Urinary bladder

Anatomy  ›  Abdomen  ›  Urinary Bladder
Abdomen • Anatomy

URINARY BLADDER

Urinary bladder is a mucomuscular temporary reservoir of urine.

1

Introduction

  • Urinary bladder is a mucomuscular temporary reservoir of urine.
  • It lies in the anterior part of the pelvic cavity.
  • The detrusor muscle of urinary bladder is arranged in whorls and spirals.
  • It is adapted for mass contraction rather than peristalsis.
2

Size, Shape and Position

Size, shape and position of urinary bladder vary according to the amount of urine it contains.

When Empty

  • It lies entirely within the pelvis.

As It Fills

  • It expands.
  • Extends upwards into the abdominal cavity.
  • May reach up to the umbilicus or even higher.

In Children

  • Bladder is an abdominopelvic organ even when empty because of the smaller pelvic cavity.
  • In children, the neck of bladder lies at the level of the upper border of pubic symphysis.
  • Descent of bladder begins after birth and continues up to puberty.
3

Capacity

Mean Capacity

About 220 ml

Range

120–320 ml

  1. Sense of bladder filling first starts at 100–150 ml.
  2. First desire for micturition initiates at 150–250 ml.
  3. Filling beyond 500 ml causes pain due to distention of bladder wall.
Referred Pain

Referred pain is felt in:

  • Lower part of anterior abdominal wall
  • Perineum
  • Penis

Spinal segments → T11–L2; S2–S4

Collection of about 800 ml of urine initiates micturition beyond one’s voluntary control.

4

External Features

Empty Bladder

Empty bladder is tetrahedral in shape.

1. Apex

Directed forwards.

2. Base or Fundus

Directed backwards.

3. Neck

Lowest and most fixed part of bladder.

4. Three Surfaces

  • Superior
  • Right inferolateral
  • Left inferolateral

Four Borders

  • Two lateral
  • One anterior
  • One posterior

Full Bladder

1. Apex

Directed upwards towards the umbilicus.

2. Neck

Directed downwards.

3. Two Surfaces

  • Anterior
  • Posterior

Full bladder is ovoid in shape.

5

Anatomical Position

Hold the cadaveric bladder in such a way that:

  1. Apex is directed upwards and base is directed posteromedially.
  2. Triangular superior surface faces upwards and narrow neck faces downwards.
  3. Convex inferolateral surfaces face inferolaterally.

They face the palm while holding the bladder in hand.

6

Relations of Urinary Bladder

1. Apex

  • Apex is connected to the umbilicus by the median umbilical ligament.
  • Median umbilical ligament represents the obliterated embryonic urachus.

2. Base

Base of urinary bladder is triangular.

It is directed posteroinferiorly.

In Female

  • Related to the uterine cervix and vagina.

In Male

  • Upper part of base: Separated from rectum by the rectovesical pouch and contained coils of intestine.
  • Lower part: Related to seminal vesicles.
  • Related to terminations of vas deferens.
  • Triangular area between the two ductus deferentes is separated from rectum by rectovesical fascia of Denonvilliers.

3. Neck

  • Neck is the lowest and most fixed part of the bladder.
  • Lies 3–4 cm behind the lower part of pubic symphysis.
  • Lies a little above the plane of the pelvic outlet.
  • It is pierced by the internal urethral orifice.

In Male

Neck is surrounded by the prostate.

In Female

  • Neck is related to the pelvic fascia.
  • Pelvic fascia surrounds the upper part of the urethra.

Preprostatic Sphincter Mechanism

  • Smooth muscle bundles surround:
    • Bladder neck
    • Preprostatic urethra
  • These are arranged as a distinct circular preprostatic sphincter.
  • It is devoid of parasympathetic cholinergic nerves.
  • It is part of the proximal urethral sphincter mechanism.

In Infants

  • Bladder lies at a higher level.
  • Internal urethral orifice lies at the level of the superior border of pubic symphysis.
  • It gradually descends to reach the adult position after puberty.

Superior Surface

  • Triangular in shape.
  • Bounded:
    • On each side → lateral borders
    • Posteriorly → posterior border

In Male

  • Completely covered by peritoneum.
  • In contact with:
    • Sigmoid colon
    • Coils of intestine

In Female

  • Peritoneum covers the greater part of superior surface.
  • Exception → small area near posterior border.
  • This area is related to the supravaginal part of uterine cervix.
  • Peritoneum from superior surface is reflected to the isthmus of uterus to form the vesicouterine pouch.

Inferolateral Surfaces

  • Devoid of peritoneum.
  • Separated from each other anteriorly by the anterior border.
  • Separated from superior surface by the lateral borders.

In Male

Each surface is related to:

  1. Pubis
  2. Puboprostatic ligaments
  3. Retropubic fat
  4. Obturator internus muscle
  5. Levator ani muscle

In Female

Relations are the same, except:

  • Puboprostatic ligaments are replaced by pubovesical ligaments.

Space of Retzius / Retropubic Space

  • A perivesical horseshoe-shaped space.
  • Lies between:
    • Anterolateral wall of pelvis
    • Sides of urinary bladder and prostate
  • Allows distension of bladder.

Boundaries

  • Anteriorly → Pubic symphysis and anterior abdominal wall
  • Posteriorly → Inferolateral surface of urinary bladder
  • Superiorly → Peritoneum of paravesical fossa
  • Inferiorly → Puboprostatic or pubovesical ligaments

Contents

  • Retropubic pad of fat
  • Vesical venous plexus
Note
  • As bladder fills, inferolateral surfaces become the anterior surface of the distended bladder.
  • This surface is covered by peritoneum only in its upper part.
  • Lower part comes into direct contact with the anterior abdominal wall without intervening peritoneum.
  • The bladder can be approached surgically through this extraperitoneal route.
  • This route is commonly used for suprapubic cystostomy/catheterisation.
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Ligaments of the Bladder

Ligaments of urinary bladder are classified into:

1. True ligaments

2. False ligaments

True Ligaments

Condensations of pelvic fascia around the neck and base of bladder.

Continuous with the fascia on the superior surface of levator ani.

1. Median Umbilical Ligament

  • Fibrous remnant of the urachus.

2. Medial Puboprostatic Ligaments

  • Right and left.
  • Directed downwards and backwards.
  • Extend from the back of pubic bone near the pubic symphysis to the prostatic sheath.
  • In females, corresponding ligaments are called pubovesical ligaments.
  • They form the floor of the retropubic space.

3. Lateral Puboprostatic Ligaments

  • Right and left.
  • Directed medially and backwards.
  • Extend from the anterior end of the tendinous arch of pelvic fascia to the upper part of the prostatic sheath.

4. Lateral True Ligaments

  • Right and left.
  • Extend from the side of the bladder to the tendinous arch of pelvic fascia.

5. Posterior Ligaments

  • Right and left.
  • Directed backwards and upwards along the vesical plexus of veins.
  • Extend on each side from the bladder to the wall of pelvis.

False Ligaments

These are peritoneal folds which do not form support to the bladder.

  1. Median umbilical fold
  2. Medial umbilical folds — right and left
  3. Lateral false ligaments — right and left
  4. Posterior false ligaments — right and left

Notes

  • Median umbilical fold: Fold of peritoneum covering the median umbilical ligament.
  • Medial umbilical folds: Cover the obliterated umbilical arteries.
  • Lateral false ligaments: Extend from bladder to lateral pelvic wall. Form the floor of paravesical fossae.
  • Posterior false ligaments: Sacrogenital folds. Extend from side of bladder posteriorly to the third sacral vertebra. Lie on either side of rectum.
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Interior of the Bladder

Interior of bladder can be visualized using cystoscopy in living individuals.

1. Vesical Mucosa

  • In an empty bladder:
    • Mucosa shows irregular folds.
    • These folds stretch flat as bladder fills.
    • Mucosa is loosely attached to the underlying muscular layer.
    • Therefore, mucosal folds are visible in an empty bladder.

2. Trigone of Bladder

  • Small triangular area situated on the posteroinferior part of interior of bladder.
  • At the trigone, mucosa is firmly adherent to the muscular wall of bladder.
  • Hence, mucosal folds are not present.

Features of Trigone

  • Anteroinferior angle: Has the internal orifice of urethra.
  • Two posterosuperior angles: Have the openings of ureters.
  • Uvula vesicae: Slight elevation on the trigone immediately posterior to the urethral orifice.
    • Produced by the median lobe of prostate.

3. Interureteric Ridge / Crest

  • Ridge of mucosa extending between the two ureteric orifices.
  • Forms the base of the trigone.
  • Also called bar of Mercier.

4. Ureteric Folds

  • Lateral extensions of interureteric ridges beyond the openings of ureters.
  • Produced by the oblique course of ureters within the bladder wall.

5. Two Uretero-Urethral Ridges (Bell’s Bars)

  • Mucosal folds extending from ureteric orifice to urethral orifice.
  • Produced by the longitudinal fibres of ureter extending downwards.
Embryological Note
  • Trigone of urinary bladder is derived from absorption of mesonephric ducts.
  • Rest of bladder develops from endodermal cloaca.

Ureteric Orifices

  • Slit-like openings.
  • About 2.5 cm apart in empty bladder.
  • About 5 cm apart in distended bladder.
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Arterial Supply

1. Main Supply

Main supply comes from the superior and inferior vesical arteries.

They are branches of the anterior trunk of the internal iliac artery.

2. Additional Supply

  • Obturator artery
  • Inferior gluteal artery

In Females

  • Uterine artery
  • Vaginal artery
  • These are present instead of the inferior vesical artery.
10

Venous Drainage

  • A vesical venous plexus lies on the inferolateral surfaces of the bladder.
  • Veins from this plexus pass backwards in the posterior ligaments of the bladder.
  • They drain into the internal iliac veins.
11

Lymphatic Drainage

  • Most lymphatics from urinary bladder terminate in the external iliac nodes.
  • A few vessels may pass to:
    • Internal iliac nodes
    • Lateral aortic nodes
12

Nerve Supply

Urinary bladder is supplied by the vesical plexus of nerves.

Vesical plexus is made up of fibres derived from the inferior hypogastric plexus.

Fibres Present

  • Sympathetic fibres
  • Parasympathetic fibres
  • Motor/efferent fibres
  • Sensory/afferent fibres

Functional Role

  • Sympathetic innervation → filling of bladder.
  • Parasympathetic innervation → emptying of bladder.
  • Somatic innervation → voluntary control of micturition.

1. Parasympathetic Efferent Fibres

  • Also called nervi erigentes.
  • Spinal segments → S2, S3, S4.
  • Motor to the detrusor muscle.
  • Stimulatory to detrusor muscles.
  • Inhibitory to internal urethral sphincter.

2. Sympathetic Efferent Fibres

  • Spinal segments → T11–L2.
  • Inhibitory to the detrusor.
  • Motor to the preprostatic sphincter mechanism.

3. Somatic Pudendal Nerve

  • Spinal segments → S2–S4.
  • Supplies sphincter urethrae.
  • Sphincter urethrae is voluntary.
  • It is situated within the wall of urethra.

4. Sensory Nerves

  • Pain sensations caused by:
    • Distension of bladder wall
    • Spasms of bladder wall
  • Carried mainly by parasympathetic nerves.
  • Partly carried by sympathetic nerves.
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Clinical Anatomy

1. Cystoscopy

Interior of bladder can be examined in living individuals by cystoscope.

2. Rupture of Distended Bladder

  • A distended bladder may be ruptured by injuries to the lower abdominal wall.
  • Peritoneum may or may not be involved.

3. Chronic Obstruction to the Outflow of Urine

  • Chronic obstruction to the outflow of urine by an enlarged prostate causes hypertrophy of bladder.
  • This leads to a trabeculated bladder.

4. Suprapubic Cystotomy or Catheterisation

  • Bladder is distended with about 300 ml of fluid.
  • As a result, the anterior aspect of bladder comes into direct contact with the anterior abdominal wall.
  • It can be approached without entering the peritoneal cavity.

5. Urinary Stone Formation

Urinary bladder is one of the sites for urinary stone formation because concentrated urine lies here.

URINARY BLADDER
Anatomy study notes.