empty bladder is in numerous
folds or rugae except in
the trigone area where it is always smooth (due it its
firm attachment to the muscular wall).
The Form of the Bladder
Click here for a schematic of the shape of the
- The shape of the bladder in cadavers is like a tetrahedron
(it is more or less rounded in living persons).
- It has 4 sides, 4 angles and 4 ducts.
The Sides of the Bladder
- The base or fundus, which is related to the anterior vaginal wall (females) or the rectum, seminal vesicles
and ductus deferens (males);
- The superior surface;
- And 2 inferolateral surfaces, which is separated from
the pubis and puboprostatic
ligament (male) or pubovesical ligament
(female) by the retropubic fat pad.
The Angles of the Bladder
- The apex, which is continuous with the obliterated urachus (median umbilical ligament);
- The neck, which is the most inferior part and is
related to the prostate (males) or superior
pelvic fascia (females);
- And 2 lateral angles where the ureters enter the bladder.
The Ducts of the Bladder
- The urachus from the apex;
- The 2 ureters
from the lateral angles;
- And the urethra, which pierces the neck
of the bladder.
- Bladder capacities in the adult male vary from 120 mL to 320 mL, with
micturition usually occurring at 280 mL (Ashwell).
- When the bladder is filled it contains about 500 mL (Moore).
- Values for females are presumably less.
The Bladder Bed
- The shape of the bladder is largely determined by the structures that are closely related to it.
- The entire organ is enveloped by loose connective tissue,
called vesicle fascia, in which is located the vesical venous plexus.
- The bladder bed is formed by:
- On each side by the pubic bones;
- The levator ani muscles;
- The obturator internus muscle;
- And posterior by the rectum.
- In the female the base of the bladder is separated from the rectum
by the cervix and the superior part
of the vagina.
- The bladder neck lies directly on
the pelvic fascia, surrounding the short urethra.
- In the male, the base of the bladder is separated from the rectum
by the ampullae of the ductus
deferens and the seminal vesicles.
- Its neck fuses with the prostate.
The Ligaments of the
- In both sexes, there are ligaments that extend from the
posterior of the pubis
to the neck of the bladder.
- These are the pubovesicle ligaments.
- These are the superior extensions of the pubourethral ligaments (female) and the puboprostatic
- These ligaments lie on either side of the midline and the small space between them is
for the transmission of small veins.
- Lateral and posterior ligaments
are described as reflections of peritoneum.
- They are considered as false ligaments by some authors.
- The bladder apex is also connected to the umbilicus by the urachus (the
median umbilical ligament).
The Interior of the Bladder
Click here for a diagram of the interior of the
- The trigone, which is a smooth
area on the interior of the base,
is bounded by the internal ureteric
orifices (2.5 cm apart in the empty bladder)
and the internal urethral orifice.
- The internal ureteric orifices are joined
by the interureteric ridge (or crest).
- These ridges may extend past the ureteric openings laterally as the ureteric
- In adult males, particularly past middle age, there is
a slight elevation of the mucosa posterior to the internal urethral orifice.
- This is known as the uvula and is formed by the median prostatic lobe.
- In men with an enlarged prostate gland, this uvula may
obstruct the internal urethral orifice.
Supply of the Urinary Bladder
- The superior vesicle artery, branches of the umbilical artery supply the anterosuperior
parts of the bladder.
- The inferior vesicle arteries (in males) or vaginal arteries (in females), branches of the internal iliac arteries, supply the base
of the bladder.
- The obturator and inferior
gluteal arteries also supply small branches to the bladder.
Drainage of the Urinary Bladder
- The veins from a venous plexus on the inferolateral surface and drain back to the internal
Lymphatic Drainage of the Urinary Bladder
- The lymph vessels from the superior part of the bladder
pass to the external iliac lymph nodes.
- Those from the inferior part of the bladder pass the internal iliac lymph nodes.
- Some lymph vessels from the neck region of the bladder drain into the sacral
or common iliac lymph nodes.
the Urinary Bladder
The Efferent Fibres
- Parasympathetic from the S2-4
segments of the spinal cord (nervi erigentes).
- These enter the inferior hypogastric plexus and pass
through it to the bladder wall.
- They are motor to the detrusor and inhibitory
to the internal sphincter.
- Sympathetic from the T11-12,
L1-2 segments of the spinal cord.
- These synapse in the inferior hypogastric plexus and
the postganglionic fibres pass to the bladder.
- They cause constriction in the internal
sphincter and inhibit the detrusor
The Afferent Fibres
- These are concerned with the awareness of distension and pain.
- They pass back to the CNS via both the sympathetic and parasympathetic nerves.
The Male Urethra
- In the male, the urethra is about 18-20
cm long and it extends from the internal urethral orifice
in the bladder to the external
meatus on the tip of the penis.
The Preprostatic Part
- This part possesses a stellate lumen and is only 1.5 cm long.
- It extends from the internal urethral orifice to the superior aspect of the prostate.
- Smooth muscle surrounding the bladder neck and preprostatic urethra is circular
and is known as the internal sphincter (sphincter
- This is richly supplied with sympathetic
The Prostatic Part
- This is 3-4 cm long and has a midline
ridge on its posterior wall known as the urethral crest.
- On each side of the crest is a groove known as the prostatic sinus, into which the orifices of the prostatic ducts open.
- There is an elevation on the urethral
crest about halfway down which is known as the collicus
- On the summit of this, the prostatic utricle opens.
- The prostatic utricle is 6 mm
long and is the remnant of the paramesonephric ducts.
- On either side of the utricle are the openings of the ejaculatory ducts.
The Membranous Part
- The sphincter urethrae is supplied by the perineal branches
of the pudendal nerve (S2-4).
The Spongiose Part
- This part is contained within the corpus spongiosum of
- It is dilated at its beginning as the intrabulbar fossa,
and again within the glans of the penis as the navicular fossa.
- The ducts of the bulbourethral
gland opens into the spongiose part below the perineal membrane.
- The external urethral orifice is the narrowest part of
- There are several recesses in the urethra
known as lacunae.
- Mucous glands known as urethral glands open into this
part of the urethra.
The Female Urethra
- The female urethra is only 4 cm long and opens at the external urethral orifice.
- This is about 2.5 cm behind the glans
clitoris and directly in front of the vaginal opening.
- The female urethra has a posterior longitudinal fold
(as known as the urethra crest).
- Similarly, it also has external and internal
The Stages of Micturition
- Pubovaginalis (female) and levator
prostatae (male), parts of the pubococcygeus
- The bladder neck drops;
- The downward movement initiates contraction
of the detrusor and relaxation
of the sphincter vesicae (parasympathetic reflex arcs);
- Somatic nerves (S2-4) relax the external urethral sphincters;
- The urine passes outwards.