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The urinary bladder is a musculomembranous sac that serves as a reservoir for urine, situated in the pelvic cavity, behind the pubic symphysis.
It is distensible, expanding into the abdominal cavity when filled.
Functionally, it acts as a temporary storage organ for urine and plays a role in micturition (urination).
Position:
In adults, when empty, it lies entirely in the pelvis.
When distended, it rises into the lower part of the abdomen.
In children, the bladder is more abdominal in position due to the shortness of the pelvis.
Capacity:
Average capacity: 150–500 mL (urge to void occurs around 300 mL).
Maximum distension: Up to 1 liter in pathological cases.
Shape:
Empty bladder: Tetrahedral.
Full bladder: Ovoid.
Parts:
Apex – directed upward and forward.
Base (fundus) – posterior surface.
Neck – lowest fixed part leading into the urethra.
Body – the main portion between apex and base.
The urinary bladder consists of a mucous membrane, submucosa, detrusor muscle layer, and an outer adventitia (or serosa).
The muscle coat, the detrusor muscle, is made of interlacing smooth muscle fibers arranged in three layers — outer longitudinal, middle circular, and inner longitudinal.
The bladder mucosa is lined by transitional epithelium (urothelium).
The internal surface is thrown into folds (rugae) when empty, except at the trigone, which remains smooth.
The trigone is a smooth triangular area on the internal surface of the bladder base between the two ureteric openings and the internal urethral orifice.
Functions:
Storage of urine under low pressure.
Contraction of detrusor and relaxation of sphincters during micturition expels urine.
When empty, the bladder appears four-sided (tetrahedral):
Apex
Points forward toward the upper border of the symphysis pubis.
Attached to the median umbilical ligament (remnant of urachus) extending up to the umbilicus.
Base (Fundus or Posterior Surface)
Triangular in shape and directed backward and downward.
In males: related to rectum and seminal vesicles.
In females: related to anterior wall of vagina and cervix of uterus.
Neck
Lowest and most fixed part of bladder, continuous with urethra.
Lies about 2.5 cm behind the lower border of the symphysis pubis.
Surrounded by the internal urethral sphincter (in males).
Anchored by puboprostatic (in males) or pubovesical (in females) ligaments.
Superior Surface
Triangular and covered by peritoneum.
In males: related to sigmoid colon and coils of ileum.
In females: related to uterus; the uterovesical pouch lies between them.
Inferolateral Surfaces
Two in number, rest on the levator ani, obturator internus, and pelvic fascia.
Meet anteriorly at the apex and posteriorly at the base.
In Males:
Superior surface: Covered by peritoneum; related to coils of ileum and sigmoid colon.
Base (posterior surface): Related to rectum, separated by rectovesical pouch, seminal vesicles, and vas deferens.
Inferolateral surfaces: Rest on levator ani, obturator internus, and fascia.
Neck: Lies above prostate gland; continuous with prostatic urethra.
In Females:
Superior surface: Related to body of uterus; separated by uterovesical pouch.
Base: Related to anterior vaginal wall and cervix.
Inferolateral surfaces: Rest on levator ani and obturator internus.
Neck: Lies against urogenital diaphragm; continuous with urethra.
Anterior Relation (in both sexes):
Separated from pubic symphysis by retropubic space (space of Retzius) containing fat and loose areolar tissue.
This space allows bladder expansion and surgical access (suprapubic cystostomy).
The bladder is held in position by true and false ligaments.
1. False Ligaments (peritoneal folds):
Median umbilical fold: Extends from apex of bladder to umbilicus; contains urachus.
Medial umbilical folds: Contain obliterated umbilical arteries.
Lateral false ligaments: Formed by peritoneal reflections on sides of bladder.
Rectovesical fold (in males) and uterovesical fold (in females): Peritoneal reflections connecting bladder to rectum or uterus.
2. True Ligaments (condensations of pelvic fascia):
Puboprostatic ligaments (in males) — connect neck of bladder and prostate to posterior surface of pubic bone.
Pubovesical ligaments (in females) — connect neck of bladder to pubic bone.
Lateral true ligaments — formed by thickening of fascia around the bladder neck and base, containing vesical veins.
Posterior ligament of bladder — condensation of fascia behind base of bladder containing vesical venous plexus.
Clinical importance:
These ligaments provide support and fixation to the bladder.
Weakness or disruption (e.g., after childbirth or surgery) can cause bladder descent or prolapse (cystocele).
The internal surface of the bladder is lined by transitional epithelium (urothelium).
When empty, the mucosa is thrown into folds (rugae) except in one region — the trigone — which is always smooth.
1. Trigone of the bladder:
A smooth triangular area on the posterior wall.
Its three angles correspond to:
Upper two angles: Openings of the right and left ureters.
Lower angle: Internal urethral orifice.
The interureteric ridge (bar of Mercier) joins the two ureteric orifices and forms the base of the trigone.
Beneath the trigone lies the uvula vesicae, a slight elevation caused by the median lobe of the prostate (in males).
2. Ureteric orifices:
Slit-like openings at the posterolateral angles of the trigone.
Function as valves preventing reflux of urine during bladder contraction.
3. Internal urethral orifice:
Lies at the neck of the bladder.
In males, surrounded by internal urethral sphincter (smooth muscle).
In females, no distinct internal sphincter is present.
Superior vesical arteries — branches of the umbilical artery (from internal iliac).
Inferior vesical artery (in males) — branch of internal iliac artery; supplies base, neck, prostate, and seminal vesicles.
Vaginal artery (in females) — replaces the inferior vesical branch.
Obturator and inferior gluteal arteries also give small branches to the bladder.
Clinical note:
During pelvic surgery, these small vessels must be carefully preserved to avoid bladder ischemia.
Veins form a rich vesical venous plexus around the base and neck of the bladder.
This plexus communicates with:
Prostatic venous plexus (in males).
Uterovaginal venous plexus (in females).
Internal iliac veins.
Clinical importance:
In males, infections or cancer of the prostate can spread to the bladder through the prostatic venous plexus.
Lymph from the bladder drains mainly into:
External iliac lymph nodes (superior part).
Internal iliac lymph nodes (inferior part).
Sacral lymph nodes (posterior part).
Clinical correlation:
Bladder carcinoma spreads first to external and internal iliac lymph nodes; this helps guide surgical lymph node dissection.
1. Sympathetic (T11–L2):
From hypogastric plexus.
Function: Relaxes detrusor muscle and contracts internal sphincter → promotes urine retention.
2. Parasympathetic (S2–S4):
From pelvic splanchnic nerves.
Function: Contracts detrusor and relaxes internal sphincter → promotes micturition.
3. Somatic (pudendal nerve, S2–S4):
Supplies external urethral sphincter (voluntary control).
Summary of control:
Filling phase: Sympathetic active → bladder relaxed, sphincters closed.
Voiding phase: Parasympathetic active → detrusor contracts, sphincters relax.
Reflex mechanism:
Micturition reflex arises when bladder stretch receptors activate parasympathetic outflow.
Under pontine and cortical control in adults; voluntary suppression possible.
Epithelium: Transitional epithelium (urothelium) that becomes thinner when distended.
Lamina propria: Loose connective tissue with elastic fibers and blood vessels.
Muscular coat (detrusor muscle):
Inner longitudinal, middle circular, and outer longitudinal smooth muscle layers.
Near the neck, middle circular fibers form internal urethral sphincter (in males).
Adventitia: Loose connective tissue with veins, lymphatics, and nerves.
Serosa (superior surface): Covered by peritoneum.
After reflecting the peritoneum from the anterior abdominal wall, the superior surface of the bladder can be exposed.
Identify median umbilical ligament (urachus remnant) extending from the apex to the umbilicus.
Trace ureters entering the posterior surface at the posterolateral angles of the trigone.
Open the bladder longitudinally to observe:
Trigone,
Interureteric ridge,
Ureteric and urethral orifices, and
Uvula vesicae (in males).
Note mucosal folds (rugae) except in the trigone region.
Cystitis: Inflammation of the bladder mucosa due to bacterial infection; more common in females because of short urethra.
Urinary retention: Failure of bladder emptying due to obstruction (prostatic enlargement, urethral stricture) or nerve injury.
Cystocele: Herniation of bladder wall into the vagina due to pelvic floor weakness.
Vesicoureteral reflux: Backflow of urine from bladder to ureters due to defective valve mechanism.
Bladder stones (vesical calculi): Form when urine stagnates; may cause hematuria or obstruction.
Exstrophy of bladder: Congenital anomaly where anterior bladder wall and lower abdominal wall fail to develop.
Neurogenic bladder: Results from spinal cord injury; causes loss of voluntary control of micturition.
Suprapubic cystostomy: Surgical drainage of urine through anterior bladder wall, accessed above pubic symphysis.
Bladder carcinoma: Commonly transitional cell carcinoma; spreads via lymphatics to iliac nodes.
Rupture of bladder: Can occur in pelvic fractures; urine may leak into peritoneal cavity (intraperitoneal rupture) or extraperitoneally (extraperitoneal rupture).
The urethra is a musculomembranous tube that conveys urine (and semen in males) to the exterior.
Lined by epithelium that varies along its course and surrounded by muscular coats.
Length:
Male urethra: ~18–20 cm.
Female urethra: ~4 cm.
Functions:
In males, it serves both urinary and reproductive functions.
In females, it serves only urinary function.
Extends from internal urethral orifice (at bladder neck) to external urethral orifice (at tip of glans penis).
Average length: 18–20 cm.
Divided into posterior and anterior parts.
Includes two segments:
Prostatic urethra (3 cm):
Lies within the prostate gland; widest and most dilatable portion.
Shape: Vertical slit on coronal section.
Features on posterior wall (urethral crest):
Verumontanum (seminal colliculus): Median elevation on posterior wall.
Prostatic utricle: Small blind pouch (vestige of Müllerian duct) opens in midline.
Openings of ejaculatory ducts: One on each side of utricle.
Prostatic sinuses: Grooves on either side of urethral crest; receive openings of prostatic ducts.
Relations:
Anterior: Symphysis pubis (separated by venous plexus).
Posterior: Rectal ampulla (separated by fascia).
Surrounding gland: Prostate.
Epithelium: Transitional epithelium continuous with bladder mucosa.
Membranous urethra (1–2 cm):
Narrowest and least dilatable part, except at external meatus.
Passes through the deep perineal pouch.
Surrounded by external urethral sphincter (voluntary muscle).
Pierces the perineal membrane and lies anterior to the bulbourethral glands (Cowper’s glands).
Epithelium: Pseudostratified columnar.
Clinical note:
This is the most easily injured part in pelvic fractures.
Bleeding at the external meatus and inability to pass urine indicate rupture here.
Includes two segments:
Bulbar urethra:
Begins at the base of the bulb of penis.
Slightly dilated (called ampulla of urethra).
Receives ducts of bulbourethral glands (Cowper’s glands).
Penile (spongy) urethra:
Runs through the corpus spongiosum up to the external urethral meatus.
Longest part of urethra (~15 cm).
Dilated at two points:
Bulbar fossa (posterior).
Navicular fossa (anterior) just within glans penis.
External urethral meatus: Narrowest part of entire urethra, with vertical slit-like opening at tip of glans.
Epithelium:
Proximal: Pseudostratified columnar.
Distal: Stratified squamous continuous with skin.
Mucous glands:
Numerous small urethral glands of Littre open into the lumen.
Urethral Stricture:
Fibrotic narrowing of urethra (usually after infection or trauma).
Common in bulbar urethra; causes poor urine stream and retention.
Rupture of Membranous Urethra:
Occurs in pelvic fractures; urine and blood collect in deep perineal pouch.
Patient unable to void; blood at external meatus.
Rupture of Spongy (Bulbar) Urethra:
Common in “straddle injury” (fall on crossbar of bicycle).
Urine extravasates into superficial perineal pouch, scrotum, penis, and lower abdominal wall, but not into thighs or anal triangle (limited by fascia).
Congenital Anomalies:
Hypospadias: External meatus opens on ventral surface of penis (failure of urethral folds to fuse).
Epispadias: External meatus opens on dorsal surface (usually associated with exstrophy of bladder).
Catheterization:
Urethra is curved in males; during catheterization, penis must be held upward to straighten the curve.
The narrowest and least dilatable point is the external urethral meatus.
Prostatic Enlargement:
Compresses prostatic urethra → difficulty in micturition and incomplete bladder emptying.
Urethral Calculus:
Small stones may lodge at constrictions:
Internal urethral orifice,
Membranous part,
External urethral meatus.
Cystoscopy and Urethroscopy:
Endoscopic procedures to visualize mucosa, identify obstructions or tumors.
The female urethra is a short, straight tube about 4 cm long and 6 mm wide, extending from the internal urethral orifice (at the bladder neck) to the external urethral orifice (in the vestibule of the vagina).
It serves only urinary function (unlike the male urethra).
Course:
Begins at the neck of the bladder, runs downward and forward, and opens in the vestibule, between the clitoris and vaginal orifice.
It is embedded in the anterior vaginal wall.
Relations:
Anteriorly: Pubic symphysis and retropubic venous plexus.
Posteriorly: Anterior vaginal wall.
Laterally: Pubourethral ligaments and paraurethral glands.
Openings:
External urethral orifice lies about 2.5 cm behind the clitoris and 2.5 cm in front of the vaginal opening.
Epithelium:
Proximal part: Transitional epithelium.
Middle part: Stratified columnar epithelium.
Distal part: Stratified squamous epithelium.
Special glands:
Paraurethral glands (Skene’s glands):
Homologous to male prostate.
Open near the external meatus on either side.
Secrete mucus for lubrication.
Sphincters:
Internal urethral sphincter (functional): Smooth muscle at bladder neck.
External urethral sphincter: Skeletal muscle fibers from sphincter urethrae and compressor urethrae in the deep perineal pouch; provides voluntary control of micturition.
The wall of the female urethra (and structurally similar layers in the male urethra) is composed of:
Mucous membrane:
Highly elastic; forms longitudinal folds.
Lined by transitional to stratified squamous epithelium.
Contains numerous urethral glands (glands of Littre).
Submucosa:
Rich in venous plexus, which contributes to urethral closure pressure.
Muscular coat:
Inner longitudinal and outer circular smooth muscle layers.
In the lower part, circular fibers are thickened to form a sphincter urethrae.
External voluntary muscle (striated) surrounds the lower half — supplied by the pudendal nerve (S2–S4).
Definition:
The process of emptying urine from the bladder through the urethra.
Phases:
Storage phase:
Controlled by sympathetic system (T11–L2).
Detrusor muscle relaxed; internal sphincter contracted.
External sphincter (voluntary control via pudendal nerve) remains contracted.
Voiding phase:
Controlled by parasympathetic system (S2–S4).
Detrusor contracts → increased bladder pressure.
Internal sphincter relaxes.
External sphincter voluntarily relaxed.
Micturition reflex:
Initiated when bladder fills (~300 mL); stretch receptors activate parasympathetic fibers.
Reflex centers located in sacral spinal cord (S2–S4).
Higher control:
Pontine micturition center (brainstem) coordinates reflex.
Cerebral cortex allows voluntary initiation or suppression.
In infants:
Reflex is automatic (spinal).
In adults:
Voluntary control developed through cortical regulation.
Urinary tract infection (UTI):
Common in females due to short urethra and proximity to vagina and anus.
Leads to dysuria (painful urination), frequency, urgency, and suprapubic pain.
Urethral stricture:
Narrowing of the urethra, rare in females; usually follows infection or trauma.
Stress urinary incontinence:
Leakage of urine during coughing or exertion.
Caused by weakness of pelvic floor or sphincter urethrae, commonly after childbirth or aging.
Urethral diverticulum:
Outpouching of urethral wall into the vaginal wall; may cause post-void dribbling and infection.
Cystocele:
Downward displacement of bladder and urethra into anterior vaginal wall due to levator ani weakness.
Neurogenic bladder:
Occurs in spinal cord injury or multiple sclerosis.
Loss of voluntary micturition; bladder may become spastic or flaccid.
Catheterization:
Easier in females because urethra is short, straight, and wide.
Care required to avoid infection or injury to mucosa.
Urethral caruncle:
Small, red, painful growth near external urethral meatus in postmenopausal women due to estrogen deficiency.
Urinary retention:
Inability to void urine; may result from urethral obstruction, prolapse, or nerve lesion.
Treated by catheterization or suprapubic cystostomy if prolonged.
The urinary bladder develops mainly from the vesicourethral part of the cloaca, which is derived from the endoderm of the urogenital sinus.
The cloaca, an endodermal cavity, is divided during development by the urorectal septum into:
Anterior part: Primitive urogenital sinus (gives rise to bladder and urethra).
Posterior part: Anorectal canal (forms rectum and anal canal).
Steps in Development:
Vesicourethral portion of urogenital sinus:
Forms the urinary bladder.
The upper part of the allantois becomes the urachus, which later obliterates to form the median umbilical ligament connecting bladder apex to the umbilicus.
Mesonephric ducts (Wolffian ducts):
Initially open into the posterior wall of the bladder.
Later, they are absorbed into the wall of the bladder to form part of the trigone region.
Their lower ends become the ejaculatory ducts in males.
Ureters:
Develop separately as outgrowths from the mesonephric ducts.
Their orifices are shifted cranially and laterally to open independently into the posterior wall of the bladder.
Lining epithelium:
Derived from endoderm (urogenital sinus).
The trigone, however, initially has mesodermal origin (from absorbed mesonephric ducts), but later becomes endodermal as the mucosa overgrows it.
1. In Males:
Develops from both endodermal urogenital sinus and ectodermal invagination.
Divided into three developmental regions:
a. Prostatic and membranous urethra:
- Develop from pelvic part of urogenital sinus (endodermal).
b. Spongy (penile) urethra:
- Develops from phallic part of urogenital sinus (endodermal).
- The distal part within the glans develops from an ectodermal invagination called the glandular plate, which later canalizes and joins the endodermal urethra.
c. Ejaculatory ducts:
- Formed from the lower parts of mesonephric ducts, which open into the prostatic urethra.
d. Prostatic utricle:
- Small midline pouch in the prostatic urethra, homologous to the uterus and vagina (from paramesonephric duct).
Epithelium:
Entirely endodermal, except the very terminal part (in glans), which is ectodermal.
2. In Females:
The female urethra develops entirely from the pelvic part of the urogenital sinus (endodermal).
The surrounding connective tissue and smooth muscle are derived from splanchnic mesoderm.
The paraurethral glands (Skene’s glands) develop as outgrowths from the urethral wall; they are homologous to the prostate gland in males.
Exstrophy of the bladder:
Due to failure of the anterior abdominal wall and anterior bladder wall to fuse.
Leads to exposure of the posterior bladder wall and ureteric orifices on the surface.
Patent urachus (Urachal fistula):
Failure of the urachus to close → urine discharges from the umbilicus.
Partial closure may result in a urachal sinus or urachal cyst.
Duplication of bladder:
Rare; occurs due to abnormal division of the cloaca or allantois.
Ectopic ureteric openings:
Ureter may open into vagina, vestibule, or urethra due to abnormal incorporation of the mesonephric ducts.
Hypospadias:
Failure of fusion of the urethral folds → external urethral meatus opens on ventral surface of penis.
Epispadias:
Urethral opening on dorsal surface of penis, often associated with exstrophy of bladder.
Congenital absence of urethra:
Extremely rare; results from complete failure of urogenital sinus development.
Urethral diverticulum:
Outpouching from urethral wall, may arise congenitally or secondarily from infection of paraurethral glands.
The urinary bladder is primarily endodermal in origin (urogenital sinus), with mesodermal contribution to its trigone.
The male urethra has dual origin — mostly endodermal, with distal ectodermal contribution.
The female urethra is wholly endodermal.
Developmental defects often reflect failure of midline fusion or malformation of cloacal derivatives, producing clinically significant anomalies such as exstrophy, urachal fistula, hypospadias, and epispadias.
The urinary bladder develops mainly from the vesicourethral part of the urogenital sinus, which is derived from endoderm.
The trigone of the bladder is initially formed from the mesoderm of the absorbed mesonephric ducts, but later becomes lined by endodermal epithelium.
The allantois becomes the urachus, which later fibroses to form the median umbilical ligament, connecting the bladder apex to the umbilicus.
The epithelium of the bladder is transitional (urothelium), allowing great distensibility.
The urinary bladder first lies in the abdomen in the fetus and gradually descends into the pelvis after birth.
The male urethra develops from both endodermal and ectodermal sources:
Prostatic and membranous parts → endoderm (pelvic part of urogenital sinus).
Spongy part → endoderm (phallic part of urogenital sinus).
Terminal part within glans → ectoderm (glandular plate).
The female urethra develops entirely from the endodermal pelvic part of the urogenital sinus.
The surrounding muscle and connective tissue of bladder and urethra are derived from splanchnic mesoderm.
The paraurethral glands (Skene’s glands) in females are homologous to the prostate gland in males.
The bulbourethral glands (Cowper’s glands) in males are homologous to the greater vestibular glands (Bartholin’s glands) in females.
The ureters arise as outgrowths of the mesonephric ducts, later attaining a separate opening in the bladder wall.
Exstrophy of the bladder results from failure of fusion of the anterior abdominal wall and anterior bladder wall.
Patent urachus leads to urine leakage from the umbilicus.
Hypospadias results from incomplete fusion of urethral folds, causing ventral urethral opening.
Epispadias results from abnormal positioning of the genital tubercle, leading to a dorsal urethral opening and association with bladder exstrophy.
The internal urethral sphincter (smooth muscle) is involuntary and present in males; the external sphincter (skeletal muscle) is voluntary and present in both sexes.
Micturition is a reflex act controlled by parasympathetic fibers (S2–S4) and regulated by pontine centers and the cerebral cortex.
Lymphatic drainage of the bladder is primarily to external and internal iliac nodes, while the urethra drains to inguinal nodes (distal part).
The urethral epithelium changes along its course — transitional → pseudostratified columnar → stratified squamous near the external orifice.
In both sexes, congenital or acquired abnormalities (strictures, diverticula, prolapse) are closely linked to developmental variations in these embryonic structures.
Case 1:
A newborn infant passes urine through the umbilicus instead of the urethral opening.
Question:
What is the developmental defect and its embryological basis?
Explanation:
The condition is due to a patent urachus — persistence of the allantoic canal, which normally obliterates to form the median umbilical ligament.
Urine escapes through the umbilicus because the channel between the bladder apex and umbilicus remains open.
Clinical management:
Surgical excision of the patent urachus and repair of the bladder wall are required to prevent infection and urine leakage.
Case 2:
A male infant presents with the urethral opening on the ventral surface of the penis.
Question:
What is the diagnosis, and what is its embryological cause?
Explanation:
Diagnosis: Hypospadias.
Caused by failure of fusion of the urethral folds during development of the penile urethra.
The external urethral meatus opens on the underside of the penis, scrotum, or perineum depending on the severity.
Clinical importance:
Hypospadias may cause abnormal urine stream and difficulty during sexual intercourse; corrected by surgical reconstruction (urethroplasty).
Case 3:
A child is born with the urethral opening on the dorsal surface of the penis, associated with exstrophy of the bladder.
Question:
Name the condition and explain its cause.
Explanation:
Condition: Epispadias, often occurring with bladder exstrophy.
Caused by abnormal positioning of the genital tubercle posterior to the urogenital membrane during development.
Leads to failure of midline fusion of the abdominal wall and exposure of the bladder mucosa.
Clinical insight:
Requires reconstructive surgery to restore urethral continuity and close the anterior bladder wall.
Case 4:
A 30-year-old woman complains of continuous urinary leakage despite normal urination. Examination reveals a small opening in the anterior vaginal wall.
Question:
What is the probable diagnosis, and how does it arise embryologically?
Explanation:
Diagnosis: Urethrovaginal fistula (or ectopic ureteric opening).
May result from abnormal incorporation of mesonephric duct into the bladder wall or defective partition of the cloaca.
The ureter opens ectopically into the vagina or urethra, leading to continuous dribbling of urine.
Treatment:
Surgical repositioning of the ureteric opening into the bladder.
Case 5:
A neonate shows a large defect in the lower abdominal wall with exposed, everted bladder mucosa.
Question:
What is the condition and embryological explanation?
Explanation:
Condition: Exstrophy of the urinary bladder.
Caused by failure of mesodermal migration between ectoderm and endoderm in the infraumbilical region, preventing formation of the anterior bladder wall and lower abdominal muscles.
The posterior bladder wall (mucosa) remains exposed through the abdominal wall defect.
Clinical importance:
Requires early surgical repair to cover the bladder and prevent infection or urinary leakage.
Case 6:
A young adult male presents with a midline suprapubic swelling that occasionally discharges clear fluid.
Question:
What is the possible diagnosis, and what structure is involved?
Explanation:
Diagnosis: Urachal cyst or sinus.
Caused by partial persistence of the urachus, where a cyst forms between the bladder and umbilicus.
May become infected or communicate intermittently with the bladder or umbilicus.
Treatment:
Complete surgical excision of the cyst and fibrous tract.
Case 7:
A male patient develops urinary retention following pelvic fracture. Imaging shows a tear in the membranous urethra.
Question:
Why is this site particularly vulnerable?
Explanation:
The membranous urethra passes through the urogenital diaphragm (deep perineal pouch) and is fixed at both ends — by the prostate above and bulb of penis below.
Sudden pelvic displacement causes rupture at this immobile segment.
Clinical consequence:
Urine and blood accumulate in the deep perineal pouch and pelvic region.
Immediate suprapubic cystostomy is required to drain urine and prevent extravasation.
Summary Insight:
Most developmental anomalies of the bladder and urethra result from:
Incomplete fusion of midline structures,
Abnormal descent or incorporation of ducts, or
Failure of canal closure (urachus or cloacal defects).
Understanding their embryological basis is vital for accurate diagnosis and surgical correction.
Q1. From which embryonic structure does the urinary bladder develop?
A. The bladder develops mainly from the vesicourethral part of the urogenital sinus, which is derived from endoderm.
Q2. What is the origin of the trigone of the bladder?
A. It is initially formed from mesoderm of the absorbed mesonephric ducts, but later becomes lined by endodermal epithelium.
Q3. What is the embryological origin of the urachus?
A. The urachus is a fibrous remnant of the allantois, which connects the apex of the bladder to the umbilicus and later becomes the median umbilical ligament.
Q4. How does the bladder position change after birth?
A. In the fetus and infant, the bladder lies abdominal, and as the pelvis develops, it gradually descends to become a pelvic organ in adults.
Q5. From what part of the urogenital sinus does the urethra develop?
A.
In males: From pelvic and phallic parts of the urogenital sinus (endoderm).
In females: Entirely from the pelvic part of the urogenital sinus.
Q6. What is the embryological origin of the male urethra?
A.
Prostatic and membranous urethra: Endodermal (pelvic part of urogenital sinus).
Spongy urethra: Endodermal (phallic part).
Terminal part within glans: Ectodermal (from glandular plate).
Q7. What is the origin of the female urethra?
A. Entirely from the pelvic part of the urogenital sinus (endoderm).
Q8. What is the origin of the connective tissue and smooth muscle of bladder and urethra?
A. They are derived from splanchnic mesoderm.
Q9. What are paraurethral (Skene’s) glands, and what is their male homolog?
A. The paraurethral glands in females are small mucus-secreting glands homologous to the prostate gland in males.
Q10. What are the bulbourethral (Cowper’s) glands, and what is their female homolog?
A. The bulbourethral glands in males correspond to the greater vestibular (Bartholin’s) glands in females.
Q11. How are ureters formed embryologically?
A. Each ureter develops as a bud from the mesonephric duct, which grows cranially and later opens independently into the posterior bladder wall.
Q12. What is exstrophy of the bladder?
A. A congenital defect where the anterior abdominal wall and anterior bladder wall fail to develop, leaving the posterior bladder wall exposed through a midline defect.
Q13. What is a patent urachus, and what are its effects?
A. A persistent urachus that remains open from the bladder to the umbilicus, causing urine to discharge from the umbilicus.
Q14. What are urachal anomalies other than patent urachus?
A.
Urachal cyst: Central part of urachus remains open.
Urachal sinus: Opens at the umbilical end only.
Urachal fistula: Entire canal remains open to both bladder and umbilicus.
Q15. What is hypospadias?
A. A condition where the external urethral opening appears on the ventral (underside) surface of the penis due to failure of fusion of urethral folds.
Q16. What is epispadias?
A. A defect where the urethral opening is on the dorsal surface of the penis, usually associated with bladder exstrophy and abnormal development of the genital tubercle.
Q17. What is the difference between hypospadias and epispadias?
A.
Hypospadias: Ventral opening, failure of urethral fold fusion.
Epispadias: Dorsal opening, due to misplaced genital tubercle.
Q18. What is a urachal cyst, and where is it located?
A. A fluid-filled cystic swelling in the midline between the bladder and umbilicus, caused by partial persistence of urachus.
Q19. What is the embryological origin of the prostatic utricle?
A. Derived from the Müllerian (paramesonephric) ducts, homologous to the uterus and vagina in females.
Q20. What causes duplication of the bladder?
A. Abnormal division of the cloaca or allantois during early embryonic development.
Q21. What are the possible sites of ectopic ureteric openings?
A. In males — prostatic urethra, seminal vesicle, or vas deferens;
In females — vagina, vestibule, or urethra.
Q22. What is the significance of trigone formation in the bladder?
A. The trigone marks the site of incorporation of mesonephric ducts and ureteric buds, forming a smooth area important for the orientation of ureteric orifices and prevention of reflux.
Q23. What is the embryological explanation for a urachal sinus opening at the umbilicus?
A. Failure of the upper part of the urachus to close, leaving a blind-ending tract open at the umbilicus.
Q24. Why are urinary anomalies often midline defects?
A. Because the urinary system develops from midline endodermal structures (cloaca, urogenital sinus, allantois), and failure of fusion or closure along the midline leads to such anomalies.
Q25. What is the clinical importance of knowing bladder and urethral development?
A. It helps in diagnosing and surgically managing congenital anomalies like exstrophy, hypospadias, patent urachus, and ectopic ureters accurately.
Summary Insight:
Understanding the developmental anatomy of the bladder and urethra explains many congenital disorders. Most anomalies result from persistence of embryonic channels, faulty fusion of midline folds, or misplacement of duct openings, all of which are correctable with precise surgical intervention.
1. The urinary bladder develops from which embryonic structure?
A. Mesonephric duct
B. Metanephric blastema
C. Vesicourethral part of the urogenital sinus
D. Allantois
→ Answer: C. Vesicourethral part of the urogenital sinus
2. The epithelium of the urinary bladder is derived from:
A. Mesoderm
B. Endoderm
C. Ectoderm
D. Neural crest
→ Answer: B. Endoderm
3. The trigone of the bladder is formed from:
A. Cloaca
B. Allantois
C. Absorbed mesonephric ducts
D. Metanephric blastema
→ Answer: C. Absorbed mesonephric ducts
4. What is the adult derivative of the allantois?
A. Median umbilical ligament
B. Medial umbilical ligament
C. Lateral umbilical ligament
D. Round ligament of liver
→ Answer: A. Median umbilical ligament
5. The urachus connects which two structures during development?
A. Umbilicus and rectum
B. Bladder and umbilicus
C. Cloaca and urethra
D. Ureter and kidney
→ Answer: B. Bladder and umbilicus
6. The prostatic and membranous parts of the male urethra develop from:
A. Pelvic part of urogenital sinus
B. Phallic part of urogenital sinus
C. Ectodermal invagination
D. Mesonephric duct
→ Answer: A. Pelvic part of urogenital sinus
7. The spongy part of the male urethra develops from:
A. Mesonephric duct
B. Pelvic part of urogenital sinus
C. Phallic part of urogenital sinus
D. Glandular plate (ectodermal)
→ Answer: C. Phallic part of urogenital sinus
8. The terminal part of the male urethra in the glans penis develops from:
A. Endoderm
B. Mesoderm
C. Ectoderm
D. Neural crest
→ Answer: C. Ectoderm
9. The female urethra develops from which embryonic structure?
A. Pelvic part of the urogenital sinus
B. Phallic part of the urogenital sinus
C. Mesonephric duct
D. Paramesonephric duct
→ Answer: A. Pelvic part of the urogenital sinus
10. The connective tissue and smooth muscle of the bladder are derived from:
A. Endoderm
B. Ectoderm
C. Splanchnic mesoderm
D. Somatic mesoderm
→ Answer: C. Splanchnic mesoderm
11. Which of the following glands in females is homologous to the prostate gland in males?
A. Bartholin’s gland
B. Skene’s gland (paraurethral gland)
C. Vestibular gland
D. Cowper’s gland
→ Answer: B. Skene’s gland (paraurethral gland)
12. Which of the following glands in females corresponds to the bulbourethral (Cowper’s) glands of males?
A. Skene’s glands
B. Bartholin’s glands
C. Vestibular glands
D. Urethral glands
→ Answer: B. Bartholin’s glands
13. The ureters develop as outgrowths from:
A. Urogenital sinus
B. Mesonephric ducts
C. Metanephric blastema
D. Cloaca
→ Answer: B. Mesonephric ducts
14. Failure of the anterior abdominal wall and bladder wall to develop results in:
A. Epispadias
B. Hypospadias
C. Exstrophy of bladder
D. Patent urachus
→ Answer: C. Exstrophy of bladder
15. Urine leakage from the umbilicus in a newborn is due to:
A. Patent urachus
B. Hypospadias
C. Epispadias
D. Bladder exstrophy
→ Answer: A. Patent urachus
16. Hypospadias occurs due to:
A. Failure of fusion of urethral folds
B. Failure of descent of testes
C. Abnormal position of genital tubercle
D. Persistence of urachus
→ Answer: A. Failure of fusion of urethral folds
17. Epispadias is associated with:
A. Failure of urethral fold fusion
B. Abnormal position of genital tubercle
C. Incomplete cloacal division
D. Failure of mesonephric duct absorption
→ Answer: B. Abnormal position of genital tubercle
18. The prostatic utricle in males is homologous to which female structure?
A. Vagina
B. Uterus and vagina
C. Uterine tube
D. Ovary
→ Answer: B. Uterus and vagina
19. Which of the following is a remnant of the mesonephric duct in males?
A. Ureter
B. Ejaculatory duct
C. Urachus
D. Seminal vesicle
→ Answer: B. Ejaculatory duct
20. The most common site for ectopic ureteric opening in females is:
A. Urethra
B. Vestibule
C. Vagina
D. Uterus
→ Answer: C. Vagina
21. Duplication of the bladder results from:
A. Abnormal division of the cloaca
B. Incomplete descent of ureter
C. Failure of urachus closure
D. Fusion of mesonephric ducts
→ Answer: A. Abnormal division of the cloaca
22. The lumen of the urachus normally disappears during:
A. 2nd month of intrauterine life
B. 4th month of intrauterine life
C. 6th month of intrauterine life
D. At birth
→ Answer: B. 4th month of intrauterine life
23. Which of the following anomalies is due to partial persistence of the urachus?
A. Urachal fistula
B. Urachal sinus or cyst
C. Patent urachus
D. Exstrophy of bladder
→ Answer: B. Urachal sinus or cyst
24. Which congenital anomaly causes a dorsal urethral opening?
A. Epispadias
B. Hypospadias
C. Urachal fistula
D. Cloacal malformation
→ Answer: A. Epispadias
25. Which congenital anomaly causes a ventral urethral opening?
A. Hypospadias
B. Epispadias
C. Patent urachus
D. Urethral diverticulum
→ Answer: A. Hypospadias
26. The epithelial lining of the urinary bladder is:
A. Stratified squamous
B. Transitional epithelium
C. Cuboidal epithelium
D. Columnar epithelium
→ Answer: B. Transitional epithelium
27. Micturition reflex is mediated mainly by:
A. Sympathetic fibers (T11–L2)
B. Parasympathetic fibers (S2–S4)
C. Somatic fibers (L4–S1)
D. Hypogastric plexus alone
→ Answer: B. Parasympathetic fibers (S2–S4)
28. The muscle responsible for bladder contraction during urination is:
A. Levator ani
B. Detrusor muscle
C. Sphincter urethrae
D. Obturator internus
→ Answer: B. Detrusor muscle
29. The external urethral sphincter is supplied by:
A. Sympathetic nerves
B. Pelvic splanchnic nerves
C. Pudendal nerve
D. Hypogastric plexus
→ Answer: C. Pudendal nerve
30. The lymphatic drainage of the bladder primarily reaches:
A. Inguinal nodes
B. Internal and external iliac nodes
C. Para-aortic nodes
D. Sacral nodes only
→ Answer: B. Internal and external iliac nodes
Q1. What is the embryological origin of the urinary bladder?
A. It develops from the vesicourethral part of the urogenital sinus, which is endodermal in origin.
Q2. What forms the trigone of the bladder?
A. The trigone is formed by the absorption of the mesonephric ducts into the posterior wall of the bladder.
It is initially mesodermal but later lined by endodermal epithelium.
Q3. What is the fate of the allantois?
A. The allantois becomes the urachus, which later fibroses to form the median umbilical ligament connecting the bladder apex to the umbilicus.
Q4. What is the epithelial lining of the urinary bladder?
A. The bladder is lined by transitional epithelium (urothelium) that allows stretching during filling.
Q5. What is the position of the bladder in infants and adults?
A.
In infants, the bladder is abdominal in position.
In adults, it becomes a pelvic organ as the pelvis enlarges.
Q6. From which structure does the male urethra develop?
A. The male urethra develops from both endodermal urogenital sinus and ectodermal invagination at the glans penis.
Q7. From which structure does the female urethra develop?
A. The female urethra develops entirely from the pelvic part of the urogenital sinus (endodermal).
Q8. What is the embryological origin of the ureters?
A. The ureters develop as outgrowths from the mesonephric ducts, which later open separately into the bladder wall.
Q9. What is the function of the detrusor muscle?
A. The detrusor muscle contracts during micturition to expel urine from the bladder.
Q10. What is the nerve supply of the urinary bladder?
A.
Parasympathetic (S2–S4): Motor to detrusor, inhibitory to sphincter.
Sympathetic (T11–L2): Inhibitory to detrusor, motor to internal sphincter.
Somatic (pudendal nerve): Voluntary control of external sphincter.
Q11. What initiates the micturition reflex?
A. Stretch receptors in the bladder wall stimulate parasympathetic centers (S2–S4) when the bladder fills (~300 mL).
Q12. What is the difference between the internal and external urethral sphincters?
A.
Internal sphincter: Smooth muscle, involuntary, located at bladder neck.
External sphincter: Skeletal muscle, voluntary, located in deep perineal pouch.
Q13. What are the homologous structures of the prostate and paraurethral glands?
A. The paraurethral (Skene’s) glands in females are homologous to the prostate gland in males.
Q14. What are the homologous structures of Cowper’s and Bartholin’s glands?
A. The Cowper’s glands (bulbourethral glands) in males correspond to the Bartholin’s glands (greater vestibular glands) in females.
Q15. What are the common congenital anomalies of the urinary bladder?
A.
Exstrophy of bladder
Patent urachus
Urachal cyst or sinus
Duplication of bladder
Q16. What causes urine leakage from the umbilicus in a newborn?
A. It is due to a patent urachus, where the connection between the bladder and umbilicus fails to close.
Q17. What is exstrophy of the bladder?
A. A condition in which the anterior bladder wall and anterior abdominal wall fail to fuse, exposing the bladder mucosa.
Q18. What is hypospadias?
A. An abnormality where the urethral opening is on the ventral surface of the penis, due to failure of fusion of urethral folds.
Q19. What is epispadias?
A. An abnormality where the urethral opening is on the dorsal surface of the penis, usually associated with bladder exstrophy.
Q20. What is the difference between hypospadias and epispadias?
A.
Hypospadias: Ventral opening; due to failed fusion of urethral folds.
Epispadias: Dorsal opening; due to misplacement of the genital tubercle.
Q21. What is a urachal cyst?
A. A fluid-filled midline swelling between the bladder and umbilicus due to partial persistence of urachus.
Q22. What is the prostatic utricle, and what is its significance?
A. The prostatic utricle is a small midline pouch in the prostatic urethra, homologous to the uterus and vagina in females.
Q23. What are the common sites of ectopic ureteric openings?
A.
Males: Prostatic urethra, seminal vesicle, or vas deferens.
Females: Vagina, vestibule, or urethra.
Q24. What is the most dilatable part of the male urethra?
A. The prostatic urethra.
Q25. What is the narrowest part of the male urethra?
A. The external urethral meatus.
Q26. Which part of the male urethra is most prone to injury in pelvic fractures?
A. The membranous urethra.
Q27. Which part of the male urethra is most commonly affected in stricture formation?
A. The bulbar urethra.
Q28. What is the function of the urethral glands (glands of Littre)?
A. They secrete mucus to lubricate the urethra and facilitate passage of urine or semen.
Q29. Which nerve provides voluntary control of micturition?
A. The pudendal nerve (S2–S4) controlling the external urethral sphincter.
Q30. What is the lymphatic drainage of the bladder?
A. Mainly to internal and external iliac lymph nodes; the trigone may also drain to sacral nodes.
Q31. What is the lymphatic drainage of the distal urethra?
A. To the superficial inguinal lymph nodes.
Q32. What are the main differences between male and female urethra?
A.
Length: Male 18–20 cm; Female 4 cm.
Function: Male – urinary and reproductive; Female – urinary only.
Course: Male – curved; Female – straight.
Sphincter: Both have external sphincter; internal sphincter present only in males.
Q33. What is the clinical significance of knowing urethral curvatures in males?
A. During catheterization, the penis must be lifted to straighten the urethral curve and prevent injury or false passage.
Q34. What is the nerve root value of the micturition reflex?
A. S2, S3, and S4 spinal segments.
Q35. Why is urinary infection more common in females?
A. Because the urethra is short, straight, and close to the vagina and anus, facilitating ascending infection.
Q36. What is stress urinary incontinence?
A. Involuntary leakage of urine during coughing or exertion due to weakness of pelvic floor or sphincter urethrae, commonly after childbirth.
Q37. What is cystocele?
A. Downward protrusion of the urinary bladder into the anterior vaginal wall due to weakness of levator ani and pelvic fascia.
Q38. What is the developmental cause of exstrophy–epispadias complex?
A. Failure of mesodermal migration between ectoderm and endoderm in the infraumbilical region, resulting in absence of the anterior bladder wall and pubic separation.
Q39. What is the importance of trigone smoothness in cystoscopy?
A. A smooth trigone indicates normal development; irregularity or elevation may suggest pathology such as inflammation or tumor.
Q40. What is the homology of male and female urethra?
A. Both are derived from the urogenital sinus, though the male urethra extends further due to the development of external genitalia.
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