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Urinary Bladder

  1. Urinary bladder is a hollow viscous and acts as reservoir of urine. When empty, it is tetrahedral in shape and is totally a pelvic organ. When distended, it becomes abdomino-pelvic organ and ovoid in shape. The average capacity varies between 120-320 ml, with mean capacity being about 220 ml. Sense of filling of bladder first starts at filling of 100-150 mI.First desire for micturition usually appears at 150-250 ml filling. Painful sensations start when amount of urine reaches above 450 ml. On collection of about 800 ml the micturition is beyond voluntary control.
  2. Empty bladder has an apex, a base, a neck, a superior surface, two inferolateral surfaces and four borders (anterior, posterior and two laterals).
  3. Apex is connected to umblicus by median umbilical ligament (obliterated embryonic urachus).

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  1. Base (posteriorsurface or fundus) is related to cervix and vagina in females. In males, the upper part of base is separated from the rectum by rectovesical pouch and lower part is related to the seminal vesicles and ampulla of vas deferens. The triangular area between two ductus deferens is separated from the rectum by the rectovesical fascia of Denonvilliers.
  2. Neck is the lowest and most fixed part and lies 3-4 cm behind the lower part of pubic symphysis.
  3. Superior surface is covered with peritoneum and is related to sigmoid colon, coils of small intestine and in female uterus.
  4. Inferolateral surface is devoid of peritoneum and is related to pubis, puboprostatic ligament (or in females pubocervical ligament), retropubic fat, levator ani and obturator internus. These structures are separated from bladder by a space, cave of Retziuswhich intervenes between the antero-lateral pelvic wall and the sides of the bladder and prostate. This space contains retropubic fat and vesical venous plexus. The space acts as a bursa to allow distension of bladder.

Interior of bladder and wall of bladder


Lining epithelium of bladder mucosa is transitional epithelium. When empty mucosa is thrown into rugae except in trigone, where mucosa is smooth and firmly adherent. Ureters open at the lateral angles of the trigone and internal urethral orifice lies at the apex. Interureteric ridge (Mercier's bar) forms the base of trigone (line joining two ureteric orifices). Distance between ureteric orifices is 2.5 cm when empty and 5 cm when bladder is distended. In males, there is a bulging immediately posterior to the urethral orifice produced by median lobe of prostate, is called the vulva vesicae. Just beneath the mucosa of trigone there is layer of smooth muscle, Trigonal muscle of Bell which replaces the submucous coat in trigone area.


Deep to the mucosa, there is submucosa (submucosal coat) except in the region of trigone, where submucosal coat is replaced by, smooth muscle layer (trigonal muscle of Bell). Deep to submucosal coat, there is muscular coat caIIed detrusor muscle. In the region of trigone, muscular coat (detrusor muscle) is separated from trigonal muscle of Bellby fascia of Waldeyer.

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Arterial supply and lymphatic drainage

  1. Arterial supply is through superior vesical artery and in males inferior vesical artery (both are branches of anterior trunk of internal iliac artery). Additional supply comes from obturator artery, inferior gluteal artery, and in females uterine and vaginal arteries.
  2. Most of the lymphatics from the urinary bladder drain into external iliac nodes. A few lymphatics may drain into internal iliac or lateral aortic (para-aortic) nodes.

Nerve supply


Bladder is supplied by both sympathetic and parasympathetic fibers.

  1. Parasympathetic: Preganglionic fibers arise from S2 to S4 cord segments, pass via pelvic splanchnic nerves. After relay in ganglion cells in pelvic plexus (inferior hypogastric plexus) and in bladder wall, postganglionic fibers supply detrusor muscle. Contraction of detrusor muscle is mediated by cholinergic muscarinic receptors. Preganglionic parasympathetic neurons at S2, S3, and S4 cord segments innervating bladder form sacral micturition center.
  2. Sympathetic: Preganglionoic fibers arise from lateral horn cells of T11-L2 cord segments and pass via lower lumbar splanchnic nerves, superior hypogastric plexus (presacral nerve of Latarjet) to reach inferior hypogastric (pelvic) plexus. After relay in pelvic ganglia, postganglionic sympathetic fibers (i) stimulate sphincter vesicae (internal
    1. Referred pain is felt in lower part of anterior abdominal wall (hypogastrium), upper part of front of thigh, scrotum or labium majus, penis or clitoris, and perineum. Centrally, spinothalamic pathway conducts pain impulses from bladder,
    2. Stretch afferents: arising from stretch receptors in the bladder wall pass via pelvic splanchnic nerves, enter S2' S3 and S4 cord segments and establish reflex connections with sacral micturition center, which innervates detrusor. So afferent and efferent limb of this micturition reflex is formed by pelvic splanchnic nerves .Sacral micturition center and the micturition reflex are controlled by facilitatory and inhibitory centers located in pons and paracentral lobule of frontal lobe of cerebrum.

Male Urethra

It is 18-20 cm long.1t extends from internal urethral orifice at the apex of trigone of bladder to external urethral orifice close to tip of penis. It is S-shaped in flaccid penis, while it is l-shaped in the erected penis.


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Male urethra can be divided into three parts

  1. Prostatic part of urethra (3cm long)
    It is crescentic on cross section with convexity. It passes through prostate at the junction of anterior 1I3rd and posterior 2/3rd of the gland. It is the widest and most dilatable part. It extends from neck of urinary bladder to prostatic utricle. It leaves the prostate through anterior surface close to apex.

Features in posterior wall:

  1. Urethral crest- median longitudinal mucus fold.
  2. Colliculus seminalis (verumonatanum): An elevation in the middle of urethral crest with the opening of prostatic utricle at its summit and ejaculatory duct on each side.
  3. Openings of ejaculatory ducts: These are present on each side of the orifice of utricle.
  4. Prostatic sinuses: These are vertical grooves present one on each side of urethral crest. They present with openings of prostatic glands.

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  1. Membranous part of urethra (15.2-2 cm long)
    It is stellate or irregular on cross-section. It is the shortest and least dilatable part of urethra. It runs from lower end of prostate through the deep perineal pouch and pierces the perineal membrane, 2.5 cms behind the lower border of public symphysis. It is the second narrowest part of urethra after external urethral orifice. It is surrounded by sphincter urethrae muscle. Bulbourethral gland is present on each side.
  2. Penile (spongy) part of urethra (15 cm long)
    It passes through bulb, body, and glans penis and terminates at the external urethral orifice close to the tip of the glans. It is longest part of urethra, on cross section; it is trapezoid at the bulb of penis transverse slit at the body and inverted T-shaped slit at the base of glans penis. It presents with two dilatations:
    1. Intrabulbar fossa, within the bulb and
    2. Navicular (terminal) fossa, within the glans penis.
      The ducts of bulbourethral glands open in the intra-bulbar fossa.
      There are urethral glands (Littre's gland) and urethral lacunae in spongy urethra.

The external urethral meatus is the narrowest part of urethra and is in the form of a sagittal slit about 4 mm long.


Lining epithelium

  1. Above the colliculus - Transitional epithelium.
  2. From the colliculus to commencement of terminal fossa - stratified columnar.
  3. Terminal fossa and external urethral orifice - non-keratinized stratified squamous.

Lymphatic drainage

  1. Prostatic and membranous parts drain into internal iliac nodes and spongy (penile) urethra drains into deep inguinal nodes.

Sphincters of urethra


Traditionally two sphincters are encountered:-

  1. Internal sphincter (sphincter vesicae):-It is involuntary and surrounds the internal urethral orifice.
  2. External sphincter (sphincter urethrae):- It is voluntary and surrounds membranous urethra.

Female Urethra

  1. Female urethra is shorter than male urethra, is 4 cm long and 6 mm in diameter. It begins at internal urethral orifice of bladder opposite to pubic symphysis and ends at external urethral orifice directly anterior to the opening of vagina and 2.5 cm behind glans clitoridis. On each side, near lower end of urethra, a number of mucous glands are grouped and open into paraurethral duct, on the lateral margins of external urethral orifice, Women do not possess internal urethral sphincter.
  2. Wall of urethra (both in males and females) has outer muscle coat and inner mucosa and is continuous with bladder.
  3. Most of the female urethra is lined by non-keratinized stratified squamous epithelium. However, close to internal urethral orifice, it is lined by transitional epithelium.
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Development of Urinary Bladder and Urethra

  1. The urinary bladder (except trigone) is derived from vesicourethral canal, cranial part of urogenital sinus (endodermal). Trigone is derived from absorbed part of Wolffian duct/mesonephric duct (mesodermal).
  2. Development of urethra is as follows :-
    1. Prostatic urethra and membranous urethra
      1. Anterior wall of prostatic urethra above the opening of prostatic utricle from vesicourethral canal (endoderm]
      2. Anterior wall of prostatic urethra below the opening of prostatic utricle and whole of the membranous urethra-s from definite urogenital sinus(endoderm)
      3. Posterior wall of prostatic urethra from mesonephric/Wolffian duct (mesodermal).
    2. Penile urethra
      1. Upto the glans → from phallic part of urogenital sinus (endoderm).
      2. In the glans → from ectodermal urethral groove (ectoderm).

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