Urology

Chapter: Urinary System; Topic: Ureter Anatomy; Subtopic: Anatomical Constrictions of the Ureter

Keyword Definitions:

• Ureter: Muscular tube carrying urine from kidney to bladder.

• Ureteric Constrictions: Narrow points where obstruction (stones) commonly occurs.

• Pelviureteric Junction (PUJ): Junction of renal pelvis and ureter; one of the narrowest points.

• Pelvic Brim: Area where ureter crosses external iliac vessels.

• Vesicoureteric Junction (VUJ): Entry of ureter into bladder; the narrowest ureteric site.

1) Lead Question – 2016
Narrowest part of ureter is ?
a) Brim of the pelvis
b) Crossing by gonadal vessels
c) Vesicouretric junction
d) Crossing by ductus deferens

Answer: c) Vesicoureteric junction

Explanation: The ureter has three classical narrowings: the pelviureteric junction (PUJ), the crossing of the iliac vessels at the pelvic brim, and the vesicoureteric junction (VUJ). Among these, the VUJ is the *narrowest* physiologic point and is the most common site for ureteric stone impaction. At this junction, the ureter enters the bladder in an oblique intramural course offering high resistance. Other options represent relative constrictions, but none is as narrow as the VUJ.

2) Most common site of ureteric stone impaction?
a) PUJ
b) Pelvic brim
c) VUJ
d) Mid ureter

Answer: c) VUJ

Explanation: The VUJ has the smallest lumen.

3) Ureter is lined by?
a) Stratified squamous
b) Transitional epithelium
c) Cuboidal
d) Pseudostratified

Answer: b) Transitional epithelium

Explanation: Urothelium allows stretch.

4) Ureter crosses which vessel at pelvic brim?
a) Internal iliac artery
b) External iliac artery
c) Inferior epigastric artery
d) Obturator artery

Answer: b) External iliac artery

Explanation: Classical pelvic landmark.

5) Blood supply to upper ureter from?
a) Renal artery
b) Superior rectal artery
c) Gonadal artery
d) Obturator artery

Answer: a) Renal artery

Explanation: Segmental branches supply the upper third.

6) Ureter crosses ductus deferens in?
a) Abdomen
b) Pelvis
c) Perineum
d) Inguinal canal

Answer: b) Pelvis

Explanation: Near the bladder base.

7) Normal length of adult ureter?
a) 10 cm
b) 15 cm
c) 25–30 cm
d) 40 cm

Answer: c) 25–30 cm

Explanation: Extends from renal pelvis to urinary bladder.

8) Pain from upper ureter radiates to?
a) Perineum
b) Flank
c) Testis/labia
d) Suprapubic area

Answer: b) Flank

Explanation: T10–T12 dermatomal referral.

9) Ureteric peristalsis is chiefly regulated by?
a) Sympathetic nerves
b) Parasympathetic nerves
c) Intrinsic pacemaker cells
d) Voluntary control

Answer: c) Intrinsic pacemaker cells

Explanation: Ureter contracts independently of autonomic control.

10) Ureter is retroperitoneal?
a) Yes
b) No
c) Intraperitoneal
d) Subperitoneal

Answer: a) Yes

Explanation: Entire ureter lies within retroperitoneum.

11) Ureter enters bladder wall at what angle?
a) Vertical
b) Horizontal
c) Oblique
d) Curved

Answer: c) Oblique

Explanation: Oblique entry prevents vesicoureteral reflux.

Chapter: Retroperitoneum; Topic: Kidney Coverings; Subtopic: Renal Fascia (Gerota’s Fascia)

Keyword Definitions:

• Gerota’s Fascia: Fibrous renal fascia enclosing kidney and adrenal gland.

• Perirenal Fat: Fat layer immediately surrounding the kidney within Gerota’s fascia.

• Pararenal Fat: Fat outside renal fascia providing extra cushioning.

• Renal Capsule: Dense fibrous layer directly covering kidney surface.

• Retroperitoneum: Space behind peritoneum containing kidneys, ureters, adrenals.

1) Lead Question – 2016
Kidney is covered by what fascia?
a) Sibson's fascia
b) Buck's fascia
c) Gerota's fascia
d) None

Answer: c) Gerota's fascia

Explanation: The kidney is enclosed by three major coverings: the renal capsule, perirenal fat, and Gerota’s fascia, also called the renal fascia. Gerota’s fascia forms a tough connective-tissue sheath around the kidney and adrenal gland, anchoring them to posterior abdominal structures. Sibson’s fascia is cervical, and Buck’s fascia belongs to the penis; hence, neither covers the kidney. The fascia is crucial for limiting the spread of perinephric infections and maintaining renal position within the retroperitoneum.

2) Perirenal fat is located?
a) Inside renal capsule
b) Between capsule and renal fascia
c) Outside Gerota’s fascia
d) Only at upper pole

Answer: b) Between capsule and renal fascia

Explanation: Perirenal fat forms a major protective cushion around each kidney.

3) Pararenal fat lies?
a) Deep to renal capsule
b) Deep to Gerota’s fascia
c) Superficial to Gerota’s fascia
d) Between cortex and medulla

Answer: c) Superficial to Gerota’s fascia

Explanation: Pararenal fat occupies the outermost layer, supporting the kidneys.

4) Renal capsule is?
a) Peritoneal lining
b) Tough fibrous coat of kidney
c) Layer of fascia surrounding adrenal only
d) Loose areolar tissue

Answer: b) Tough fibrous coat of kidney

Explanation: It adheres closely to renal parenchyma and protects from infection.

5) Which structure shares Gerota’s fascia with kidney?
a) Pancreas
b) Adrenal gland
c) Gall bladder
d) Duodenum

Answer: b) Adrenal gland

Explanation: Kidney and ipsilateral adrenal lie together within same fascial compartment.

6) Perinephric abscess is limited by?
a) Parietal peritoneum
b) Renal capsule
c) Gerota’s fascia
d) Iliac fascia

Answer: c) Gerota’s fascia

Explanation: Gerota’s fascia restricts spread superiorly and inferiorly, localizing abscesses.

7) Which muscle lies posterior to kidney?
a) Psoas major
b) Rectus abdominis
c) Iliacus
d) Internal oblique

Answer: a) Psoas major

Explanation: Posterior relations include psoas major, quadratus lumborum, and diaphragm.

8) Kidney is located at which vertebral level?
a) T8–T10
b) T12–L3
c) L3–L5
d) T6–T8

Answer: b) T12–L3

Explanation: Right kidney lies slightly lower due to liver size above it.

9) Which structure lies anterior to right kidney?
a) Stomach
b) Spleen
c) Liver
d) Tail of pancreas

Answer: c) Liver

Explanation: Right kidney contacts liver, duodenum, right colic flexure.

10) Which structure lies anterior to left kidney?
a) Duodenum
b) Liver
c) Jejunum
d) Ascending colon

Answer: c) Jejunum

Explanation: Left kidney relations include stomach, spleen, pancreas, jejunum.

11) Renal fascia blends inferiorly with?
a) Pelvic diaphragm
b) Iliac fascia
c) Transversalis fascia
d) Pouch of Douglas

Answer: b) Iliac fascia

Explanation: Inferior continuation helps anchor kidney within retroperitoneum.

Chapter: Histology; Topic: Renal Tubule System; Subtopic: Loop of Henle (Ansa Nephroni)

Keyword Definitions:

• Ansa Nephroni (Loop of Henle): U-shaped part of nephron consisting of descending limb, thin limb, and thick ascending limb.

• Thin Limb Epithelium: Simple squamous epithelium allowing passive water movement.

• Thick Ascending Limb: Cuboidal to low columnar epithelium performing active ion transport.

• Juxtamedullary Nephron: Nephrons with long loops of Henle contributing to urine concentration.

• Countercurrent Mechanism: Passive and active transport system enhancing medullary osmotic gradient.

1) Lead Question – 2016
Ansa nephroni is lined by?
A) Columnar
B) Squamous epithelium
C) Cuboidal and columnar epithelium
D) Stratified squamous epithelium

Answer: C) Cuboidal and columnar epithelium

Explanation: The Loop of Henle (Ansa nephroni) has different epithelial linings depending on the segment. The thin descending and thin ascending limbs are lined by simple squamous epithelium, facilitating passive movement of water and solutes. However, the thick ascending limb—an essential component of Ansa nephroni—is lined by simple cuboidal to low columnar epithelium responsible for active Na⁺/K⁺/Cl⁻ transport. Because the thick segment is the functional component emphasized in exam questions, the best answer is option C, representing the cuboidal/columnar lining of the thick limb.

2) The thin descending limb of Loop of Henle is highly permeable to–
A) Sodium
B) Water
C) Urea
D) Glucose

Answer: B) Water

Explanation: Simple squamous epithelium of thin descending limb allows passive water movement, concentrating tubular fluid. Thus, B is correct.

3) The thick ascending limb is impermeable to–
A) Sodium
B) Potassium
C) Water
D) Chloride

Answer: C) Water

Explanation: The thick ascending limb actively reabsorbs ions but is water-impermeable, crucial for countercurrent multiplication. Thus, C is correct.

4) Which transporter is characteristic of thick ascending limb?
A) Na⁺/Cl⁻ cotransporter
B) NKCC2 transporter
C) Aquaporin-2
D) ENaC channels

Answer: B) NKCC2 transporter

Explanation: NKCC2 is responsible for Na⁺/K⁺/2Cl⁻ reabsorption in thick ascending limb. Thus, B is correct.

5) A patient taking loop diuretics has blockade of which nephron segment?
A) Proximal tubule
B) Thin descending limb
C) Thick ascending limb
D) Collecting duct

Answer: C) Thick ascending limb

Explanation: Loop diuretics inhibit NKCC2 transporter in thick ascending limb. Thus, C is correct.

6) Which epithelium lines the proximal convoluted tubule?
A) Simple squamous
B) Simple cuboidal with brush border
C) Stratified columnar
D) Transitional epithelium

Answer: B) Simple cuboidal with brush border

Explanation: PCT has dense microvilli for reabsorption. Thus, B is correct.

7) Medullary osmotic gradient is primarily generated by–
A) PCT
B) Loop of Henle
C) Collecting duct
D) Renal corpuscle

Answer: B) Loop of Henle

Explanation: Countercurrent multiplier in Loop of Henle generates gradient. Thus, B is correct.

8) Vasa recta capillaries run parallel to–
A) PCT
B) DCT
C) Loop of Henle
D) Collecting duct

Answer: C) Loop of Henle

Explanation: Vasa recta maintain medullary osmotic gradient by countercurrent exchange. Thus, C is correct.

9) The longest loop of Henle is found in–
A) Cortical nephrons
B) Juxtamedullary nephrons
C) Medullary rays
D) Renal sinus

Answer: B) Juxtamedullary nephrons

Explanation: These nephrons create concentrated urine. Thus, B is correct.

10) Which part of nephron has macula densa?
A) PCT
B) Thick ascending limb
C) Thin descending limb
D) Bowman’s capsule

Answer: B) Thick ascending limb

Explanation: Macula densa detects NaCl concentration and regulates GFR. Thus, B is correct.

11) A biopsy shows simple squamous epithelium in nephron. This is most likely–
A) PCT
B) Thick ascending limb
C) Thin limb of Loop of Henle
D) Collecting duct

Answer: C) Thin limb of Loop of Henle

Explanation: Thin limbs are lined by simple squamous cells for passive exchange. Thus, C is correct.

Chapter: Histology; Topic: Urinary System; Subtopic: Epithelial Lining of Urinary Tract

Keyword Definitions:

• Transitional Epithelium (Urothelium): Stratified epithelium specialized for stretch, lines renal pelvis to proximal urethra.

• Dome Cells: Superficial umbrella cells characteristic of bladder epithelium.

• Stratified Squamous Epithelium: Protective epithelium seen in distal urethra.

• Cuboidal Epithelium: Single-layered epithelium seen in ducts and tubules, not bladder.

• Columnar Epithelium: Tall cells lining absorptive or secretory surfaces, not bladder.

1) Lead Question – 2016
Epithelial lining of urinary bladder?
A) Squamous
B) Transitional
C) Cuboidal
D) Columnar

Answer: B) Transitional

Explanation: The urinary bladder is lined by transitional epithelium, also known as urothelium. This specialized epithelium can stretch considerably, allowing the bladder to accommodate changes in volume. Superficial umbrella cells help maintain a barrier against urine’s toxic solutes. Squamous epithelium is found in the distal urethra, cuboidal epithelium in kidney tubules, and columnar epithelium in glandular organs. Thus, the correct answer is B. The unique structure of transitional epithelium provides both distensibility and protection, which are essential for bladder function and urinary tract integrity.

2) Transitional epithelium is found in all of the following except–
A) Renal pelvis
B) Ureter
C) Bladder
D) Collecting ducts

Answer: D) Collecting ducts

Explanation: Transitional epithelium lines the renal pelvis, ureters, and urinary bladder. Collecting ducts, however, are lined by simple cuboidal to columnar epithelium, not urothelium. This distinction is important because transitional epithelium must stretch in response to urine storage and transport, a feature unnecessary in collecting ducts. Therefore, D is the correct answer. Recognizing these epithelial differences helps in diagnosing urinary tract disorders and interpreting histopathological slides accurately.

3) A biopsy from a patient with chronic cystitis shows umbrella cells. These cells indicate–
A) Metaplasia
B) Transitional epithelium
C) Keratinizing squamous epithelium
D) Cuboidal epithelium

Answer: B) Transitional epithelium

Explanation: Umbrella cells are the superficial layer of transitional epithelium, characteristic of the bladder. Their presence indicates an intact urothelial lining. Metaplasia would show squamous or glandular changes instead. Keratinizing epithelium is found in skin, not bladder. Cuboidal epithelium lines renal tubules. Thus, B is correct. These dome-shaped cells maintain a barrier and contribute to bladder function, especially during distension.

4) The epithelium most resistant to stretching is–
A) Simple squamous
B) Transitional
C) Simple cuboidal
D) Stratified columnar

Answer: B) Transitional

Explanation: Transitional epithelium is uniquely adapted to withstand distension without losing integrity. Simple squamous and cuboidal epithelia cannot stretch significantly. Stratified columnar epithelium is rare and not adapted for stretch. Therefore, B is correct. The urothelium’s structural specialization helps prevent damage from repeated filling and emptying cycles in the urinary bladder and ureters.

5) A man with long-standing bladder outlet obstruction shows thickened bladder wall. Which epithelial change is most likely?
A) Transitional epithelium hypertrophy
B) Squamous metaplasia
C) Cuboidal proliferation
D) Columnar transformation

Answer: A) Transitional epithelium hypertrophy

Explanation: Chronic bladder outlet obstruction increases intravesical pressure, causing thickening of the bladder wall. The transitional epithelium may undergo hypertrophy but generally remains urothelial. Squamous metaplasia occurs with chronic irritation but is less typical. Cuboidal or columnar changes do not occur in bladder lining. Thus, A is correct, reflecting compensatory epithelial and muscular responses to obstruction.

6) The proximal urethra in males is lined by which epithelium?
A) Transitional
B) Stratified squamous keratinized
C) Simple columnar
D) Cuboidal

Answer: A) Transitional

Explanation: The male proximal urethra is lined by transitional epithelium continuous with the bladder. Stratified squamous appears in the distal urethra, columnar epithelium in parts of the prostatic urethra, and cuboidal in ducts and tubules. Thus, A is correct. This continuity helps maintain a flexible, protective mucosal lining accommodating urine flow and mechanical stress.

7) A child with vesicoureteral reflux may have weakening of which epithelial layer?
A) Columnar
B) Cuboidal
C) Transitional
D) Stratified squamous

Answer: C) Transitional

Explanation: Vesicoureteral reflux involves dysfunction in the ureterovesical junction, lined by transitional epithelium. Weakness in this epithelium or underlying structures predisposes to urine reflux and infections. Squamous, cuboidal, and columnar epithelia are not part of this region. Thus, C is correct. Proper function of urothelium is essential to prevent ascending infections and protect upper urinary tract structures.

8) Urothelial carcinoma arises from which epithelium?
A) Transitional
B) Squamous
C) Columnar
D) Cuboidal

Answer: A) Transitional

Explanation: Urothelial carcinoma, the most common bladder cancer, originates from transitional epithelium. Squamous tumors arise from squamous metaplasia, columnar tumors from glandular metaplasia, and cuboidal epithelium does not give rise to bladder carcinoma. Thus, A is correct. Risk factors include smoking, occupational exposures, and chronic irritation, all affecting the urothelium.

9) In hydronephrosis, the renal pelvis shows dilatation of epithelium normally lined by–
A) Transitional epithelium
B) Simple squamous epithelium
C) Columnar epithelium
D) Pseudostratified epithelium

Answer: A) Transitional epithelium

Explanation: The renal pelvis is lined by transitional epithelium, enabling distensibility. Hydronephrosis causes dilation but the epithelial type remains transitional. Simple squamous lines Bowman’s capsule, columnar lines GI tract, and pseudostratified lines respiratory tract. Thus, A is correct. The urothelium’s stretchability helps accommodate increased pressure but prolonged obstruction leads to damage.

10) Terminal male urethra is lined by–
A) Stratified squamous non-keratinized
B) Transitional epithelium
C) Simple cuboidal epithelium
D) Columnar epithelium

Answer: A) Stratified squamous non-keratinized

Explanation: The distal male urethra transitions to stratified squamous non-keratinized epithelium near the external meatus, suited for protection. Transitional epithelium is proximal, columnar occurs in prostatic urethra, and cuboidal is absent. Thus, A is correct. These changes reflect functional adaptations to urine flow and external exposure.

11) A biopsy shows dome-shaped cells with thickened apical membranes. This finding is typical of–
A) Renal tubules
B) Bladder urothelium
C) Prostate ducts
D) Urethral glands

Answer: B) Bladder urothelium

Explanation: Dome-shaped umbrella cells with thickened apical membranes are characteristic of bladder transitional epithelium. Renal tubules have cuboidal epithelium, prostate ducts columnar epithelium, and urethral glands produce mucus but lack umbrella cells. Thus, B is correct. These surface cells form a protective barrier that adapts to repeated stretch during bladder filling.

Chapter: Physiology; Topic: Renal Physiology; Subtopic: ENaC – Epithelial Sodium Channels

Keyword Definitions:
• ENaC: Epithelial sodium channel responsible for Na⁺ reabsorption in renal collecting ducts and other epithelia.
• Amiloride: Potassium-sparing diuretic that blocks ENaC activity.
• Subunits: ENaC is composed of α, β, and γ regulatory protein subunits.
• Aldosterone: Hormone increasing ENaC expression and sodium reabsorption.
• Principal cells: Renal collecting duct cells where ENaC channels are located.
• GIT epithelium: ENaC also present in colon for sodium absorption.

Lead Question - 2015
True about ENaC are all except ?
a) Epithelial channel
b) Composed of 2 homologous subunits
c) Present in kidney and GIT
d) Inhibited by amiloride

Explanation (Answer: b) Composed of 2 homologous subunits)
ENaC is an epithelial sodium channel composed of three distinct subunits—α, β, and γ, not two homologous subunits. The channel is located in kidney collecting ducts and gastrointestinal tract. It is a major target of aldosterone and is inhibited effectively by amiloride. Its three-subunit composition ensures proper gating and sodium selectivity.

1. ENaC subunits include:
a) α, β, γ
b) α, β
c) β, γ
d) Only α

Explanation (Answer: a) α, β, γ)
ENaC consists of three separate subunits—alpha, beta, and gamma—each contributing to channel structure and function. The α subunit forms the pore, and β and γ regulate gating and surface expression. Mutation in any of these subunits can lead to disorders of sodium handling, volume imbalance, and conditions like Liddle syndrome.

2. ENaC is regulated mainly by:
a) Vasopressin
b) Aldosterone
c) Parathyroid hormone
d) Prolactin

Explanation (Answer: b) Aldosterone)
Aldosterone strongly regulates ENaC by increasing its synthesis and membrane insertion in the collecting duct, enhancing sodium reabsorption and maintaining extracellular volume. Vasopressin influences water reabsorption, not ENaC. Parathyroid hormone regulates calcium, and prolactin has no renal ENaC-related action.

3. ENaC inhibition causes:
a) Hyperkalemia
b) Hypoglycemia
c) Hypercalcemia
d) Hyperphosphatemia

Explanation (Answer: a) Hyperkalemia)
ENaC inhibition reduces Na⁺ entry into principal cells, decreasing the gradient needed for K⁺ secretion, resulting in hyperkalemia. This is seen in pseudohypoaldosteronism and amiloride therapy. Calcium and phosphate levels are not directly linked to ENaC function, and glucose remains unaffected.

4. ENaC overactivity occurs in:
a) Liddle syndrome
b) Gitelman syndrome
c) Bartter syndrome
d) Addison disease

Explanation (Answer: a) Liddle syndrome)
Liddle syndrome is caused by hyperactive ENaC channels, leading to excessive Na⁺ reabsorption, hypertension, hypokalemia, and metabolic alkalosis. Aldosterone levels are low because channel activation is independent. Amiloride effectively blocks channel activity, reversing symptoms and lowering blood pressure.

5. ENaC blockers are classified as:
a) Loop diuretics
b) Thiazides
c) Potassium-sparing diuretics
d) Osmotic diuretics

Explanation (Answer: c) Potassium-sparing diuretics)
Amiloride and triamterene are potassium-sparing diuretics that block ENaC in the collecting duct. They reduce Na⁺ reabsorption without increasing K⁺ excretion. Loop diuretics and thiazides act on upstream segments, while osmotic diuretics alter tubular osmotic gradient but do not affect ENaC.

6. ENaC is primarily expressed in which nephron segment?
a) Proximal tubule
b) Collecting duct
c) Loop of Henle
d) Distal convoluted tubule

Explanation (Answer: b) Collecting duct)
ENaC channels are located in principal cells of the collecting duct, where they fine-tune sodium handling under aldosterone control. Distal convoluted tubule uses Na⁺/Cl⁻ cotransport. Proximal tubule and loop of Henle absorb sodium differently through other transporters and channels.

7. Activity of ENaC increases in:
a) Hypernatremia
b) Hypovolemia
c) Hyperglycemia
d) Edema

Explanation (Answer: b) Hypovolemia)
In hypovolemia, aldosterone secretion increases, stimulating ENaC expression to enhance Na⁺ retention and restore blood volume. ENaC does not directly respond to hypernatremia or hyperglycemia. Edema formation involves hydrostatic pressure and permeability, not specific ENaC activation in kidney.

8. ENaC dysfunction clinically presents as:
a) Severe salt loss
b) Hypercalcemia
c) Metabolic alkalosis only
d) Hypoglycemia

Explanation (Answer: a) Severe salt loss)
Loss-of-function ENaC defects cause salt-wasting disorders such as pseudohypoaldosteronism type 1. Patients develop dehydration, hypotension, hyperkalemia, metabolic acidosis, and hyponatremia. Calcium and glucose levels remain normal. In contrast, ENaC overactivity results in hypertension with hypokalemia.

9. ENaC function depends on:
a) CFTR regulation
b) ADH activation
c) Renin synthesis
d) Glucagon stimulation

Explanation (Answer: a) CFTR regulation)
CFTR regulates ENaC, particularly in airway and intestinal epithelia. CFTR inhibits ENaC; absence of CFTR in cystic fibrosis causes ENaC hyperactivity, thick mucus, and airway obstruction. ADH regulates water via aquaporins, not ENaC. Renin and glucagon do not directly affect ENaC channels.

10. Drug choice in Liddle syndrome:
a) Spironolactone
b) Amiloride
c) Furosemide
d) Hydrochlorothiazide

Explanation (Answer: b) Amiloride)
Amiloride is effective because it directly blocks ENaC hyperactivity in Liddle syndrome. Spironolactone is ineffective because aldosterone levels are already low. Furosemide and thiazides act on different nephron segments and cannot correct ENaC-driven sodium retention, hypertension, or hypokalemia caused by mutated channels.

Chapter: Physiology; Topic: Renal Physiology; Subtopic: Epithelial Sodium Channels (ENaC)

Keyword Definitions:
• Epithelial sodium channel (ENaC): Sodium-selective channel present in renal collecting ducts, lungs, colon, and sweat glands.
• Alpha subunit (α): Functional pore-forming ENaC unit required for channel activation.
• Beta subunit (β): Regulatory subunit modifying channel kinetics and surface stability.
• Gamma subunit (γ): Enhances channel opening probability and increases sodium conductance.
• Aldosterone: Hormone stimulating ENaC synthesis and increasing sodium reabsorption.
• Pseudohypoaldosteronism: Disorder caused by ENaC mutations impairing sodium regulation.

Lead Question – 2015
Epithelial sodium channels has ?
a) 2α, 2β
b) 1α, 1β
c) 2α, 2β, 2γ
d) 2α, 1β, 2γ

Explanation (Answer: c) 2α, 2β, 2γ)
ENaC consists of six subunits assembled as 2α, 2β, 2γ. Each α unit contributes to channel pore structure, while β and γ regulate gating and stability. Channel expression is regulated by aldosterone, enhancing sodium uptake in renal collecting ducts. Dysfunction causes electrolyte imbalance, hyperkalemia, hypotension, and acid-base disorders, highlighting ENaC’s physiological relevance in sodium homeostasis.

1. ENaC channels are primarily located in:
a) Proximal tubule
b) Thick ascending limb
c) Collecting duct
d) Loop of Henle

Explanation (Answer: c) Collecting duct)
ENaC channels are present mainly in the principal cells of the collecting duct, where they control fine sodium reabsorption. Aldosterone increases ENaC expression and activity, affecting sodium retention and potassium secretion. Proximal tubule reabsorbs sodium via other transporters but not ENaC. Collecting duct dysfunction causes salt wasting and volume depletion.

2. Aldosterone increases sodium reabsorption by increasing:
a) Na⁺/K⁺ pump synthesis
b) ENaC channel insertion
c) K⁺ channel activation
d) Water reabsorption alone

Explanation (Answer: b) ENaC channel insertion)
Aldosterone stimulates increased ENaC insertion in collecting duct cell membranes, enhancing sodium reabsorption. It also stimulates Na⁺/K⁺ ATPase activity indirectly. Enhanced sodium uptake increases osmotic water movement. Reduced ENaC response contributes to pseudohypoaldosteronism and impaired sodium conservation in hypovolemic states.

3. Mutation of ENaC leads to:
a) Liddle syndrome
b) Gitelman syndrome
c) Bartter syndrome
d) Diabetes insipidus

Explanation (Answer: a) Liddle syndrome)
Liddle syndrome is caused by gain-of-function mutation of ENaC leading to excessive sodium reabsorption, volume expansion, hypertension, and hypokalemia. Unlike hyperaldosteronism, aldosterone levels are low. Treatment involves amiloride or triamterene, ENaC blockers. Other syndromes affect different segments of renal tubules, not ENaC.

4. Which diuretic blocks ENaC channels?
a) Furosemide
b) Thiazides
c) Amiloride
d) Mannitol

Explanation (Answer: c) Amiloride)
Amiloride blocks ENaC directly, reducing sodium reabsorption and preventing potassium loss. It is used in Liddle syndrome and as potassium-sparing diuretic in hypertension. Furosemide acts on NKCC2 in loop of Henle; thiazides inhibit Na-Cl transport in distal tubule; mannitol increases osmotic diuresis without channel interaction.

5. ENaC activity is highest in which physiological state?
a) Hypernatremia
b) Volume depletion
c) Hyperkalemia
d) Metabolic acidosis

Explanation (Answer: b) Volume depletion)
During volume depletion, aldosterone surges, increasing ENaC synthesis and sodium retention to restore blood volume. Hyperkalemia also stimulates aldosterone but ENaC activation primarily aims to conserve sodium. In metabolic acidosis or hypernatremia, ENaC regulation is not the dominant corrective mechanism.

6. Dysfunction of ENaC results in:
a) Hyponatremia
b) Salt-wasting crisis
c) Hypercalcemia
d) Hypermagnesemia

Explanation (Answer: b) Salt-wasting crisis)
Loss-of-function ENaC mutations cause pseudohypoaldosteronism type I, leading to impaired sodium reabsorption and severe salt-wasting. Symptoms include hypotension, dehydration, hyperkalemia, and metabolic acidosis. Hyponatremia occurs secondarily but core problem is salt loss. Calcium and magnesium levels remain unaffected directly by ENaC dysfunction.

7. ENaC is regulated by which hormone?
a) Vasopressin
b) Aldosterone
c) Cortisol
d) Thyroxine

Explanation (Answer: b) Aldosterone)
Aldosterone is the principal regulator of ENaC. It increases transcription and translation of ENaC subunits and enhances surface expression. Vasopressin affects aquaporins, not ENaC. Cortisol binds glucocorticoid receptors with minimal sodium transport effect, while thyroxine influences metabolism but not direct ENaC regulation.

8. In cystic fibrosis, epithelial sodium channel activity is:
a) Decreased
b) Absent
c) Increased
d) Normal

Explanation (Answer: c) Increased)
In cystic fibrosis, absence of functional CFTR leads to increased ENaC activity, causing excessive sodium and water reabsorption, leading to thick mucus. Hyperactive ENaC worsens airway obstruction. Treatments target airway hydration and correction of mucus viscosity, indirectly reducing ENaC impact on respiratory tissues.

9. ENaC channel malfunction leads to:
a) Hyperkalemia
b) Hypokalemia
c) Hypercalcemia
d) Hypoglycemia

Explanation (Answer: a) Hyperkalemia)
ENaC dysfunction reduces sodium entry into principal cells, lowering electrical gradient needed for potassium secretion. This leads to hyperkalemia, metabolic acidosis, and hypotension in salt-wasting states. Conversely, ENaC hyperactivity in Liddle syndrome can cause hypokalemia due to excessive K⁺ secretion driven by enhanced sodium uptake.

10. ENaC activity is clinically assessed using:
a) Sweat chloride test
b) Blood glucose test
c) Liver function test
d) Thyroid profile

Explanation (Answer: a) Sweat chloride test)
Sweat chloride test identifies CFTR dysfunction, indirectly reflecting ENaC hyperactivity in cystic fibrosis. CFTR normally inhibits ENaC; absence results in excessive sodium uptake, reducing chloride secretion. Elevated sweat chloride indicates defective CFTR, associated with overactive ENaC and thickened secretions.

Chapter: Embryology; Topic: Development of Genitourinary System; Subtopic: Derivatives of Paramesonephric and Mesonephric Ducts

Keyword Definitions:
• Paramesonephric duct (Müllerian duct): Embryonic structure that develops into female genital ducts.
• Mesonephric duct (Wolffian duct): Gives rise to male genital ducts like epididymis and vas deferens.
• Prostatic utricle: A small pouch in males representing the remnant of the Müllerian duct.
• Gartner’s duct: A remnant of the Wolffian duct in females.
• Paraphoron: A vestigial structure in the male genital ridge.
• Trigone of bladder: Formed from the mesonephric ducts, not paramesonephric.

Lead Question - 2015
Which of the following is a derivative of paramesonephric duct in males?
a) Trigone of bladder
b) Paraphoron
c) Prostatic utricle
d) Gartner's duct

Explanation (Answer: c) Prostatic utricle
The paramesonephric ducts regress in males under anti-Müllerian hormone influence, but remnants persist as the prostatic utricle and appendix testis. The prostatic utricle is a small, blind sac in the prostate near the verumontanum, representing the Müllerian duct homologue. Other options derive from mesonephric duct remnants.

1. Which structure in the male represents the remnant of the paramesonephric duct?
a) Epididymis
b) Appendix testis
c) Seminal vesicle
d) Ejaculatory duct

Explanation (Answer: b) Appendix testis
The appendix testis is a small, pedunculated structure on the upper pole of the testis derived from the paramesonephric duct. It is a vestigial remnant similar to the prostatic utricle. The epididymis and ejaculatory ducts originate from the mesonephric duct system, not from the paramesonephric duct.

2. In the male fetus, regression of paramesonephric ducts occurs due to secretion of which hormone?
a) Testosterone
b) Progesterone
c) Anti-Müllerian hormone
d) Estrogen

Explanation (Answer: c) Anti-Müllerian hormone
Sertoli cells of the fetal testes secrete Anti-Müllerian hormone (AMH), also known as Müllerian inhibiting substance. It causes regression of the paramesonephric ducts in male embryos. In its absence, Müllerian derivatives develop, leading to persistence of female internal structures in males.

3. Persistence of the Müllerian duct in a male can result in which clinical condition?
a) Cryptorchidism
b) Persistent Müllerian duct syndrome
c) Hypospadias
d) Testicular feminization

Explanation (Answer: b) Persistent Müllerian duct syndrome)
Persistent Müllerian duct syndrome (PMDS) is caused by deficiency or insensitivity to AMH. Despite a normal male genotype (46,XY) and external genitalia, Müllerian duct structures like uterus and fallopian tubes persist internally. This is a rare cause of cryptorchidism or inguinal hernia in males.

4. Which of the following is a remnant of the mesonephric duct in females?
a) Uterine tube
b) Gartner’s duct
c) Uterus
d) Prostatic utricle

Explanation (Answer: b) Gartner’s duct
Gartner’s duct is a vestigial remnant of the mesonephric (Wolffian) duct in females. It may persist as small cysts along the vaginal wall or broad ligament. The uterine tubes and uterus are paramesonephric derivatives, while the prostatic utricle is a male Müllerian remnant.

5. A 22-year-old male presents with infertility and presence of uterus-like structure on imaging. Which embryological failure explains this finding?
a) Failure of Leydig cell differentiation
b) Failure of AMH secretion
c) Failure of Wolffian duct development
d) Failure of gubernaculum regression

Explanation (Answer: b) Failure of AMH secretion)
Infertility with a uterus-like structure in a genetic male indicates Persistent Müllerian duct syndrome due to failure of Anti-Müllerian hormone (AMH) secretion by Sertoli cells. This results in persistence of Müllerian derivatives like uterus and fallopian tubes despite normal male external genitalia.

6. In females, paramesonephric ducts fuse to form which structure?
a) Urethra
b) Ovaries
c) Uterus
d) Clitoris

Explanation (Answer: c) Uterus)
In females, the paramesonephric (Müllerian) ducts fuse caudally to form the uterus, cervix, and upper part of the vagina. The unfused cranial portions form the uterine tubes. This fusion is crucial for normal uterine development, and its failure leads to uterine anomalies such as septate or bicornuate uterus.

7. Which structure develops from the mesonephric duct in males?
a) Fallopian tube
b) Prostate
c) Vas deferens
d) Appendix testis

Explanation (Answer: c) Vas deferens)
In males, the mesonephric (Wolffian) duct gives rise to the epididymis, vas deferens, ejaculatory duct, and seminal vesicles under the influence of testosterone. The paramesonephric ducts regress except for small remnants such as the prostatic utricle and appendix testis.

8. A 3-year-old boy with undescended testes shows a small midline cyst near the prostate. This is most likely a remnant of which embryonic duct?
a) Mesonephric duct
b) Paramesonephric duct
c) Ureteric bud
d) Allantois

Explanation (Answer: b) Paramesonephric duct)
A small midline cyst near the prostate represents a prostatic utricle cyst, derived from the paramesonephric (Müllerian) duct. These cysts may persist in males due to incomplete regression of Müllerian remnants and may cause urinary or ejaculatory obstruction if large.

9. Which of the following correctly matches the embryonic origin and adult structure?
a) Mesonephric duct – Uterine tube
b) Paramesonephric duct – Epididymis
c) Paramesonephric duct – Uterus
d) Mesonephric duct – Ovary

Explanation (Answer: c) Paramesonephric duct – Uterus)
The paramesonephric duct develops into the uterus, uterine tubes, and upper vagina in females. In males, it largely regresses due to AMH. The mesonephric duct gives rise to male reproductive ducts like vas deferens and seminal vesicle, not to female structures.

10. A male neonate presents with bilateral inguinal hernias and Müllerian duct remnants. Which of the following best explains this condition?
a) Lack of testosterone production
b) Lack of dihydrotestosterone
c) Mutation in AMH gene
d) Mutation in androgen receptor

Explanation (Answer: c) Mutation in AMH gene)
A mutation in the Anti-Müllerian hormone (AMH) gene or its receptor causes Persistent Müllerian duct syndrome. It presents in males with normal external genitalia but persistence of uterus and fallopian tubes, often associated with inguinal hernias or undescended testes due to the Müllerian structures impeding descent.

Chapter: Embryology; Topic: Development of Urinary System; Subtopic: Development of Nephrons and Collecting System

Key Definitions:

• Nephron: The functional unit of the kidney, responsible for filtration, reabsorption, and secretion, composed of the glomerulus, tubules, and loop of Henle.

• Metanephros: The definitive kidney formed from the interaction between the ureteric bud and metanephric mesenchyme.

• Ureteric bud: An outgrowth from the mesonephric duct that gives rise to the ureter, renal pelvis, calyces, and collecting ducts.

• Mesonephros: A transient, intermediate kidney structure that functions temporarily during early embryonic life before the metanephros develops.

Lead Question (NEET PG 2015):

1. Nephron is derived from:

a) Ureteric bud

b) Mesonephric duct

c) Metanephros

d) Mesonephros

Answer: c) Metanephros

Explanation: The nephron, the functional unit of the kidney, develops from the metanephric blastema (metanephric mesenchyme), which arises from the intermediate mesoderm. The metanephric mesenchyme interacts with the ureteric bud to form nephrons, including the glomerulus, proximal tubule, loop of Henle, and distal convoluted tubule. The ureteric bud, on the other hand, forms the collecting system (collecting ducts, calyces, renal pelvis, and ureter). This reciprocal induction between the metanephric blastema and ureteric bud ensures proper nephron differentiation and renal development.

Guessed Questions (Related to Development of Urinary System):

2. The ureteric bud gives rise to all of the following except:

a) Collecting ducts

b) Renal pelvis

c) Loop of Henle

d) Ureter

Answer: c) Loop of Henle

Explanation: The loop of Henle develops from the metanephric mesenchyme, not the ureteric bud. The ureteric bud forms the collecting ducts, calyces, renal pelvis, and ureter, representing the collecting system of the kidney.

3. Clinical: A newborn presents with unilateral renal agenesis. The most likely embryological defect is:

a) Failure of metanephric blastema formation

b) Failure of ureteric bud formation

c) Failure of mesonephric duct development

d) Failure of pronephros formation

Answer: b) Failure of ureteric bud formation

Explanation: Unilateral renal agenesis occurs when the ureteric bud fails to develop or fails to contact the metanephric mesenchyme. As a result, nephron induction does not occur, leading to absence of one kidney.

4. The glomerulus and Bowman’s capsule are derived from:

a) Ureteric bud

b) Metanephric mesenchyme

c) Mesonephric duct

d) Cloaca

Answer: b) Metanephric mesenchyme

Explanation: Both the glomerulus and Bowman’s capsule originate from the metanephric mesenchyme, part of the metanephros. These structures form the filtration barrier crucial for renal function.

5. Clinical: Bilateral renal agenesis leads to which fetal condition?

a) Anencephaly

b) Oligohydramnios

c) Polyhydramnios

d) Hydrocephalus

Answer: b) Oligohydramnios

Explanation: Bilateral renal agenesis results in absence of urine formation, leading to oligohydramnios (reduced amniotic fluid). This causes pulmonary hypoplasia, limb deformities, and facial anomalies, collectively known as Potter sequence.

6. The collecting ducts of the kidney develop from:

a) Metanephric mesenchyme

b) Ureteric bud

c) Mesonephric duct

d) Intermediate mesoderm directly

Answer: b) Ureteric bud

Explanation: The collecting ducts originate from branching of the ureteric bud, which is an outgrowth of the mesonephric duct. This structure ultimately gives rise to the entire collecting system of the kidney.

7. Clinical: A cystic kidney in a newborn is caused by abnormal interaction between:

a) Metanephric blastema and ureteric bud

b) Pronephros and mesonephros

c) Ureter and cloaca

d) Glomerulus and collecting duct

Answer: a) Metanephric blastema and ureteric bud

Explanation: Improper reciprocal induction between the metanephric blastema and ureteric bud leads to polycystic or dysplastic kidneys. This defective signaling results in cystic dilation of renal tubules.

8. The mesonephric duct in males later forms:

a) Vas deferens and epididymis

b) Ureter

c) Prostate gland

d) Urethra

Answer: a) Vas deferens and epididymis

Explanation: The mesonephric (Wolffian) duct develops into male reproductive structures — epididymis, vas deferens, and seminal vesicles. In females, it regresses due to absence of testosterone.

9. Clinical: A child with a duplicated ureter likely had which developmental error?

a) Duplication of ureteric bud

b) Duplicated metanephric blastema

c) Fusion of mesonephric ducts

d) Early closure of cloaca

Answer: a) Duplication of ureteric bud

Explanation: Duplication of the ureteric bud before it contacts the metanephric blastema results in a duplicated ureter. The condition can be asymptomatic or lead to urinary obstruction.

10. The pronephros, mesonephros, and metanephros are derived from which embryonic tissue?

a) Intermediate mesoderm

b) Paraxial mesoderm

c) Lateral plate mesoderm

d) Endoderm

Answer: a) Intermediate mesoderm

Explanation: All three renal systems — pronephros, mesonephros, and metanephros — develop from the intermediate mesoderm. This tissue extends longitudinally along the dorsal body wall and differentiates into structures of the urinary and reproductive systems.

11. Clinical: An infant with Potter sequence most likely has which embryological defect?

a) Bilateral renal agenesis

b) Failure of ureteric bud branching

c) Persistence of pronephros

d) Early closure of cloacal membrane

Answer: a) Bilateral renal agenesis

Explanation: Potter sequence results from severe oligohydramnios due to bilateral renal agenesis. The absence of fetal urine causes pulmonary hypoplasia, limb deformities, and flattened facies — classic features of this syndrome.

Chapter: Anatomy of Female Genital Tract; Topic: Uterine Blood Supply; Subtopic: Sequence of Arterial Branches in the Uterus

Keyword Definitions:

• Uterine artery: Main arterial supply to the uterus, a branch of the internal iliac artery.

• Arcuate artery: Vessels running circumferentially within the myometrium.

• Radial artery: Branches from arcuate arteries that penetrate deep into the myometrium.

• Spiral artery: Terminal branches supplying the endometrium, especially functional layer.

1. Lead Question (NEET PG 2023):

Correct sequence of uterine blood flow -

A) Uterine A → Arcuate A → Radial A → Spiral A

B) Uterine A → Radial A → Arcuate A → Spiral A

C) Uterine A → Spiral A → Radial A → Arcuate A

D) Uterine A → Arcuate A → Spiral A → Radial A

Explanation:

The correct sequence of blood flow in the uterus is from the uterine artery, which gives rise to arcuate arteries within the myometrium. From the arcuate arteries, radial arteries branch inward toward the endometrium and further divide into straight and spiral arteries. Spiral arteries supply the functional layer of the endometrium and undergo cyclical changes during menstruation. Therefore, the correct answer is Option A (Uterine A → Arcuate A → Radial A → Spiral A).

Guessed Questions:

2. The uterine artery is a direct branch of which major artery?

A) External iliac artery

B) Internal iliac artery

C) Common iliac artery

D) Inferior mesenteric artery

Explanation: The uterine artery arises from the anterior division of the internal iliac artery. It supplies the uterus, cervix, and upper vagina and anastomoses with the ovarian artery. Hence, the correct answer is B) Internal iliac artery.

3. Which arteries of the uterus are primarily responsible for cyclic changes during the menstrual cycle?

A) Arcuate arteries

B) Radial arteries

C) Spiral arteries

D) Straight arteries

Explanation: Spiral arteries supply the functional layer of the endometrium and undergo significant changes during the menstrual cycle, including constriction during menstruation leading to endometrial shedding. Thus, the correct answer is C) Spiral arteries.

4. Which layer of the uterus contains arcuate arteries?

A) Endometrium

B) Myometrium

C) Perimetrium

D) Cervical canal

Explanation: The arcuate arteries run circumferentially within the middle layer of the uterus, the myometrium, and give rise to radial arteries that penetrate deeper layers. The correct answer is B) Myometrium.

5. During hysterectomy, uterine artery is closely related to which structure?

A) Ureter

B) Ovary

C) Fallopian tube

D) Round ligament

Explanation: The uterine artery crosses the ureter superiorly near the lateral fornix of the vagina — often remembered as “water under the bridge.” Therefore, care must be taken to avoid ureteric injury. Correct answer is A) Ureter.

6. Which artery forms an anastomosis with the ovarian artery at the uterine cornua?

A) Vaginal artery

B) Internal pudendal artery

C) Uterine artery

D) Inferior vesical artery

Explanation: The uterine artery anastomoses with the ovarian artery at the uterine cornua, ensuring collateral circulation. Hence, the correct answer is C) Uterine artery.

7. (Clinical) A 35-year-old woman with postpartum hemorrhage is undergoing uterine artery ligation. Which of the following best explains the purpose of this procedure?

A) To increase uterine perfusion

B) To reduce blood loss by decreasing uterine arterial flow

C) To improve ovarian blood flow

D) To block venous drainage

Explanation: Uterine artery ligation helps in controlling postpartum hemorrhage by decreasing arterial inflow to the uterus, reducing bleeding while preserving fertility via collateral circulation from ovarian arteries. Thus, correct answer is B) To reduce blood loss by decreasing uterine arterial flow.

8. (Clinical) A patient with Asherman’s syndrome has damage to which vascular structure supplying the endometrium?

A) Arcuate arteries

B) Radial arteries

C) Spiral arteries

D) Straight arteries

Explanation: Asherman’s syndrome involves scarring of the endometrium, primarily affecting spiral arteries that supply the functional layer. The resultant hypoperfusion leads to amenorrhea or infertility. Correct answer: C) Spiral arteries.

9. (Clinical) A 42-year-old woman with fibroids undergoes uterine artery embolization. Which of the following mechanisms is responsible for fibroid shrinkage?

A) Increased perfusion

B) Ischemic necrosis due to reduced arterial supply

C) Venous congestion

D) Hormonal inhibition

Explanation: Uterine artery embolization induces ischemic necrosis by blocking arterial blood flow to fibroids, leading to reduction in size and symptoms. Hence, the correct answer is B) Ischemic necrosis due to reduced arterial supply.

10. (Clinical) A 28-year-old woman with severe dysmenorrhea shows excessive constriction of which arteries leading to ischemic pain?

A) Arcuate arteries

B) Spiral arteries

C) Radial arteries

D) Straight arteries

Explanation: Dysmenorrhea is associated with prostaglandin-mediated constriction of spiral arteries, leading to uterine ischemia and pain. The correct answer is B) Spiral arteries.

11. (Clinical) In placenta accreta, abnormal trophoblastic invasion is primarily due to the absence of which endometrial layer affecting uterine vasculature?

A) Decidua basalis

B) Myometrium

C) Endometrium functional layer

D) Decidua capsularis

Explanation: Placenta accreta occurs when the decidua basalis is absent, allowing chorionic villi to invade the myometrium and its vascular layers. This leads to hemorrhage during delivery. Correct answer: A) Decidua basalis.

Chapter: Abdomen; Topic: Blood Supply of Kidney; Subtopic: Renal Arteries and Veins

Keyword Definitions:

• Renal artery: A branch of the abdominal aorta supplying blood to each kidney.

• Renal vein: The vein that drains deoxygenated blood from the kidney into the inferior vena cava.

• Inferior vena cava (IVC): The large vein that carries blood from the lower body to the heart.

• End arteries: Arteries that do not anastomose with others; blockage leads to tissue necrosis.

• Common iliac artery: A terminal branch of the aorta that divides into external and internal iliac arteries, not supplying the kidney.

Lead Question (2015)
Not True about blood supply of kidney -
a) Renal vein drains into IVC
b) Renal artery is a branch of common iliac artery
c) Right renal artery passes behind IVC
d) Branches of renal artery are end arteries

Explanation: The renal artery arises directly from the abdominal aorta, not from the common iliac artery. The right renal artery passes posterior to the IVC, and both renal arteries divide into end arteries without anastomosis. The renal vein drains into the IVC. Hence, the incorrect statement is (b) Renal artery is a branch of common iliac artery.

1. Which of the following arteries supplies the upper pole of the kidney?
a) Superior suprarenal artery
b) Inferior phrenic artery
c) Renal artery
d) Gonadal artery

Explanation: The superior pole of the kidney receives blood mainly from the renal artery, with minor contributions from the inferior phrenic and superior suprarenal arteries. The gonadal artery does not supply the kidney. Hence, the correct answer is (c) Renal artery.

2. The left renal vein is longer than the right because -
a) It receives more tributaries
b) It crosses anterior to aorta
c) It passes behind IVC
d) It lies higher than right vein

Explanation: The left renal vein is longer because it crosses anterior to the abdominal aorta to reach the IVC and receives tributaries from the left gonadal and suprarenal veins. The right renal vein directly enters the IVC and is shorter. Hence, the answer is (b) It crosses anterior to aorta.

3. Accessory renal arteries arise from -
a) Common iliac artery
b) Abdominal aorta
c) Lumbar arteries
d) Gonadal artery

Explanation: Accessory renal arteries are additional branches that arise directly from the abdominal aorta. They may enter the kidney at poles and are also end arteries, meaning damage may cause ischemia. Hence, the correct answer is (b) Abdominal aorta.

4. During renal transplantation, the donor renal artery is anastomosed to -
a) Common iliac artery
b) External iliac artery
c) Internal iliac artery
d) Inferior epigastric artery

Explanation: In renal transplantation, the donor renal artery is commonly anastomosed to the recipient’s external iliac artery due to easy accessibility and adequate blood flow. Hence, the answer is (b) External iliac artery.

5. The venous drainage of the right suprarenal gland is into -
a) Left renal vein
b) Right renal vein
c) IVC directly
d) Inferior phrenic vein

Explanation: The right suprarenal vein drains directly into the inferior vena cava, while the left suprarenal vein drains into the left renal vein. Hence, the answer is (c) IVC directly.

6. A patient undergoing nephrectomy has bleeding due to injury of a posterior structure to right renal artery. Which is it?
a) IVC
b) Psoas major
c) Right renal vein
d) Diaphragm

Explanation: The right renal artery passes posterior to the IVC before entering the kidney. During surgical dissection, injury to the IVC can cause massive bleeding. Hence, the answer is (a) IVC.

7. Which of the following is an end artery in the kidney?
a) Interlobar artery
b) Arcuate artery
c) Interlobular artery
d) All of the above

Explanation: The segmental, interlobar, arcuate, and interlobular arteries of the kidney are all end arteries without significant anastomoses. Occlusion leads to infarction of supplied areas. Hence, the answer is (d) All of the above.

8. In renal vein thrombosis, which symptom is most likely?
a) Hematuria
b) Hypotension
c) Polyuria
d) Bradycardia

Explanation: Renal vein thrombosis leads to impaired venous drainage causing congestion and rupture of small vessels resulting in hematuria and flank pain. It may also cause renal enlargement and proteinuria. Hence, the answer is (a) Hematuria.

9. The renal artery divides into segmental branches before entering which structure?
a) Hilum
b) Cortex
c) Medulla
d) Capsule

Explanation: The renal artery divides into five segmental branches before entering the hilum of the kidney. Each supplies a specific renal segment without anastomosis, maintaining functional independence. Hence, the answer is (a) Hilum.

10. In CT angiography, a prehilar branch of renal artery is seen compressing the renal pelvis. What condition can result?
a) Hydronephrosis
b) Renal infarction
c) Pyelonephritis
d) Nephrocalcinosis

Explanation: An aberrant prehilar renal artery crossing anterior to the renal pelvis may compress it, causing obstruction of urine flow leading to hydronephrosis, especially in younger patients. Hence, the answer is (a) Hydronephrosis.

Chapter: Abdomen; Topic: Posterior Relations of Kidneys; Subtopic: Surface Anatomy and Relations

Keyword Definitions:

• Kidney: A retroperitoneal organ responsible for urine formation and excretion of metabolic wastes.

• Posterior relation: Structures located behind an organ, important in surgical and anatomical understanding.

• Subcostal nerve: The nerve running below the 12th rib, providing motor and sensory supply to the abdominal wall.

• Ilioinguinal nerve: A branch of the lumbar plexus supplying the skin over the groin and scrotum/labia.

• Diaphragm: The muscular sheet separating the thoracic and abdominal cavities, aiding in respiration.

Lead Question (2015)
Posterior relation of right kidney are all except -
a) Diaphragm
b) Subcostal nerve
c) 11th rib
d) Ilioinguinal nerve

Explanation: The posterior relations of the right kidney include the diaphragm, 12th rib, and muscles like psoas major, quadratus lumborum, and transversus abdominis, along with nerves like subcostal, iliohypogastric, and ilioinguinal. The 11th rib does not relate posteriorly to the right kidney. Hence, the answer is (c) 11th rib.

1. Posterior relations of left kidney include all except -
a) 11th rib
b) 12th rib
c) Psoas major
d) Descending colon

Explanation: The left kidney is related posteriorly to both 11th and 12th ribs, psoas major, quadratus lumborum, and transversus abdominis. The descending colon lies anterior to the kidney, not posteriorly. Hence, the answer is (d) Descending colon.

2. The right kidney lies opposite which vertebral levels?
a) T10–L1
b) T11–L2
c) T12–L3
d) L1–L4

Explanation: The right kidney typically lies lower due to the presence of the liver, extending from T12 to L3 vertebral levels, while the left kidney lies slightly higher (T11–L2). Hence, the answer is (c) T12–L3.

3. Which muscle forms the medial relation of the kidney posteriorly?
a) Transversus abdominis
b) Quadratus lumborum
c) Psoas major
d) Latissimus dorsi

Explanation: The psoas major muscle forms the medial posterior relation of the kidney and plays a role in flexing the thigh at the hip joint. Hence, the answer is (c) Psoas major.

4. The nerve located posterior to both kidneys is -
a) Obturator nerve
b) Iliohypogastric nerve
c) Phrenic nerve
d) Femoral nerve

Explanation: The iliohypogastric nerve runs posterior to both kidneys along with subcostal and ilioinguinal nerves. It arises from L1 and supplies the abdominal wall. Hence, the answer is (b) Iliohypogastric nerve.

5. The structure anterior to the right kidney is -
a) Liver
b) Spleen
c) Stomach
d) Pancreas

Explanation: The anterior relation of the right kidney includes the liver, duodenum, and right colic flexure, while the spleen and stomach relate to the left kidney. Hence, the answer is (a) Liver.

6. A stab injury at the right costovertebral angle injures which structure first?
a) Diaphragm
b) 12th rib
c) Kidney
d) Liver capsule

Explanation: The costovertebral angle corresponds to the posterior relation of the kidney. A stab wound here usually affects the lower part of the kidney first, making it vulnerable to injury. Hence, the answer is (c) Kidney.

7. The upper pole of the right kidney is related to -
a) Liver
b) Spleen
c) Diaphragm
d) Stomach

Explanation: The upper pole of the right kidney lies beneath the diaphragm and is in contact with the right suprarenal gland and the liver. Hence, the answer is (a) Liver.

8. In renal surgeries, posterior approach is preferred because -
a) Avoids peritoneal cavity
b) Provides better exposure of renal hilum
c) Easy access to renal vein
d) Prevents injury to adrenal gland

Explanation: Posterior approach avoids opening the peritoneal cavity, thus minimizing risk of contamination and complications. It also allows direct access to the kidney's posterior surface. Hence, the answer is (a) Avoids peritoneal cavity.

9. During nephrectomy, which nerve may be damaged posteriorly?
a) Obturator
b) Iliohypogastric
c) Phrenic
d) Sciatic

Explanation: The iliohypogastric nerve lies close to the posterior surface of the kidney and can be damaged during posterior incisions or retraction in nephrectomy. Hence, the answer is (b) Iliohypogastric.

10. In a CT scan, the posterior relation of left kidney at the level of 12th rib includes -
a) Diaphragm
b) Liver
c) Duodenum
d) Stomach

Explanation: At the level of the 12th rib, the posterior surface of the left kidney is covered by the diaphragm, quadratus lumborum, and psoas major. Hence, the answer is (a) Diaphragm.

Chapter: Urinary System; Topic: Urinary Bladder; Subtopic: Uvula Vesicae

Keyword Definitions:

• Uvula Vesicae: A small elevation in the posterior part of the bladder, near the internal urethral orifice.

• Prostate Gland: A male accessory gland located below the urinary bladder, surrounding the prostatic urethra.

• Median Lobe: The portion of the prostate between the ejaculatory ducts and urethra, projecting upward beneath the bladder neck.

Lead Question – 2015
Uvula vesicae seen in bladder is formed from the following structure?
a) Median lobe of prostate
b) Lateral lobe of prostate
c) Anterior lobe of prostate
d) Posterior lobe of prostate

Explanation: The uvula vesicae is formed by the submucosal projection produced by the enlargement of the median lobe of the prostate beneath the internal urethral orifice. It plays a role in controlling urinary flow by closing the urethral opening during ejaculation. Hypertrophy of this lobe may obstruct urine flow in elderly males. Hence, the correct answer is a) Median lobe of prostate.

1. The trigone of urinary bladder is derived from:
a) Mesonephric ducts
b) Metanephros
c) Ureteric bud
d) Cloaca

Explanation: The trigone of the bladder develops from the mesonephric ducts, while the rest of the bladder is endodermal in origin from the urogenital sinus. Initially, it is mesodermal but becomes endodermal due to mucosal overgrowth. The trigone region is smooth and non-contractile. Thus, the correct answer is a) Mesonephric ducts.

2. Which artery supplies the superior surface of the urinary bladder?
a) Superior vesical artery
b) Inferior vesical artery
c) Middle rectal artery
d) Internal pudendal artery

Explanation: The superior vesical artery, a branch of the umbilical artery, supplies the upper surface of the bladder. The inferior vesical artery (in males) and vaginal artery (in females) supply the base. These arteries provide vital oxygen and nutrients for bladder wall contraction. Correct answer: a) Superior vesical artery.

3. Clinical case: A 70-year-old male presents with urinary obstruction. The likely cause is hypertrophy of which lobe of the prostate?
a) Median lobe
b) Lateral lobe
c) Anterior lobe
d) Posterior lobe

Explanation: In elderly men, benign prostatic hyperplasia primarily affects the median lobe located beneath the bladder neck. Its enlargement compresses the urethra and causes urinary retention, frequency, and dribbling. Surgical removal of the hypertrophied lobe relieves obstruction. Thus, the correct answer is a) Median lobe.

4. Nerve supply to the urinary bladder includes all EXCEPT:
a) Pelvic splanchnic nerves
b) Hypogastric plexus
c) Pudendal nerve
d) Femoral nerve

Explanation: The bladder receives parasympathetic fibers from pelvic splanchnic nerves (S2-S4), sympathetic fibers from the hypogastric plexus, and somatic fibers from the pudendal nerve. The femoral nerve has no role in bladder control. Thus, the correct answer is d) Femoral nerve.

5. Clinical case: A male with prostate cancer shows invasion into the bladder base. Which area is most affected?
a) Trigone
b) Dome
c) Uvula vesicae
d) Neck

Explanation: In prostate carcinoma, the uvula vesicae and adjacent trigone are often invaded due to close anatomical proximity. This results in urinary obstruction and hematuria. The bladder base lies directly above the prostate, making it prone to infiltration. Thus, the correct answer is c) Uvula vesicae.

6. Which muscle helps to expel the last drops of urine during micturition?
a) Detrusor muscle
b) Compressor urethrae
c) Bulbospongiosus
d) External urethral sphincter

Explanation: The bulbospongiosus muscle aids in expelling the last drops of urine and semen by rhythmic contraction. It surrounds the bulb of the penis and contributes to urethral emptying after bladder contraction. The detrusor muscle empties the main volume, while bulbospongiosus clears the residue. Correct answer: c) Bulbospongiosus.

7. The epithelial lining of urinary bladder is:
a) Simple columnar
b) Stratified squamous
c) Transitional epithelium
d) Pseudostratified columnar

Explanation: The bladder is lined by transitional epithelium (urothelium) that stretches to accommodate varying urine volumes. It appears cuboidal when relaxed and squamous when distended. This flexibility prevents leakage and maintains barrier integrity. Correct answer: c) Transitional epithelium.

8. Clinical case: Pain from bladder distension is referred to which region?
a) Suprapubic
b) Umbilical
c) Epigastric
d) Perineal

Explanation: Bladder distension pain is referred to the suprapubic region due to afferent fibers traveling with pelvic splanchnic nerves (S2-S4). These fibers project to the same dermatomes, producing suprapubic discomfort. Correct answer: a) Suprapubic.

9. The internal urethral sphincter is made up of:
a) Skeletal muscle
b) Smooth muscle
c) Elastic tissue
d) Fibrous tissue

Explanation: The internal urethral sphincter consists of smooth muscle located at the neck of the bladder. It prevents retrograde ejaculation by closing during semen emission. Being involuntary, it is under sympathetic control. Correct answer: b) Smooth muscle.

10. Clinical case: A patient complains of continuous dribbling of urine after prostate surgery. The structure likely damaged is:
a) Internal urethral sphincter
b) External urethral sphincter
c) Detrusor muscle
d) Uvula vesicae

Explanation: The external urethral sphincter provides voluntary control of urination. Injury during prostatectomy leads to urinary incontinence manifested as dribbling. The internal sphincter maintains continence at rest, but voluntary control is lost when the external one is damaged. Correct answer: b) External urethral sphincter.

Chapter: Pelvis and Perineum; Topic: Rectum; Subtopic: Relations of the Rectum

Keyword Definitions:

• Rectum: The terminal part of the large intestine that stores feces before defecation.

• Rectovesical pouch: A peritoneal reflection between the rectum and the urinary bladder in males.

• Seminal Vesicle: Paired glands posterior to the bladder producing seminal fluid.

• Ductus Deferens: A muscular tube conveying sperm from epididymis to ejaculatory duct.

• Sacrum: Large triangular bone forming posterior wall of pelvis.

Lead Question – 2015

Anterior relation to upper part of rectum in male is –

a) Rectovesical pouch

b) Sacrum

c) Seminal vesicle

d) Ductus deferens

Explanation:

The upper one-third of the rectum in males is covered anteriorly by peritoneum reflected onto the bladder, forming the rectovesical pouch. This pouch may contain loops of the small intestine or sigmoid colon. It is the most dependent part of the peritoneal cavity in males when supine. The correct answer is a) Rectovesical pouch. (100 words)

1. The posterior relation of the upper part of the rectum is –

a) Sacrum and coccyx

b) Bladder

c) Prostate

d) Ureter

Explanation:

The posterior aspect of the rectum throughout its length is related to the concavity of the sacrum and coccyx. It lies over the median sacral vessels and sympathetic trunks. The presacral fascia separates the rectum from these structures. This relation helps surgeons identify the presacral venous plexus during pelvic operations. The correct answer is a) Sacrum and coccyx. (100 words)

2. Which structure lies anterior to the lower third of rectum in males?

a) Prostate gland

b) Seminal vesicle

c) Rectovesical pouch

d) Urinary bladder

Explanation:

The anterior relation of the lower third of the rectum in males is the prostate gland and the posterior surface of the urethra. This part of the rectum is devoid of peritoneal covering and is separated from the prostate by the rectovesical fascia (Denonvilliers’ fascia). Digital rectal examination often assesses prostate health. The correct answer is a) Prostate gland. (100 words)

3. In females, the peritoneal reflection between rectum and uterus is called –

a) Rectouterine pouch (Pouch of Douglas)

b) Vesicouterine pouch

c) Rectovesical pouch

d) Pararectal fossa

Explanation:

In females, the peritoneal reflection between the rectum and uterus forms the rectouterine pouch, also known as the Pouch of Douglas. It is the lowest point of the peritoneal cavity in standing position and a common site for fluid collection, such as pus or blood. The correct answer is a) Rectouterine pouch (Pouch of Douglas). (100 words)

4. The lowest part of the peritoneal cavity in males when standing is –

a) Rectovesical pouch

b) Paracolic gutter

c) Hepatorenal pouch

d) Vesicouterine pouch

Explanation:

In males, the rectovesical pouch lies between the rectum and urinary bladder and forms the lowest part of the peritoneal cavity when standing upright. Any intraperitoneal fluid or pus tends to accumulate here, which can be clinically drained through the anterior rectal wall. The correct answer is a) Rectovesical pouch. (100 words)

5. The middle third of the rectum in males is related anteriorly to –

a) Seminal vesicles and ductus deferens

b) Rectovesical pouch

c) Prostate gland

d) Urinary bladder

Explanation:

The anterior relation of the middle third of the rectum in males is the seminal vesicles and the terminal parts of the ductus deferens. This portion is not covered by peritoneum. These structures lie within the rectovesical fascia. Understanding this anatomy helps prevent damage to reproductive organs during rectal or pelvic surgeries. The correct answer is a) Seminal vesicles and ductus deferens. (100 words)

6. (Clinical) During rectal examination, a firm swelling felt anteriorly through rectal wall in a male most likely involves –

a) Prostate gland

b) Coccyx

c) Seminal vesicle

d) Rectal wall only

Explanation:

A firm swelling palpable through the anterior rectal wall in a male is most commonly the prostate gland. It is examined digitally via the rectum to assess its size, consistency, and surface. Enlargement or nodularity may indicate benign prostatic hypertrophy or carcinoma. The correct answer is a) Prostate gland. (100 words)

7. (Clinical) A patient with pelvic peritonitis in males would accumulate fluid in –

a) Rectovesical pouch

b) Rectouterine pouch

c) Pararectal fossa

d) Ischiorectal fossa

Explanation:

In males, the most dependent peritoneal recess is the rectovesical pouch, lying between the rectum and urinary bladder. Any intraperitoneal infection or rupture of an abdominal viscus may lead to pus or fluid collecting here. It can be drained via the rectum without opening the abdominal cavity. The correct answer is a) Rectovesical pouch. (100 words)

8. (Clinical) Rectal carcinoma involving the upper part of rectum may spread to which peritoneal space first?

a) Rectovesical pouch

b) Paracolic gutter

c) Vesicouterine pouch

d) Hepatorenal pouch

Explanation:

Carcinoma of the upper part of the rectum can infiltrate through the peritoneum into the rectovesical pouch in males or rectouterine pouch in females. These spaces are the most dependent areas of the peritoneal cavity where malignant cells or ascitic fluid may collect. The correct answer is a) Rectovesical pouch. (100 words)

9. (Clinical) During surgery, the rectovesical pouch is approached by –

a) Incision through the peritoneum between bladder and rectum

b) Posterior incision near sacrum

c) Cutting prostate capsule

d) Opening anal canal

Explanation:

To access the rectovesical pouch surgically, an incision is made through the peritoneum located between the posterior surface of the bladder and the anterior surface of the rectum. This approach allows drainage of abscesses or fluids without disturbing other pelvic viscera. The correct answer is a) Incision through peritoneum between bladder and rectum. (100 words)

10. (Clinical) A man with peritoneal fluid collection in the pelvis is positioned head down (Trendelenburg). The fluid will move away from –

a) Rectovesical pouch

b) Subphrenic space

c) Hepatorenal pouch

d) Pelvic cavity

Explanation:

In the Trendelenburg position, the head is lower than the pelvis, causing peritoneal fluid to flow from the pelvic cavity toward the upper abdomen. This maneuver moves fluid away from the rectovesical pouch and aids in pelvic surgeries by displacing intestines upward. The correct answer is a) Rectovesical pouch. (100 words)

Chapter: Pelvis;   Topic: Arterial Supply of Pelvic Organs;   Subtopic: Uterine Artery and Its Relations 

Keyword Definitions: 

• Uterine Artery: Main artery supplying the uterus, cervix, and upper vagina, derived from the internal iliac artery. 

• Internal Iliac Artery: Major pelvic artery supplying reproductive organs, bladder, rectum, and muscles. 

• Ovarian Artery: A branch from the abdominal aorta supplying the ovaries and anastomosing with the uterine artery. 

• Ureter: A muscular tube that conveys urine from the kidney to the bladder, crossing under the uterine artery (“water under the bridge”). 

• Parametrium: Connective tissue surrounding the uterus, containing uterine vessels and lymphatics. 

Lead Question - 2015

The uterine artery is a branch of which of the following?

a) Left common iliac artery

b) Internal iliac artery

c) Internal pudendal artery

d) Ovarian artery

Explanation: The uterine artery arises from the anterior division of the internal iliac artery. It ascends along the lateral wall of the pelvis, crosses the ureter (posteriorly), and reaches the uterus at the level of the cervix. It supplies the uterus, upper vagina, and anastomoses with the ovarian artery. Answer: Internal iliac artery.

1. The uterine artery crosses which structure near the lateral fornix?

a) Round ligament

b) Ureter

c) Ovarian ligament

d) Broad ligament

Explanation: The uterine artery crosses the ureter approximately 2 cm lateral to the cervix. The relation is remembered as “water (ureter) under the bridge (uterine artery).” This is a key surgical landmark during hysterectomy to prevent ureteric injury. Answer: Ureter.

2. The uterine artery enters the uterus at the level of:

a) Fundus

b) Body

c) Cervix

d) Isthmus

Explanation: The uterine artery enters the uterus at the level of the cervix, within the broad ligament. From there, it ascends tortuously along the uterine margin to reach the fundus and supplies the myometrium and endometrium. Answer: Cervix.

3. A 35-year-old woman undergoes hysterectomy. During surgery, the uterine artery must be ligated carefully to avoid injury to:

a) Ureter

b) Internal pudendal artery

c) Vaginal artery

d) Ovarian vein

Explanation: During hysterectomy, the uterine artery is tied close to the uterus to avoid accidental ligation of the ureter, which passes inferior to the artery. Ureteric injury can cause urinary leakage and flank pain postoperatively. Answer: Ureter.

4. The uterine artery gives rise to which branch that supplies the upper vagina?

a) Cervical branch

b) Vaginal branch

c) Vesical branch

d) Ovarian branch

Explanation: The vaginal branch of the uterine artery descends to supply the upper part of the vagina. It anastomoses with the vaginal artery from the internal iliac. This dual blood supply is vital during childbirth and uterine surgeries. Answer: Vaginal branch.

5. In angiography, the uterine artery can be identified by its:

a) Straight course to uterus

b) Tortuous path along uterus

c) Branch from posterior division of internal iliac

d) Branching to ovary only

Explanation: The uterine artery follows a tortuous course along the lateral surface of the uterus to accommodate uterine enlargement during pregnancy. On angiography, this spiral pattern distinguishes it from other pelvic arteries. Answer: Tortuous path along uterus.

6. A postpartum woman has heavy bleeding. Embolization of which artery is most effective?

a) Ovarian artery

b) Internal iliac artery

c) Uterine artery

d) Vaginal artery

Explanation: Uterine artery embolization effectively controls postpartum hemorrhage or fibroid-related bleeding. Blocking its flow reduces uterine perfusion, leading to clot formation without compromising fertility if collateral circulation remains intact. Answer: Uterine artery.

7. The uterine artery anastomoses with which artery near the uterine tube?

a) Vaginal artery

b) Ovarian artery

c) Pudendal artery

d) Inferior vesical artery

Explanation: Near the uterine tube, the uterine artery forms an anastomosis with the ovarian artery. This connection ensures continuous uterine blood flow, especially during pregnancy, even if one artery is compromised. Answer: Ovarian artery.

8. The uterine artery is derived from which embryonic artery?

a) Umbilical artery

b) Fourth lumbar artery

c) Common iliac artery

d) Median sacral artery

Explanation: Embryologically, the uterine artery originates from the umbilical artery as a secondary branch of the internal iliac system. This relation explains its origin from the anterior division of the internal iliac artery in adults. Answer: Umbilical artery.

9. A fibroid in the uterus may cause increased flow through which vessel?

a) Uterine artery

b) Vaginal artery

c) Ovarian artery

d) Pudendal artery

Explanation: Fibroids (leiomyomas) are vascular tumors drawing excessive blood through the uterine artery. Doppler imaging shows increased uterine flow, which can contribute to menorrhagia. Answer: Uterine artery.

10. During cesarean section, ligation of the uterine artery is done where?

a) Below the level of the cervix

b) Above the level of the cervix

c) At the fundus

d) Near the ovarian ligament

Explanation: During cesarean section, the uterine artery is ligated just above the cervix to control bleeding while preserving ovarian circulation. This prevents postpartum hemorrhage without damaging vital pelvic structures. Answer: Above the level of the cervix.

11. A 40-year-old woman with fibroids undergoes uterine artery embolization. Which artery’s catheterization is performed?

a) Internal iliac artery

b) External iliac artery

c) Ovarian artery

d) Common femoral artery

Explanation: In uterine artery embolization, access is gained via the common femoral artery, advancing the catheter into the internal iliac artery and then into the uterine artery. Tiny embolic particles block the blood flow to fibroids, causing their shrinkage. Answer: Internal iliac artery.

Chapter: Urogenital System; Topic: Male Urethra; Subtopic: Parts of Male Urethra

Keyword Definitions:

• Male urethra: A fibromuscular tube about 18–20 cm long that conducts urine and semen to the exterior.

• Prostatic urethra: The widest part, passing through the prostate gland.

• Membranous urethra: The shortest and narrowest part, passing through the urogenital diaphragm.

• Spongy (penile) urethra: The longest part passing through the corpus spongiosum of the penis.

Lead Question – 2015

Shortest part of male urethra is:

a) Prostatic

b) Membranous

c) Bulbar

d) Penile

Explanation: The membranous urethra is the shortest and least dilatable portion of the male urethra, measuring about 1.5–2 cm. It lies between the apex of the prostate and the bulb of the penis, passing through the deep perineal pouch surrounded by the external urethral sphincter. Correct answer: (b) Membranous.

1. The longest part of the male urethra is:

a) Prostatic

b) Membranous

c) Spongy

d) Bulbar

Explanation: The spongy (penile) urethra is the longest portion, measuring about 15 cm, running through the corpus spongiosum of the penis. It opens at the external urethral meatus and serves as a common passage for urine and semen. Correct answer: (c) Spongy.

2. The urethral crest is found in which part of the urethra?

a) Prostatic

b) Membranous

c) Penile

d) Bulbar

Explanation: The urethral crest is a vertical ridge in the posterior wall of the prostatic urethra. It contains the prostatic utricle and ejaculatory ducts on either side, forming the seminal colliculus. It plays a role in preventing retrograde ejaculation. Correct answer: (a) Prostatic.

3. During catheterization, resistance is commonly felt at:

a) Prostatic urethra

b) Membranous urethra

c) Bulbar urethra

d) External meatus

Explanation: The greatest resistance during catheterization is at the membranous urethra due to its narrow lumen and passage through the urogenital diaphragm. Improper catheter insertion may cause injury or stricture formation here. Correct answer: (b) Membranous.

4. A 40-year-old man develops urine leakage after perineal injury. The rupture likely involves:

a) Prostatic urethra

b) Membranous urethra

c) Spongy urethra

d) External urethral sphincter

Explanation: Trauma to the perineum, especially from a fall on a hard object, may rupture the spongy (bulbar) urethra. Urine and blood extravasate into the superficial perineal pouch and scrotum but not the thigh due to fascial attachments. Correct answer: (c) Spongy urethra.

5. External urethral sphincter surrounds which part of the urethra?

a) Prostatic

b) Membranous

c) Penile

d) Bulbar

Explanation: The external urethral sphincter (sphincter urethrae) encircles the membranous urethra within the deep perineal pouch. It is composed of skeletal muscle fibers under voluntary control supplied by the pudendal nerve. Correct answer: (b) Membranous.

6. A patient presents with urine leakage into the pelvis after a pelvic fracture. The likely site of rupture is:

a) Prostatic urethra

b) Membranous urethra

c) Bulbar urethra

d) Penile urethra

Explanation: Pelvic fractures commonly disrupt the membranous urethra as it is fixed between the prostate and the perineal membrane. Urine extravasates into the deep perineal pouch and pelvis. Correct answer: (b) Membranous urethra.

7. The ejaculatory ducts open into:

a) Urethral crest

b) Prostatic utricle

c) Seminal colliculus

d) Bulbar urethra

Explanation: The paired ejaculatory ducts pierce the posterior wall of the prostate and open on either side of the prostatic utricle within the seminal colliculus. This allows semen to enter the prostatic urethra during ejaculation. Correct answer: (c) Seminal colliculus.

8. In urethral stricture disease, which part is most commonly affected?

a) Prostatic

b) Membranous

c) Bulbar

d) Penile

Explanation: The bulbar urethra is the most common site for stricture formation following trauma, infection, or instrumentation. The curvature and narrow lumen make it susceptible to fibrosis and scarring. Correct answer: (c) Bulbar.

9. Which part of the urethra receives ducts of bulbourethral glands?

a) Prostatic

b) Membranous

c) Bulbar

d) Penile

Explanation: The bulbourethral glands (Cowper’s glands) open into the proximal spongy urethra near the bulb. Their secretion lubricates the urethra and neutralizes acidity before ejaculation. Correct answer: (c) Bulbar.

10. A male patient develops urine in the scrotum after straddle injury. Urine spread is limited by:

a) Colles’ fascia attachments

b) Deep perineal fascia

c) Buck’s fascia

d) Dartos fascia

Explanation: In bulbar urethral rupture, urine collects in the superficial perineal pouch and scrotum, limited by Colles’ fascia which prevents spread into the thigh. Correct answer: (a) Colles’ fascia attachments.

Chapter: Urology; Topic: Urinary System; Subtopic: Collecting Duct System

Keyword Definitions:

• Collecting Duct: The final part of the nephron system that drains urine from nephrons into the renal pelvis.

• Duct of Bellini: The terminal collecting ducts located in the renal papilla, where multiple smaller collecting ducts merge before opening into the minor calyx.

• Nephron: The functional unit of the kidney responsible for filtration, reabsorption, and secretion.

• Renal Papilla: The tip of the renal pyramid that projects into the minor calyx, delivering urine into the renal pelvis.

Lead Question - 2014
Duct of Bellini are present in:
a) Pancreas
b) Liver
c) Kidney
d) Salivary gland

Answer & Explanation: c) Kidney. The ducts of Bellini are the terminal collecting ducts in the medullary region of the kidney that open into the minor calyces at the tips of the renal papillae. They collect urine from multiple smaller collecting ducts and channel it toward the renal pelvis. These ducts play a vital role in concentrating urine and maintaining electrolyte balance within the nephron system. Their epithelial lining transitions from simple cuboidal to columnar cells near the papilla, aiding final urine modification and water reabsorption.

1. The Duct of Bellini opens into which structure?
a) Minor calyx
b) Major calyx
c) Renal cortex
d) Renal capsule
Answer & Explanation: a) Minor calyx. The Ducts of Bellini open directly into the minor calyces through the renal papilla, allowing urine to pass into the collecting system for excretion. They serve as the final conduit for urine produced by nephrons and are crucial in maintaining fluid concentration and kidney function through regulated water reabsorption.

2. Which type of epithelium lines the Duct of Bellini?
a) Stratified squamous
b) Simple cuboidal
c) Simple columnar
d) Transitional
Answer & Explanation: c) Simple columnar. The terminal collecting ducts (Ducts of Bellini) are lined by simple columnar epithelium, specialized for water and ion transport. This lining facilitates final urine concentration under hormonal control, particularly by antidiuretic hormone (ADH), ensuring osmotic balance and efficient renal excretory function in humans.

3. Which part of the nephron drains into the Duct of Bellini?
a) Distal convoluted tubule
b) Loop of Henle
c) Cortical collecting duct
d) Bowman’s capsule
Answer & Explanation: c) Cortical collecting duct. The cortical collecting ducts converge to form larger medullary ducts, which further merge into the Ducts of Bellini. These structures are crucial for the final concentration of urine and maintenance of electrolyte homeostasis, under hormonal influence such as aldosterone and ADH regulation.

4. Which hormone acts on the Duct of Bellini to promote water reabsorption?
a) Aldosterone
b) ADH
c) ANP
d) Cortisol
Answer & Explanation: b) ADH. Antidiuretic hormone increases the permeability of the Duct of Bellini to water by stimulating aquaporin channels in the epithelial cells. This mechanism conserves water during dehydration and helps maintain osmotic balance, making the collecting ducts key effectors in the hormonal regulation of kidney function.

5. The Duct of Bellini is located in which part of the kidney?
a) Cortex
b) Outer medulla
c) Inner medulla
d) Renal capsule
Answer & Explanation: c) Inner medulla. The Ducts of Bellini run through the inner medulla and terminate at the renal papilla. They represent the final collecting portion of the nephron system, concentrating urine as it passes toward the calyces. Their deep medullary location ensures effective osmotic gradient utilization for water reabsorption.

6. A biopsy from renal papilla shows columnar cells with distinct borders and few intercalated cells. The structure most likely is:
a) Proximal convoluted tubule
b) Loop of Henle
c) Duct of Bellini
d) Collecting duct
Answer & Explanation: c) Duct of Bellini. Histologically, the Duct of Bellini exhibits tall columnar cells with well-defined borders and limited intercalated cells, marking the terminal portion of the collecting duct system. These ducts drain urine into the calyceal system and show adaptations for osmotic water conservation in response to hormonal cues.

7. A patient with a defect in aquaporin-2 channels will have impaired function in which renal structure?
a) Loop of Henle
b) Duct of Bellini
c) Proximal tubule
d) Glomerulus
Answer & Explanation: b) Duct of Bellini. Aquaporin-2 water channels are located in the principal cells of the Duct of Bellini and other collecting ducts. Mutations or deficiencies lead to nephrogenic diabetes insipidus, characterized by inability to concentrate urine despite adequate ADH levels, resulting in excessive dilute urine output and dehydration risk.

8. In chronic renal papillary necrosis, which structure is primarily destroyed?
a) Loop of Henle
b) Glomerulus
c) Duct of Bellini
d) Macula densa
Answer & Explanation: c) Duct of Bellini. Papillary necrosis leads to ischemic destruction of the papilla and associated Ducts of Bellini, causing impaired urine drainage and obstruction. This condition often arises from diabetic nephropathy, analgesic abuse, or severe pyelonephritis, and clinically presents with hematuria, flank pain, and sloughed papillary tissue in urine.

9. In kidney physiology, the Duct of Bellini contributes mainly to:
a) Filtration
b) Secretion of ions
c) Urine concentration
d) Protein synthesis
Answer & Explanation: c) Urine concentration. The Ducts of Bellini, under ADH influence, control final water reabsorption and osmotic concentration of urine before excretion. They ensure body fluid homeostasis by allowing variable water retention, contributing significantly to the kidney’s counter-current mechanism and fine-tuning of electrolyte composition in urine output.

10. Duct of Bellini drains into which structure ultimately?
a) Major calyx
b) Minor calyx
c) Renal cortex
d) Pelvic ureter
Answer & Explanation: b) Minor calyx. The Ducts of Bellini open directly into the minor calyces at the renal papillae, marking the termination point of the nephron system. This direct anatomical connection ensures efficient urine drainage from the kidney into the collecting system, maintaining smooth excretory flow toward the bladder for elimination.

Chapter: Embryology; Topic: Development of Urogenital System; Subtopic: Development of Kidney

Keyword Definitions:

• Ureteric Bud: An outgrowth from the mesonephric duct that forms the collecting system of the kidney.

• Metanephros: The permanent kidney that appears in the fifth week of development.

• Nephron: The functional filtration unit of the kidney derived from metanephric blastema.

• Pronephros and Mesonephros: Primitive kidneys that function temporarily during early embryonic life.

Lead Question - 2014
Excretory system of kidney is derived from?
a) Ureteric bud
b) Mesonephros
c) Metanephros
d) None

Explanation:
The excretory system of the kidney, including nephrons, originates from the metanephric mesoderm (metanephros), while the collecting ducts, calyces, pelvis, and ureter arise from the ureteric bud. Metanephros appears by the 5th week and becomes the permanent kidney. Hence, the correct answer is c) Metanephros.

1. Which part of the kidney develops from the ureteric bud?
a) Glomerulus
b) Collecting ducts
c) Bowman’s capsule
d) Loop of Henle

Explanation:
The ureteric bud gives rise to the collecting ducts, renal pelvis, major and minor calyces, and ureter. The excretory units, including the glomerulus and nephron tubules, come from the metanephric mesenchyme. Therefore, the correct answer is b) Collecting ducts.

2. The metanephric blastema contributes to the formation of:
a) Collecting ducts
b) Nephrons
c) Ureter
d) Pelvis

Explanation:
The metanephric blastema differentiates into nephrons including Bowman’s capsule, proximal tubule, loop of Henle, and distal convoluted tubule. It interacts with the ureteric bud to form the complete kidney structure. Hence, the answer is b) Nephrons.

3. Clinical: A neonate presents with bilateral renal agenesis. Which embryological structure failed to develop?
a) Pronephros
b) Ureteric bud
c) Mesonephros
d) Metanephric blastema

Explanation:
Bilateral renal agenesis occurs due to the failure of the ureteric bud to form or interact with the metanephric blastema. This leads to the absence of both kidneys and causes oligohydramnios (Potter’s sequence). The correct answer is b) Ureteric bud.

4. The ureter develops from:
a) Metanephric blastema
b) Mesonephros
c) Ureteric bud
d) Wolffian duct

Explanation:
The ureter develops as a continuation of the ureteric bud, which sprouts from the Wolffian duct. This bud elongates and differentiates to form the ureter, pelvis, and collecting system of the kidney. Thus, the correct answer is c) Ureteric bud.

5. Clinical: Hydronephrosis in a fetus results mainly due to obstruction in which embryonic derivative?
a) Ureteric bud
b) Metanephros
c) Pronephros
d) Mesonephric duct

Explanation:
Hydronephrosis is caused by obstruction in the ureter or collecting system, which are derivatives of the ureteric bud. Obstruction prevents urine outflow, leading to dilatation of renal pelvis and calyces. Therefore, the correct answer is a) Ureteric bud.

6. Pronephros in humans is:
a) Functional
b) Non-functional
c) Forms nephrons
d) Gives rise to ureter

Explanation:
Pronephros is the first and most primitive form of the kidney in human embryology. It appears early in the 4th week and is non-functional, regressing completely. Hence, the correct answer is b) Non-functional.

7. Clinical: A child with duplicated ureter likely had abnormal branching of which embryonic structure?
a) Mesonephric duct
b) Metanephric blastema
c) Ureteric bud
d) Cloaca

Explanation:
Duplicated ureter occurs due to early division or duplication of the ureteric bud. Each branch may induce separate regions of metanephric tissue, forming two ureters or pelves. Thus, the answer is c) Ureteric bud.

8. Mesonephros contributes to formation of:
a) Testis
b) Kidney
c) Urethra
d) Ovarian follicle

Explanation:
Mesonephros acts as a temporary excretory organ in embryos and contributes to the formation of genital structures such as efferent ducts in males and vestigial remnants in females. Thus, the correct answer is a) Testis.

9. Clinical: Horseshoe kidney results from fusion of the:
a) Ureteric buds
b) Lower poles of metanephric blastema
c) Mesonephric ducts
d) Cloaca

Explanation:
Horseshoe kidney forms when the lower poles of metanephric blastema fuse before ascent. During ascent, the fused kidney gets trapped under the inferior mesenteric artery. The correct answer is b) Lower poles of metanephric blastema.

10. The collecting tubules of kidney arise from:
a) Ureteric bud
b) Metanephric blastema
c) Mesonephros
d) Cloacal membrane

Explanation:
Collecting tubules develop as terminal branches of the ureteric bud. These tubules connect with the distal ends of nephrons derived from the metanephric blastema, allowing urine drainage. Therefore, the correct answer is a) Ureteric bud.

Topic: Renal Circulation; Subtopic: Blood Supply of Kidney in Fetal and Neonatal Life

Keyword Definitions:

• Renal Artery: Major artery supplying blood to the kidney, usually arising from the abdominal aorta.

• Common Iliac Artery: Terminal branch of the aorta that divides into internal and external iliac arteries.

• Fetal Circulation: The circulatory system in the fetus, which includes temporary vessels like the umbilical arteries.

• Neonate: A newborn child, especially within the first 28 days after birth.

Lead Question – 2014

In a neonate, kidney is supplied by?

a) Internal pudendal artery

b) External iliac artery

c) Common iliac artery

d) Aorta

Explanation:

In the neonate, the kidney receives its blood supply from the common iliac artery. During embryonic development, the kidneys ascend from the pelvic region to the lumbar region, and their arterial supply changes from the common iliac to the aorta. However, in neonates, remnants of this early pattern persist temporarily before stabilization occurs. Thus, the answer is common iliac artery.

1. During fetal development, the kidneys receive blood supply from which arteries initially?

a) Umbilical arteries

b) Common iliac arteries

c) Internal iliac arteries

d) Median sacral artery

2. Which of the following statements about the development of renal arteries is true?

a) They arise from the thoracic aorta initially

b) They remain constant in position during development

c) They change position as kidneys ascend

d) They arise from internal iliac arteries permanently

3. A 1-month-old infant presents with an accessory renal artery. This is due to:

a) Persistence of embryonic vessels

b) Renal agenesis

c) Congenital adrenal hyperplasia

d) Malrotation of kidney

4. The final arterial supply of adult kidneys originates from:

a) Common iliac artery

b) Abdominal aorta

c) External iliac artery

d) Median sacral artery

5. Which artery directly gives rise to segmental arteries in the kidney?

a) Interlobar artery

b) Renal artery

c) Afferent arteriole

d) Arcuate artery

6. In fetal life, the kidneys are located in which region?

a) Pelvic region

b) Lumbar region

c) Thoracic region

d) Sacral region

7. A neonate’s renal artery originates lower than normal. What does this indicate?

a) Incomplete renal ascent

b) Polycystic kidney disease

c) Nephroptosis

d) Ectopic kidney

8. Which of the following arteries supplies the suprarenal gland?

a) Renal artery

b) Superior mesenteric artery

c) Median sacral artery

d) Common iliac artery

9. A 3-day-old newborn is found to have reduced renal perfusion. Which vessel’s constriction could cause this?

a) Common iliac artery

b) Umbilical artery

c) Renal artery

d) Internal pudendal artery

10. Which of the following changes occur in renal blood supply after birth?

a) Blood supply shifts from common iliac to aortic origin

b) Blood supply remains same

c) Blood supply shifts to external iliac artery

d) Blood supply decreases due to closure of umbilical arteries

11. A clinical case of ectopic kidney shows its blood supply derived from which artery?

a) Common iliac artery

b) Abdominal aorta

c) Superior mesenteric artery

d) Renal artery

Explanation:

The common iliac artery supplies the kidney in early fetal life. As the kidney ascends during development, its arterial source changes sequentially—from common iliac to abdominal aorta. Clinical remnants may persist as accessory renal arteries. Understanding these variations is crucial for renal surgery, transplantation, and diagnosing congenital anomalies.

Topic: Development of Kidneys and Their Blood Supply

Subtopic: Embryological Origin of Renal Arteries

Keyword Definitions:

• Renal Arteries: Paired arteries arising from the abdominal aorta to supply the kidneys.

• Common Iliac Artery: One of the terminal branches of the abdominal aorta dividing into internal and external iliac arteries.

• Mesonephros: The embryonic kidney that functions temporarily before the metanephros develops.

• Metanephros: The definitive kidney, developing in the pelvis and ascending during fetal life.

• Aorta: The main arterial trunk supplying oxygenated blood to the systemic circulation.

Lead Question – 2014

Initially, renal arteries are branches of?

a) Internal pudendal artery

b) External iliac artery

c) Common iliac artery

d) Aorta

Explanation: In early embryonic life, kidneys develop in the pelvic region and receive their blood supply from branches of the common iliac arteries. As kidneys ascend, their arterial supply shifts sequentially to higher levels, finally deriving from the abdominal aorta. The transient arteries regress as the kidney ascends. Hence, the correct answer is c) Common iliac artery.

1. During kidney ascent, which artery becomes the final source of its blood supply?

a) Common iliac artery

b) Abdominal aorta

c) Internal iliac artery

d) Median sacral artery

Explanation: Initially supplied by branches from the common iliac artery, the kidney ascends to the lumbar region where it ultimately receives blood from the abdominal aorta. Lower vessels regress, and the renal arteries from the aorta become the definitive arterial supply. Therefore, the correct answer is b) Abdominal aorta.

2. Accessory renal arteries arise due to:

a) Failure of regression of primitive renal arteries

b) Abnormal division of the aorta

c) Persistent mesonephric arteries

d) Recanalization defects

Explanation: Accessory renal arteries result from the persistence of embryonic renal arteries that normally regress as the kidney ascends. They may arise from the aorta or iliac arteries and are common anatomical variations. These vessels are functionally important and supply specific kidney segments. Thus, the correct answer is a) Failure of regression of primitive renal arteries.

3. The kidney ascends from the pelvis to the lumbar region during which week of development?

a) 3rd week

b) 4th–5th week

c) 6th–9th week

d) 10th–12th week

Explanation: The metanephric kidneys initially lie in the pelvic region and ascend to their lumbar position between the 6th and 9th weeks of gestation. The ascent is due to body growth and decreased curvature of the embryo. Hence, the correct answer is c) 6th–9th week.

4. A patient with a pelvic kidney has its arterial supply most likely from:

a) Abdominal aorta

b) Common iliac artery

c) Superior mesenteric artery

d) Inferior mesenteric artery

Explanation: A pelvic kidney results when the kidney fails to ascend during development. It retains its early blood supply from the common iliac artery. The renal vessels are shorter, and this anomaly is often incidental but may cause ureteral obstruction. The correct answer is b) Common iliac artery.

5. During embryonic development, which structure gives rise to the definitive kidney?

a) Pronephros

b) Mesonephros

c) Metanephros

d) Wolffian duct

Explanation: The metanephros forms the permanent kidney. It appears in the 5th week, derived from the ureteric bud (collecting system) and metanephric blastema (nephrons). The pronephros and mesonephros regress. Thus, the answer is c) Metanephros.

6. (Clinical) An aberrant renal artery crossing the ureter anteriorly may cause:

a) Hydronephrosis

b) Renal vein thrombosis

c) Pyelonephritis

d) Renal failure

Explanation: An aberrant renal artery may cross the ureter anteriorly, compressing it and obstructing urine flow, leading to hydronephrosis. This condition causes flank pain and renal pelvis dilation visible on imaging. Thus, the correct answer is a) Hydronephrosis.

7. (Clinical) A 30-year-old male with pelvic kidney presents with hematuria. Imaging shows accessory arteries from the common iliac. The cause is:

a) Ectopic kidney with persistent early blood supply

b) Renal artery stenosis

c) Inferior mesenteric artery aneurysm

d) Abnormal ureteral insertion

Explanation: A pelvic kidney receives its blood supply from the arteries at its developmental level, usually the common iliac. Persistence of embryonic vessels leads to multiple accessory arteries. Hence, the correct answer is a) Ectopic kidney with persistent early blood supply.

8. (Clinical) A patient undergoing renal transplantation has the donor renal artery anastomosed with:

a) Internal iliac artery

b) Common iliac artery

c) External iliac artery

d) Inferior epigastric artery

Explanation: In renal transplantation, the donor renal artery is usually anastomosed to the external iliac artery because of its accessibility and size match. The renal vein is connected to the external iliac vein. This provides optimal graft perfusion. Therefore, the correct answer is c) External iliac artery.

9. (Clinical) During aortic aneurysm repair, which artery must be preserved to maintain kidney perfusion?

a) Mesenteric artery

b) Renal artery

c) Lumbar artery

d) Celiac trunk

Explanation: The kidneys are supplied by the renal arteries directly from the abdominal aorta. During aneurysm repair near the renal hilum, preserving these arteries is crucial to prevent renal ischemia or infarction. Hence, the correct answer is b) Renal artery.

10. (Clinical) A 40-year-old patient with renovascular hypertension is found to have stenosis of the renal artery. The cause of hypertension is due to:

a) Increased renin release

b) Decreased angiotensin II

c) Low aldosterone

d) Increased GFR

Explanation: Renal artery stenosis reduces renal perfusion pressure, stimulating the juxtaglomerular cells to release renin. This activates the renin-angiotensin-aldosterone system, increasing blood pressure. Hence, renovascular hypertension develops. The correct answer is a) Increased renin release.

Topic: Male Urethra
Subtopic: Prostatic Urethra and Urethral Crest

Keyword Definitions:

• Urethral Crest: A longitudinal mucosal fold in the posterior wall of the prostatic urethra containing the prostatic utricle and ejaculatory ducts.

• Prostatic Urethra: The widest part of the male urethra passing through the prostate gland.

• Prostatic Glands: Compound tubuloalveolar glands secreting prostatic fluid into the urethra.

• Trigone: A smooth triangular area on the posterior wall of the urinary bladder.

Lead Question - 2014
Urethral crest is an elevation seen in urethra due to:
a) Prostatic glands
b) Insertion of detrusor muscle
c) Insertion of trigone
d) Preprostatic internal sphincter

Explanation: The urethral crest is a longitudinal mucosal ridge in the prostatic urethra formed by the median lobe of the prostate containing prostatic glands and the prostatic utricle. It helps in the closure of the urethra during ejaculation. Answer: a) Prostatic glands.

1. Which structure opens on each side of the prostatic utricle?
a) Ejaculatory ducts
b) Bulbourethral glands
c) Prostatic sinuses
d) Ducts of Cowper’s glands

The ejaculatory ducts open on each side of the prostatic utricle within the prostatic urethra. These ducts convey sperm and seminal fluid from the seminal vesicles and vas deferens. Answer: a) Ejaculatory ducts.

2. The urethral crest is located in which part of the male urethra?
a) Membranous urethra
b) Spongy urethra
c) Prostatic urethra
d) Penile urethra

The urethral crest is a prominent mucosal elevation found in the posterior wall of the prostatic urethra. It is absent in the membranous and penile urethra. Answer: c) Prostatic urethra.

3. Clinical case: A 65-year-old man with benign prostatic hyperplasia shows obstruction at the level of the urethral crest. Which lobe is responsible?
a) Median lobe
b) Anterior lobe
c) Posterior lobe
d) Lateral lobe

The median lobe of the prostate lies between the ejaculatory ducts and urethra, forming the urethral crest. Its hypertrophy causes urethral obstruction in benign prostatic hyperplasia. Answer: a) Median lobe.

4. The depression on either side of the urethral crest is called:
a) Prostatic sinus
b) Urethral groove
c) Urethral recess
d) Prostatic sac

On either side of the urethral crest are the prostatic sinuses, into which the ducts of the prostate gland open. These sinuses convey prostatic secretions into the urethra. Answer: a) Prostatic sinus.

5. The prostatic utricle is a remnant of which embryological structure?
a) Mesonephric duct
b) Paramesonephric duct
c) Urogenital sinus
d) Cloacal membrane

The prostatic utricle is a vestigial remnant of the paramesonephric (Müllerian) duct in males and opens at the summit of the urethral crest. Answer: b) Paramesonephric duct.

6. Clinical case: A male patient has infection extending from the urethra to the prostate via prostatic ducts. Which region is primarily affected?
a) Urethral crest
b) Membranous urethra
c) External sphincter
d) Ureteric orifice

Infection can spread through the ducts opening into the prostatic sinuses adjacent to the urethral crest, leading to prostatitis. Answer: a) Urethral crest.

7. Which part of the urethra passes through the deep perineal pouch?
a) Prostatic urethra
b) Membranous urethra
c) Penile urethra
d) Bulbous urethra

The membranous urethra passes through the deep perineal pouch surrounded by the external urethral sphincter. Answer: b) Membranous urethra.

8. The external urethral sphincter is innervated by:
a) Pelvic splanchnic nerves
b) Pudendal nerve
c) Inferior hypogastric plexus
d) Ilioinguinal nerve

The external urethral sphincter is supplied by the pudendal nerve (S2–S4), providing voluntary control over micturition. Answer: b) Pudendal nerve.

9. Clinical case: A 50-year-old male presents with difficulty in urination. Cystoscopy reveals hypertrophy near the urethral crest. Likely diagnosis?
a) Benign prostatic hyperplasia
b) Bladder carcinoma
c) Urethral stricture
d) Cystitis

Hypertrophy of the median lobe near the urethral crest compresses the urethra, typical of benign prostatic hyperplasia. Answer: a) Benign prostatic hyperplasia.

10. The posterior urethral wall in the prostatic part shows:
a) Colliculus seminalis
b) Fossa navicularis
c) Bulbar enlargement
d) Lacuna magna

The colliculus seminalis (verumontanum) is a raised area on the posterior urethral wall representing the urethral crest with openings of ejaculatory ducts and utricle. Answer: a) Colliculus seminalis.

Chapter: Renal Physiology; Topic: Osmotic Diuretics; Subtopic: Mannitol and Fluid Osmolarity

Keyword Definitions:

• Mannitol: An osmotic diuretic used to reduce intracranial and intraocular pressure by increasing plasma osmolarity.

• Osmolarity: The concentration of solute particles in a solution, influencing water movement across membranes.

• Intracranial Pressure (ICP): The pressure within the skull; elevated levels can impair cerebral perfusion.

• Osmotic Diuretic: A substance that promotes diuresis by increasing osmotic pressure in renal tubules, preventing water reabsorption.

Lead Question - 2014
Mannitol infusion causes increase in
a) Blood viscosity
b) Osmolarity
c) Intra-ocular tension
d) Intracranial tension

Answer & Explanation: (b) Osmolarity. Mannitol increases plasma osmolarity, drawing water out of brain and ocular tissues, thereby reducing intracranial and intraocular pressures. It is filtered by the glomerulus but not reabsorbed, causing osmotic diuresis. Excess use can lead to dehydration or hypernatremia if water loss exceeds sodium excretion.

1. Mannitol is primarily used in the management of:
a) Congestive heart failure
b) Acute renal failure (oliguric phase)
c) Intracranial hypertension
d) Hypertension
Answer & Explanation: (c) Intracranial hypertension. Mannitol reduces intracranial pressure by creating an osmotic gradient across the blood-brain barrier. Water moves from brain tissue into plasma, relieving cerebral edema. It is often administered intravenously in neurocritical care or post-head injury management for rapid pressure reduction.

2. Which of the following is a contraindication for mannitol use?
a) Glaucoma
b) Cerebral edema
c) Anuria due to renal failure
d) Raised intracranial pressure
Answer & Explanation: (c) Anuria due to renal failure. Mannitol requires filtration through the glomeruli for its action. In anuria, it accumulates in plasma, worsening fluid overload and leading to pulmonary edema or heart failure. Hence, renal function must be ensured before administration.

3. A 45-year-old male with head trauma is given mannitol. The drug’s primary mechanism is:
a) Decreasing cerebrospinal fluid production
b) Increasing plasma osmolarity
c) Vasodilation of cerebral vessels
d) Blocking aquaporins in the nephron
Answer & Explanation: (b) Increasing plasma osmolarity. Mannitol increases extracellular osmolarity, drawing water out of brain cells and lowering cerebral edema. It acts rapidly, improving cerebral perfusion pressure and oxygen delivery, which are crucial in head injury management.

4. Prolonged mannitol infusion may lead to:
a) Hyponatremia
b) Pulmonary edema
c) Hypokalemia
d) Hypercalcemia
Answer & Explanation: (b) Pulmonary edema. If mannitol draws excessive water into the vascular space without adequate excretion, plasma volume expansion occurs. This can precipitate pulmonary congestion, particularly in patients with heart failure or compromised renal function.

5. The major site of mannitol action in the nephron is:
a) Proximal tubule
b) Loop of Henle
c) Distal convoluted tubule
d) Collecting duct
Answer & Explanation: (a) Proximal tubule. Mannitol acts primarily in the proximal tubule and descending limb of the loop of Henle, where it inhibits water reabsorption by increasing tubular osmotic pressure. This results in increased urine output and excretion of electrolytes.

6. In acute glaucoma, mannitol reduces intraocular pressure by:
a) Stimulating aqueous humor secretion
b) Decreasing aqueous humor formation
c) Drawing fluid from the eye into plasma
d) Increasing choroidal blood flow
Answer & Explanation: (c) Drawing fluid from the eye into plasma. Mannitol increases plasma osmolarity, pulling water from ocular tissues via osmotic gradient. This reduces intraocular volume and pressure, providing rapid relief in acute glaucoma before surgical or definitive management.

7. In a patient with cerebral edema, excessive mannitol administration can lead to:
a) Rebound intracranial hypertension
b) Bradycardia
c) Hypoglycemia
d) Hypotension
Answer & Explanation: (a) Rebound intracranial hypertension. With prolonged or excessive dosing, mannitol crosses a damaged blood-brain barrier and draws water back into the brain, worsening edema. Monitoring osmolarity and using intermittent dosing helps prevent this complication in neurocritical settings.

8. Mannitol should be avoided in which of the following cardiac conditions?
a) Pericarditis
b) Heart failure
c) Myocarditis
d) Stable angina
Answer & Explanation: (b) Heart failure. Mannitol expands intravascular volume initially, which can overload the failing heart and precipitate pulmonary edema. Therefore, it must be avoided or used with extreme caution in patients with congestive cardiac failure or reduced ejection fraction.

9. A patient on mannitol therapy shows serum osmolarity of 340 mOsm/L. The infusion should be:
a) Increased
b) Continued
c) Reduced
d) Stopped immediately
Answer & Explanation: (d) Stopped immediately. Serum osmolarity beyond 320 mOsm/L increases risk of renal failure and CNS toxicity. Mannitol should be discontinued at this threshold to prevent osmotic nephrosis and electrolyte imbalances associated with hyperosmolarity.

10. Which electrolyte disturbance is commonly seen with mannitol use?
a) Hyperkalemia
b) Hyponatremia
c) Hypokalemia
d) Hypernatremia
Answer & Explanation: (d) Hypernatremia. Mannitol-induced osmotic diuresis leads to water loss exceeding sodium excretion, causing hypernatremia and dehydration. Monitoring serum sodium and osmolarity during therapy helps prevent neurologic complications and maintain proper fluid balance.

Topic: Urinary Bladder; Subtopic: Development of Trigone of Bladder

Keyword Definitions:

• Trigone of bladder: Smooth triangular area on the bladder’s posterior wall, bounded by ureteric orifices and the internal urethral orifice.

• Mesoderm: The middle embryonic germ layer forming muscles, bones, and urogenital structures.

• Endoderm: The innermost germ layer giving rise to the epithelial lining of the urinary bladder except trigone.

• Mesonephric duct: Embryonic duct that contributes to formation of trigone and male genital organs.

Lead Question - 2014

Trigone of urinary bladder develops from:

a) Mesoderm

b) Ectoderm

c) Endoderm of urachus

d) None of the above

Explanation: The trigone of the urinary bladder develops from the mesonephric ducts (mesodermal origin). As the ducts are absorbed into the posterior wall of the bladder, their tissue forms the trigone region. The remaining bladder, including the dome and body, arises from the endoderm of the urogenital sinus. Answer: a) Mesoderm.

1) Which part of the urinary bladder develops from endoderm?

a) Trigone

b) Body of bladder

c) Neck of bladder

d) Apex of bladder

Explanation: Except for the trigone, all other parts of the urinary bladder — the body, neck, and apex — develop from the endoderm of the urogenital sinus. This distinction explains the different epithelial origins of the trigone and rest of the bladder wall. Answer: b) Body of bladder.

2) In males, the mesonephric duct contributes to the development of?

a) Ureter

b) Seminal vesicles

c) Trigone of bladder

d) Both b and c

Explanation: The mesonephric ducts play a dual role — forming the trigone of the bladder and also giving rise to the seminal vesicles and ejaculatory ducts in males. This shared embryologic origin explains their close anatomical relationship near the bladder base. Answer: d) Both b and c.

3) A defect in mesonephric duct absorption can result in which anomaly?

a) Double ureter

b) Urachal fistula

c) Exstrophy of bladder

d) Vesicoureteral reflux

Explanation: Improper absorption of the mesonephric ducts into the posterior bladder wall can lead to vesicoureteral reflux (VUR). In this condition, urine flows back from the bladder to the ureters and kidneys, predisposing the patient to recurrent infections. Answer: d) Vesicoureteral reflux.

4) Which germ layer forms the muscular wall of the urinary bladder?

a) Mesoderm

b) Ectoderm

c) Endoderm

d) Neuroectoderm

Explanation: The muscular wall of the urinary bladder, including the detrusor muscle, originates from the mesoderm. The endoderm forms only the epithelial lining, while mesoderm contributes to the connective tissue and smooth muscle. Answer: a) Mesoderm.

5) In a newborn, an anomaly involving incomplete closure of the urachus may result in?

a) Patent urachus

b) Ureteric stenosis

c) Trigonitis

d) Hydronephrosis

Explanation: If the urachus (a fetal connection between bladder and umbilicus) fails to close, it results in a patent urachus. This causes urine leakage through the umbilicus. The urachus normally becomes the median umbilical ligament after birth. Answer: a) Patent urachus.

6) A 35-year-old male presents with reflux nephropathy. The defect likely involves?

a) Endodermal bladder lining

b) Mesonephric duct remnant

c) Trigone development

d) Urachal cyst

Explanation: Reflux nephropathy is caused by a developmental defect in the trigone and the oblique entry of the ureters into the bladder. Faulty mesonephric duct incorporation leads to poor valvular closure, allowing urine reflux. Answer: c) Trigone development.

7) Which of the following statements about bladder trigone is true?

a) Derived from urogenital sinus endoderm

b) Smooth mucosa and immovable

c) Highly distensible

d) Lies on bladder dome

Explanation: The trigone has smooth, firmly adherent mucosa that does not form folds, unlike other parts of the bladder. It is mesodermal in origin and located at the base of the bladder, forming a functional unit with the ureteric and urethral openings. Answer: b) Smooth mucosa and immovable.

8) During cystoscopy, the trigone is identified by?

a) Rough mucosa

b) Folded appearance

c) Smooth triangular area

d) Raised ridges

Explanation: On cystoscopy, the trigone appears as a smooth triangular area between the ureteric orifices and the internal urethral orifice. Its mucosa is tightly adherent to the muscle beneath, distinguishing it from the folded dome mucosa. Answer: c) Smooth triangular area.

9) A defect in which embryologic process causes duplicated ureteric orifices within the trigone?

a) Double budding of ureteric bud

b) Failure of mesonephric fusion

c) Abnormal urachus closure

d) Cloacal septation defect

Explanation: Double ureteric buds from the mesonephric duct during early development may lead to two ureters draining separately into the bladder trigone. This duplication is a congenital anomaly often seen on imaging studies. Answer: a) Double budding of ureteric bud.

10) The nerve supply to the trigone of bladder is primarily from?

a) Hypogastric plexus

b) Pelvic splanchnic nerves

c) Pudendal nerve

d) Genitofemoral nerve

Explanation: The trigone and neck of the bladder receive sympathetic innervation from the hypogastric plexus (T11–L2), which maintains sphincter control. Parasympathetic supply from pelvic splanchnic nerves mediates detrusor contraction during micturition. Answer: a) Hypogastric plexus.

11) In males, the trigone lies superior to which structure?

a) Seminal vesicles

b) Prostate gland

c) Rectum

d) Vas deferens

Explanation: The trigone forms the base of the bladder and lies directly above the prostate gland in males. This anatomical relationship explains how prostatic enlargement can cause urinary symptoms due to pressure on the bladder neck. Answer: b) Prostate gland.

Topic: Urinary Bladder

Subtopic: Trigone of Bladder

Keyword Definitions:

• Trigone of bladder: A smooth triangular area on the internal surface of the bladder base bounded by two ureteric orifices and the internal urethral orifice.

• Transitional epithelium: Specialized epithelium that lines most of the urinary tract and allows stretching.

• Mesonephric duct: Embryonic duct giving rise to male genital structures and part of the bladder trigone.

• Internal urethral orifice: Opening at the lower end of trigone leading into urethra.

Lead Question - 2014

False regarding trigone of bladder?

a) Lined by transitional epithelium

b) Mucosa smooth and firmly adherent

c) Internal urethral orifice lies at lateral angle of base

d) Developed from mesonephric duct

Explanation: The trigone of the bladder is a smooth triangular area between the ureteric and internal urethral orifices. It is lined by transitional epithelium, its mucosa is firmly adherent to the muscular layer, and it develops from the mesonephric ducts. The internal urethral orifice lies at the inferior angle, not lateral. Answer: c) Internal urethral orifice lies at lateral angle of base.

1) The apex of the urinary bladder is connected to the umbilicus by?

a) Median umbilical ligament

b) Medial umbilical ligament

c) Urachus

d) Both a and c

Explanation: The apex of the bladder is connected to the umbilicus by the median umbilical ligament, a fibrous remnant of the urachus. This structure represents the obliterated allantoic duct from fetal development and extends from the bladder’s apex to the umbilicus. Answer: a) Median umbilical ligament.

2) Which part of the urinary bladder is least distensible?

a) Apex

b) Trigone

c) Body

d) Fundus

Explanation: The trigone is the least distensible part of the bladder due to its mucosa being tightly adherent to the underlying muscle. Unlike other regions, it remains smooth even when the bladder is empty, facilitating consistent function of the ureteric and urethral openings. Answer: b) Trigone.

3) During catheterization, urine first enters which part of the bladder?

a) Apex

b) Fundus

c) Trigone

d) Neck

Explanation: During catheterization, urine enters through the neck of the bladder, which continues into the internal urethral orifice. This area corresponds to the inferior angle of the trigone and is the most dependent part of the bladder when in the upright position. Answer: d) Neck.

4) Which muscle forms the internal urethral sphincter?

a) Pubococcygeus

b) Detrusor muscle (circular fibers)

c) External sphincter muscle

d) Compressor urethrae

Explanation: The internal urethral sphincter is formed by the circular fibers of the detrusor muscle near the neck of the bladder. It plays a key role in preventing retrograde ejaculation in males by closing during ejaculation. Answer: b) Detrusor muscle (circular fibers).

5) In males, the trigone of the bladder is related posteriorly to which structure?

a) Seminal vesicles

b) Rectum

c) Prostate gland

d) Vas deferens

Explanation: The posterior surface of the male bladder, including the region near the trigone, is related to the seminal vesicles and vas deferens. These structures form the ejaculatory ducts which open into the prostatic urethra below the bladder. Answer: a) Seminal vesicles.

6) A patient presents with backflow of urine from the bladder into ureters. Which structure is defective?

a) Trigone muscle

b) Ureteric orifices

c) Vesicoureteral junction

d) Internal sphincter

Explanation: Vesicoureteral reflux occurs when the oblique intramural passage of ureters through the bladder wall is defective. Normally, contraction of the bladder compresses these tunnels to prevent reflux. A defect in this junction leads to recurrent infection. Answer: c) Vesicoureteral junction.

7) Which part of the bladder is derived from the endoderm of the urogenital sinus?

a) Trigone

b) Body of bladder

c) Ureteric orifices

d) Both a and b

Explanation: The body of the bladder develops from the endoderm of the urogenital sinus, while the trigone develops from the mesonephric ducts (mesodermal origin). This dual embryological origin explains the distinct developmental patterns of the bladder regions. Answer: b) Body of bladder.

8) In cystoscopy, the trigone appears smooth and triangular because?

a) It has thick muscle layer

b) Mucosa firmly adherent

c) Covered by non-keratinized epithelium

d) It lacks blood vessels

Explanation: The smooth appearance of the trigone in cystoscopy is due to its firmly adherent mucosa, which does not form folds like other bladder regions. This helps maintain the orientation of ureteric orifices for proper urine flow. Answer: b) Mucosa firmly adherent.

9) In a newborn male, the internal urethral sphincter fails to close during voiding. This may cause?

a) Urinary retention

b) Retrograde ejaculation

c) Bladder prolapse

d) Hydronephrosis

Explanation: Failure of closure of the internal urethral sphincter can cause retrograde ejaculation in males, where semen enters the bladder during ejaculation instead of exiting through the urethra. This occurs due to weakness of circular detrusor fibers. Answer: b) Retrograde ejaculation.

10) A patient with recurrent cystitis shows mucosal inflammation limited to the trigone. This is termed?

a) Interstitial cystitis

b) Trigonitis

c) Vesiculitis

d) Pyelonephritis

Explanation: Trigonitis is localized inflammation of the bladder trigone, commonly seen in women due to recurrent urinary tract infections. The mucosa becomes edematous and hyperemic but the rest of the bladder remains unaffected. Answer: b) Trigonitis.

11) During bladder filling, stretch receptors are most concentrated in?

a) Dome

b) Trigone

c) Apex

d) Neck

Explanation: Stretch receptors in the trigone and neck of the bladder detect bladder distension and send signals via the pelvic splanchnic nerves to initiate micturition reflex. Their high concentration helps regulate controlled urination. Answer: b) Trigone.

Topic: Ureter

Subtopic: Developmental Anomalies of Ureter

Keyword Definitions:

• Circumcaval ureter: A rare congenital anomaly where the ureter passes posterior to the inferior vena cava (IVC) and then loops anteriorly to reach the bladder.

• Inferior vena cava (IVC): The large vein that returns deoxygenated blood from the lower body to the right atrium of the heart.

• Type 1 and Type 2 circumcaval ureter: Type 1 has a “fish-hook” shape; Type 2 has a higher loop with less obstruction.

• Embryological cause: Abnormal persistence of the right posterior cardinal vein leads to a circumcaval ureter.

Lead Question (2014): True about circumcaval ureter?

a) Developmental anomaly of ureter

b) Ureter passes in front of IVC from lateral to medial

c) Mostly involves right ureter

d) Type 2 is more common

Explanation: Circumcaval ureter is a developmental anomaly of the right ureter where it passes behind the IVC before turning anteriorly. It results from abnormal persistence of the right posterior cardinal vein during development. Answer: a) Developmental anomaly of ureter

1. Which embryological structure is responsible for circumcaval ureter formation?

a) Right posterior cardinal vein

b) Left subcardinal vein

c) Right vitelline vein

d) Common iliac vein

Explanation: Circumcaval ureter occurs due to abnormal persistence of the right posterior cardinal vein, which forms part of the IVC and traps the ureter behind it. Answer: a) Right posterior cardinal vein

2. Circumcaval ureter is most commonly found on which side?

a) Left side

b) Right side

c) Bilateral

d) Midline

Explanation: The circumcaval ureter almost always involves the right ureter because of its close embryological association with the formation of the inferior vena cava on the right side. Answer: b) Right side

3. Which radiological appearance is characteristic of circumcaval ureter on intravenous pyelography?

a) Fish-hook or S-shaped loop

b) Cobra-head deformity

c) Bird-beak sign

d) String sign

Explanation: The circumcaval ureter gives a classic “fish-hook” or “S-shaped” deformity on IVP due to looping of the ureter behind and around the IVC. Answer: a) Fish-hook or S-shaped loop

4. A 35-year-old male presents with right flank pain and hydronephrosis. Imaging shows the ureter looping behind the IVC. What is the diagnosis?

a) Circumcaval ureter

b) Retroperitoneal fibrosis

c) Horseshoe kidney

d) Duplex ureter

Explanation: Right-sided hydronephrosis due to looping of the ureter behind the IVC confirms the diagnosis of circumcaval ureter. Answer: a) Circumcaval ureter

5. Which type of circumcaval ureter is more common?

a) Type 1

b) Type 2

c) Type 3

d) Both equally

Explanation: Type 1 circumcaval ureter, showing a low loop and significant obstruction, is more common than Type 2, which is high and less obstructive. Answer: a) Type 1

6. In circumcaval ureter, the ureter crosses the IVC from -

a) Posterior to anterior

b) Anterior to posterior

c) Medial to lateral

d) Superior to inferior

Explanation: The ureter passes from posterior to anterior around the IVC, creating a characteristic loop and possible obstruction. Answer: a) Posterior to anterior

7. A CT scan shows right-sided hydronephrosis with the ureter passing posterior to the IVC. Which treatment is appropriate?

a) Ureteroureterostomy anterior to IVC

b) Nephrectomy

c) Stenting only

d) Observation

Explanation: Surgical correction involves ureteroureterostomy, repositioning the ureter anterior to the IVC to relieve obstruction and restore normal flow. Answer: a) Ureteroureterostomy anterior to IVC

8. Which symptom is commonly seen in circumcaval ureter?

a) Right flank pain

b) Hematuria

c) Incontinence

d) Polyuria

Explanation: Right flank pain due to hydronephrosis and ureteral obstruction is the most common presenting symptom of circumcaval ureter. Answer: a) Right flank pain

9. Which diagnostic imaging is most accurate for confirming circumcaval ureter?

a) Contrast-enhanced CT scan

b) Ultrasound

c) Plain X-ray

d) MRI abdomen

Explanation: Contrast-enhanced CT scan clearly shows the course of the ureter passing posterior to the IVC, confirming circumcaval ureter with high accuracy. Answer: a) Contrast-enhanced CT scan

10. A patient with recurrent urinary tract infections and right flank pain is diagnosed with circumcaval ureter. What complication may arise if untreated?

a) Hydronephrosis and renal damage

b) Pyelolithiasis only

c) Bilateral renal failure

d) Bladder carcinoma

Explanation: Persistent obstruction from circumcaval ureter can cause hydronephrosis, infection, and eventual renal parenchymal damage if left untreated. Answer: a) Hydronephrosis and renal damage 

Topic: Inborn Errors of Metabolism

Subtopic: Maple Syrup Urine Disease

Keyword Definitions:

• Maple Syrup Urine Disease (MSUD): Genetic disorder due to defect in branched-chain α-keto acid dehydrogenase complex.

• Type Ia MSUD: Subtype linked to mutation in E1α subunit gene (BCKDHA).

• Gene Mutation: Permanent alteration in DNA sequence affecting protein function.

• Branched-chain Amino Acids: Leucine, isoleucine, and valine metabolized via BCKD complex.

• Inheritance: MSUD is transmitted as an autosomal recessive condition.

• Leucine Toxicity: Excess leucine causes severe neurological dysfunction in MSUD.

• Tandem Mass Spectrometry: Diagnostic tool for detecting amino acid disorders in neonates.

• Thiamine: Cofactor of E1 activity in the BCKD complex.

• Burnt Sugar Odor: Characteristic maple syrup-like smell in urine of MSUD patients.

• Dialysis: Rapid detoxification method for metabolic crisis in MSUD.

Lead Question - 2013

In type Ia maple syrup urine disease, gene mutation seen is ?

a) E1α

b) E1β

c) E2

d) E3

Explanation: Type Ia MSUD results from mutation in the E1α subunit of branched-chain α-keto acid dehydrogenase, encoded by the BCKDHA gene.

This defect blocks oxidative decarboxylation of branched-chain amino acids, leading to accumulation and toxicity.

Therefore, the correct answer is a) E1α.

1) The enzyme complex defective in maple syrup urine disease is ?

a) Pyruvate dehydrogenase

b) Branched-chain α-keto acid dehydrogenase

c) Alpha-ketoglutarate dehydrogenase

d) Glucose-6-phosphatase

Explanation: MSUD occurs due to defective branched-chain α-keto acid dehydrogenase.

This enzyme normally metabolizes leucine, isoleucine, and valine.

When absent or deficient, these amino acids and their keto acids accumulate, producing neurotoxicity.

Clinical features include seizures and developmental delay.

Correct answer is b) Branched-chain α-keto acid dehydrogenase.

2) A 10-day-old neonate presents with vomiting, poor feeding, seizures, and urine with burnt sugar odor. Most likely diagnosis is ?

a) Phenylketonuria

b) Maple syrup urine disease

c) Alkaptonuria

d) Tyrosinemia

Explanation: A neonate with encephalopathy, seizures, poor feeding, and urine with burnt sugar odor is strongly suggestive of MSUD.

The disease presents in early life and may be fatal without rapid treatment.

Early diagnosis improves outcomes significantly.

Correct answer is b) Maple syrup urine disease.

3) Which branched-chain amino acid is most neurotoxic in maple syrup urine disease?

a) Leucine

b) Valine

c) Isoleucine

d) All equally toxic

Explanation: Although all branched-chain amino acids accumulate in MSUD, leucine is the most neurotoxic.

Elevated leucine levels cause cerebral edema, seizures, and brain damage.

Clinical management often focuses on rapid reduction of leucine concentration.

Therefore, the correct answer is a) Leucine.

4) A 6-month-old child with developmental delay is suspected of MSUD. Which confirmatory test is most appropriate?

a) Benedict’s test

b) Tandem mass spectrometry

c) Rothera’s test

d) Seliwanoff’s test

Explanation: Tandem mass spectrometry detects elevated plasma leucine, isoleucine, and valine levels, confirming MSUD.

It is also used in neonatal screening programs, ensuring early diagnosis and timely treatment.

This makes it the investigation of choice for suspected cases.

Correct answer is b) Tandem mass spectrometry.

5) Inheritance pattern of maple syrup urine disease is ?

a) Autosomal dominant

b) Autosomal recessive

c) X-linked dominant

d) Mitochondrial

Explanation: MSUD follows autosomal recessive inheritance, requiring mutations in both alleles for disease manifestation.

Parents are usually carriers without clinical features.

Risk of disease recurrence in siblings is 25% for carrier couples.

Correct answer is b) Autosomal recessive.

6) A neonate with MSUD develops acute encephalopathy. Immediate management includes ?

a) Vitamin C supplementation

b) Dialysis and intravenous glucose

c) High protein diet

d) Iron therapy

Explanation: Acute metabolic crises in MSUD are treated with dialysis to remove toxic metabolites and IV glucose to suppress catabolism.

This rapidly lowers amino acid levels and prevents further neurological injury.

Correct answer is b) Dialysis and intravenous glucose.

7) Which cofactor is essential for branched-chain α-keto acid dehydrogenase activity?

a) Thiamine pyrophosphate

b) Biotin

c) Vitamin C

d) Folic acid

Explanation: Branched-chain α-keto acid dehydrogenase requires several cofactors for function, including thiamine pyrophosphate, FAD, NAD+, and lipoic acid.

Thiamine is essential for E1 enzyme activity, and supplementation may benefit thiamine-responsive MSUD patients.

Correct answer is a) Thiamine pyrophosphate.

8) A 2-year-old child with intermittent ataxia and urine odor is diagnosed with intermittent MSUD. Which therapy may be beneficial?

a) Riboflavin

b) Thiamine

c) Pyridoxine

d) Vitamin K

Explanation: Intermittent MSUD cases may respond to high-dose thiamine supplementation, improving enzyme activity and reducing clinical episodes.

This response defines thiamine-responsive MSUD.

Correct answer is b) Thiamine.

9) A newborn screening program detects elevated leucine, isoleucine, and valine. Which disease should be suspected?

a) Alkaptonuria

b) Phenylketonuria

c) Maple syrup urine disease

d) Homocystinuria

Explanation: Detection of elevated branched-chain amino acids in newborn screening strongly suggests maple syrup urine disease.

Early detection allows initiation of dietary restriction, preventing irreversible neurological damage.

Correct answer is c) Maple syrup urine disease.

10) Dietary management of MSUD primarily involves restriction of ?

a) Methionine

b) Phenylalanine

c) Leucine, isoleucine, valine

d) Tyrosine

Explanation: The cornerstone of MSUD therapy is dietary restriction of branched-chain amino acids (leucine, isoleucine, valine).

Controlled supplementation ensures normal growth while avoiding toxic accumulation.

Careful monitoring is essential to maintain metabolic balance.

Correct answer is c) Leucine, isoleucine, valine.

Topic: Fluid and Electrolyte Balance

Subtopic: Sweat and Daily Water Loss

Keyword Definitions:

• Water loss: Fluid eliminated from the body through sweat, urine, respiration, and feces.

• Sweat: Fluid secreted by sweat glands for thermoregulation.

• Normal activities: Routine daily tasks without heavy physical exertion.

• Thermoregulation: The body's process of maintaining internal temperature.

• Fluid balance: Equilibrium between water intake and water loss.

Lead Question - 2013

Daily water loss in sweat during normal activities ?

a) 50 - 100 ml

b) 200 - 400 ml

c) 500 - 700 ml

d) 1000 - 1200 ml

Explanation: During normal daily activities, sweat contributes to approximately 200–400 ml of water loss in adults, helping maintain thermoregulation. Excessive activity or heat can increase this. Other routes like urine and respiration also contribute. Answer: b) 200 - 400 ml.

1) Guess Question:

Which gland is primarily responsible for sweat secretion?

a) Sebaceous gland

b) Eccrine sweat gland

c) Apocrine sweat gland

d) Salivary gland

Explanation: Eccrine sweat glands are widely distributed and secrete watery sweat for thermoregulation. Apocrine glands contribute minimally in normal daily water loss. Sebaceous and salivary glands are not involved in sweat-mediated water loss. Answer: b) Eccrine sweat gland.

2) Guess Question:

What is the main purpose of sweating?

a) Excrete toxins

b) Thermoregulation

c) Lubrication

d) Immunity

Explanation: Sweating primarily helps maintain body temperature by dissipating heat through evaporation. While minor toxin excretion occurs, the main physiological purpose is thermoregulation. Answer: b) Thermoregulation.

3) Guess Question:

Which electrolyte is most abundant in sweat?

a) Potassium

b) Sodium

c) Calcium

d) Magnesium

Explanation: Sodium is the most abundant electrolyte in sweat, followed by chloride and potassium. This helps in water retention and electrolyte balance. Answer: b) Sodium.

4) Guess Question:

A 30-year-old worker in hot conditions loses 1 liter of sweat per hour. Likely symptom is:

a) Dehydration

b) Hypervolemia

c) Bradycardia

d) Hypernatremia

Explanation: Excessive sweating leads to significant water loss, causing dehydration, decreased plasma volume, and possible hypotension. Electrolytes may also be lost. Answer: a) Dehydration.

5) Guess Question:

Which factor increases daily sweat loss?

a) High ambient temperature

b) Fever

c) Exercise

d) All of the above

Explanation: All these factors increase sweat production to maintain body temperature. Normal daily activity contributes moderately, while fever, heat, and exercise significantly increase water loss. Answer: d) All of the above.

6) Guess Question:

During normal activities, respiratory water loss is approximately:

a) 100-200 ml

b) 400-600 ml

c) 700-900 ml

d) 1000-1200 ml

Explanation: Respiration contributes roughly 400–600 ml of daily water loss in adults at rest. Combined with sweat and urine, this maintains total fluid balance. Answer: b) 400-600 ml.

7) Guess Question:

Which hormone reduces sweat rate by increasing water retention?

a) Aldosterone

b) Cortisol

c) ADH

d) Epinephrine

Explanation: Aldosterone promotes sodium and water reabsorption in kidneys, indirectly conserving fluid and reducing excessive sweat loss. ADH also conserves water but acts mainly on kidneys. Answer: a) Aldosterone.

8) Guess Question:

A patient with hypohidrosis will likely show:

a) Excessive sweating

b) Reduced sweat and heat intolerance

c) Hypernatremia

d) Polyuria

Explanation: Hypohidrosis is reduced sweating, leading to impaired thermoregulation and heat intolerance. Other symptoms may include fatigue and hyperthermia during exertion. Answer: b) Reduced sweat and heat intolerance.

9) Guess Question:

Which nervous system controls sweat secretion?

a) Sympathetic

b) Parasympathetic

c) Somatic

d) Central only

Explanation: Sympathetic nervous system stimulates eccrine sweat glands via cholinergic fibers for thermoregulation. Parasympathetic fibers do not control sweat. Answer: a) Sympathetic.

10) Guess Question:

Daily water loss through feces is approximately:

a) 50-100 ml

b) 200-400 ml

c) 500-700 ml

d) 800-1000 ml

Explanation: Normal fecal water loss is small, about 50–100 ml per day in healthy adults. Most daily water loss occurs via urine, sweat, and respiration. Answer: a) 50-100 ml.

Topic: Transport Mechanisms in Kidney

Subtopic: Na+-K+-Cl- Cotransporter

Keyword Definitions:

• Na+-K+-Cl- cotransporter: Membrane protein that reabsorbs sodium, potassium, and chloride ions in renal tubules.

• Transmembrane domain: Hydrophobic region of protein that spans lipid bilayer.

• Loop of Henle: Nephron segment important for countercurrent mechanism.

• Thiazide diuretics: Drugs acting on sodium-chloride cotransporter.

• Loop diuretics: Drugs inhibiting Na+-K+-Cl- cotransporter in thick ascending limb.

Lead Question (2013):
Na+-K+-Cl- cotransporter contains?
a) 5 transmembrane spanning domain
b) 7 transmembrane spanning domain
c) 9 transmembrane spanning domain
d) 12 transmembrane spanning domain

Explanation: The Na+-K+-Cl- cotransporter is an integral membrane protein with 12 transmembrane spanning domains. It plays a crucial role in salt reabsorption, particularly in the thick ascending limb of the loop of Henle. Loop diuretics inhibit this transporter. Answer: d) 12 transmembrane spanning domain.

1) Guess Question:
Which nephron segment expresses the Na+-K+-Cl- cotransporter predominantly?
a) Proximal tubule
b) Thick ascending limb of loop of Henle
c) Distal tubule
d) Collecting duct

Explanation: The Na+-K+-Cl- cotransporter is localized mainly in the thick ascending limb of the loop of Henle. This segment reabsorbs significant sodium, potassium, and chloride ions, crucial for urine concentration. Answer: b) Thick ascending limb of loop of Henle.

2) Guess Question:
A patient with edema is prescribed furosemide. Its target site is:
a) Na+-Cl- cotransporter
b) Na+-K+-Cl- cotransporter
c) Na+-glucose cotransporter
d) Na+-H+ exchanger

Explanation: Furosemide, a loop diuretic, specifically inhibits the Na+-K+-Cl- cotransporter in the thick ascending limb of the loop of Henle, enhancing diuresis. Other transporters are not affected. Answer: b) Na+-K+-Cl- cotransporter.

3) Guess Question:
Which ion movement drives the Na+-K+-Cl- cotransporter?
a) Passive chloride gradient
b) Sodium electrochemical gradient
c) Active potassium pumping
d) Water reabsorption

Explanation: The Na+-K+-Cl- cotransporter relies on the sodium electrochemical gradient, maintained by Na+/K+ ATPase, to drive cotransport of potassium and chloride. Passive chloride movement and water reabsorption are secondary. Answer: b) Sodium electrochemical gradient.

4) Guess Question:
A 50-year-old hypertensive patient on loop diuretics develops hypokalemia. The mechanism is:
a) Enhanced distal sodium delivery leading to potassium loss
b) Direct potassium secretion in proximal tubule
c) Decreased renin release
d) Reduced aldosterone sensitivity

Explanation: Loop diuretics inhibit Na+-K+-Cl- cotransporter, increasing sodium delivery to distal nephron, enhancing potassium secretion, leading to hypokalemia. Direct proximal secretion and reduced renin/aldosterone sensitivity are not primary mechanisms. Answer: a) Enhanced distal sodium delivery leading to potassium loss.

5) Guess Question:
Which diuretic acts on Na+-Cl- cotransporter in the distal tubule?
a) Thiazides
b) Loop diuretics
c) Carbonic anhydrase inhibitors
d) Potassium-sparing diuretics

Explanation: Thiazide diuretics inhibit the Na+-Cl- cotransporter in the distal convoluted tubule, enhancing sodium and water excretion. Loop diuretics inhibit Na+-K+-Cl-, while carbonic anhydrase inhibitors and potassium-sparing diuretics act elsewhere. Answer: a) Thiazides.

6) Guess Question:
A child presents with polyuria, polydipsia, and hypokalemia. Genetic mutation in which transporter is likely?
a) Na+-Cl- cotransporter
b) Na+-K+-Cl- cotransporter
c) Aquaporin-2 channels
d) Na+-glucose cotransporter

Explanation: Mutations in the Na+-K+-Cl- cotransporter cause Bartter syndrome, leading to polyuria, polydipsia, and hypokalemia due to defective reabsorption in the thick ascending limb. Answer: b) Na+-K+-Cl- cotransporter.

7) Guess Question:
Inhibition of Na+-K+-Cl- cotransporter results in:
a) Dilution of urine
b) Concentrated urine
c) Reduced sodium excretion
d) Increased blood pressure

Explanation: Inhibition of Na+-K+-Cl- cotransporter prevents solute reabsorption in the thick ascending limb, impairing countercurrent multiplication, resulting in dilute urine and natriuresis. Answer: a) Dilution of urine.

8) Guess Question:
A 40-year-old man develops hearing loss while on high-dose loop diuretics. The cause is:
a) Ototoxicity from Na+-K+-Cl- cotransporter inhibition
b) Middle ear infection
c) Damage to auditory ossicles
d) Hypothyroidism

Explanation: Loop diuretics can cause ototoxicity by inhibiting Na+-K+-Cl- cotransporters in the stria vascularis of the inner ear, leading to sensorineural hearing loss. Answer: a) Ototoxicity from Na+-K+-Cl- cotransporter inhibition.

9) Guess Question:
Which electrolyte imbalance is commonly associated with loop diuretic therapy?
a) Hyperkalemia
b) Hypokalemia
c) Hypernatremia
d) Hypercalcemia

Explanation: Loop diuretics cause increased sodium delivery to distal nephron, leading to increased potassium excretion, resulting in hypokalemia. They also promote calcium loss, not hypercalcemia. Answer: b) Hypokalemia.

10) Guess Question:
Na+-K+-Cl- cotransporter is encoded by which gene family?
a) SLC12A family
b) SLC5A family
c) SLC9A family
d) SLC22A family

Explanation: The Na+-K+-Cl- cotransporter belongs to the solute carrier family 12 (SLC12A), which encodes cation-chloride cotransporters. SLC5A encodes sodium-glucose, SLC9A encodes sodium-hydrogen exchangers, and SLC22A encodes organic ion transporters. Answer: a) SLC12A family.

Topic: Renal Physiology
Subtopic: Body Fluid Compartments and Osmolality

Keyword Definitions:
• Serum osmolality: Measure of solute concentration in plasma, expressed as mOsm/kg of water.
• Sodium: Main extracellular ion contributing to serum osmolality.
• ADH (Vasopressin): Hormone regulating water reabsorption to maintain osmolality.
• Hyponatremia: Decreased sodium concentration causing low serum osmolality.
• Hypernatremia: Increased sodium concentration causing elevated serum osmolality.

Lead Question - 2013
Normal range of serum osmolality is (mOsm/Kg)?
a) 280 - 300
b) 250 - 270
c) 300 - 320
d) 210 - 230

Explanation:
Serum osmolality normally ranges between 280–300 mOsm/kg, primarily maintained by sodium and water balance. Deviation from this range indicates fluid-electrolyte imbalance, as seen in hyponatremia or hypernatremia. Regulation involves thirst and ADH secretion. Answer: a) 280 - 300.

1) Main determinant of serum osmolality?
a) Glucose
b) Sodium
c) Urea
d) Potassium
Explanation:
Sodium is the major extracellular cation, accounting for most of serum osmolality. Glucose and urea contribute minimally under normal conditions. Answer: b) Sodium.

2) Clinical: A patient with sodium 120 mEq/L is likely to have serum osmolality?
a) Below 280
b) 280-300
c) Above 320
d) Normal
Explanation:
Severe hyponatremia lowers serum osmolality significantly below the normal range, often causing neurological symptoms like confusion or seizures. Answer: a) Below 280.

3) Which hormone plays a central role in regulating serum osmolality?
a) Aldosterone
b) Vasopressin (ADH)
c) Insulin
d) Cortisol
Explanation:
ADH regulates water reabsorption in renal collecting ducts, adjusting plasma osmolality by concentrating or diluting urine as required. Answer: b) Vasopressin (ADH).

4) Clinical: A diabetic patient in hyperglycemia shows serum osmolality 330 mOsm/kg. What is this condition?
a) Hyponatremia
b) Hypo-osmolality
c) Hyperosmolality
d) Normal
Explanation:
Excess glucose acts as an effective osmole, elevating serum osmolality above 300, leading to hyperosmolar states. Answer: c) Hyperosmolality.

5) Osmoreceptors regulating ADH secretion are located in:
a) Medulla oblongata
b) Hypothalamus
c) Pituitary gland
d) Cerebellum
Explanation:
Osmoreceptors in the hypothalamus detect plasma osmolality changes and stimulate posterior pituitary to release ADH, maintaining balance. Answer: b) Hypothalamus.

6) Clinical: A patient with SIADH will have?
a) Increased serum osmolality
b) Decreased serum osmolality
c) Normal osmolality
d) No change
Explanation:
SIADH causes excess ADH release, leading to water retention, dilutional hyponatremia, and decreased serum osmolality. Answer: b) Decreased serum osmolality.

7) Which of the following contributes minimally to effective osmolality?
a) Sodium
b) Glucose
c) Urea
d) Potassium
Explanation:
Urea equilibrates across membranes and contributes little to effective osmolality, unlike sodium and glucose, which influence water movement. Answer: c) Urea.

8) Clinical: In dehydration, serum osmolality will be?
a) Low
b) High
c) Normal
d) Zero
Explanation:
Loss of water without proportional solute loss increases serum osmolality above normal range, stimulating thirst and ADH release. Answer: b) High.

9) Formula to calculate serum osmolality?
a) 2(Na) + Glucose/18 + BUN/2.8
b) Na + K + Cl
c) 2(K) + Creatinine
d) Na + Glucose + Protein
Explanation:
Serum osmolality is calculated as: 2 × [Na] + [Glucose]/18 + [BUN]/2.8. This approximates measured osmolality. Answer: a) 2(Na) + Glucose/18 + BUN/2.8.

10) Clinical: In mannitol therapy for cerebral edema, serum osmolality is?
a) Increased
b) Decreased
c) Normal
d) Unchanged
Explanation:
Mannitol is an osmotic agent that increases serum osmolality, drawing water out of brain cells to reduce intracranial pressure. Answer: a) Increased.

Subtopic: Carbonic Anhydrase Enzyme 

Keyword Definitions

• Carbonic Anhydrase – enzyme catalyzing conversion of CO₂ and H₂O to H₂CO₃.

• RBC – Red Blood Cells, transport oxygen and carbon dioxide.

• Plasma – liquid part of blood without cells.

• Kidney – organ filtering blood and maintaining acid-base balance.

• Brain – organ controlling body functions and maintaining pH balance.

Lead Question (2013)

Carbonic anhydrase activity found in all except?

a) Brain

b) Kidney

c) RBC

d) Plasma

Explanation: Carbonic anhydrase is present in kidney tubular cells, RBCs, and brain tissues where it helps in acid-base regulation. Plasma lacks carbonic anhydrase activity. Therefore, the correct answer is Plasma. This absence helps maintain compartmental differences in CO₂ buffering and bicarbonate regulation within the body fluids.

1) Guessed Question

Which type of carbonic anhydrase is abundant in RBCs?

a) CA I

b) CA II

c) CA III

d) CA IV

Explanation: RBCs predominantly contain Carbonic Anhydrase II, a cytoplasmic isoenzyme that rapidly catalyzes the hydration of carbon dioxide. This process is essential for CO₂ transport and bicarbonate buffer system. Hence, the correct answer is CA II, which is the most active isoenzyme in red blood cells.

2) Guessed Question

A patient with renal tubular acidosis has a defect in which enzyme?

a) Na⁺/K⁺ ATPase

b) Carbonic Anhydrase

c) Renin

d) Aldolase

Explanation: Renal tubular acidosis type II is due to defective carbonic anhydrase in the proximal tubules. This enzyme normally facilitates bicarbonate reabsorption. Without it, bicarbonate is wasted in urine, leading to acidosis. Thus, the correct answer is Carbonic Anhydrase, showing its crucial role in kidney function.

3) Guessed Question

Which drug is a carbonic anhydrase inhibitor?

a) Furosemide

b) Acetazolamide

c) Spironolactone

d) Hydrochlorothiazide

Explanation: Acetazolamide is a diuretic that inhibits carbonic anhydrase, reducing bicarbonate reabsorption in proximal tubules, causing alkaline urine and metabolic acidosis. It is used in glaucoma, altitude sickness, and some seizure disorders. Hence, the correct answer is Acetazolamide, the prototype carbonic anhydrase inhibitor drug.

4) Guessed Question

Which of the following conditions benefits from carbonic anhydrase inhibitors?

a) Glaucoma

b) Hypothyroidism

c) Hypertension only

d) Parkinson’s disease

Explanation: Carbonic anhydrase inhibitors decrease aqueous humor secretion in the eye, lowering intraocular pressure. Therefore, they are widely used in the treatment of glaucoma. While they may have other clinical uses, the main therapeutic indication remains glaucoma. Thus, the correct answer is Glaucoma, showing their ophthalmic importance.

5) Guessed Question

A mountaineer develops acute mountain sickness. Which drug helps?

a) Mannitol

b) Acetazolamide

c) Furosemide

d) Amiloride

Explanation: At high altitude, hypoxia leads to respiratory alkalosis. Acetazolamide, a carbonic anhydrase inhibitor, induces metabolic acidosis by bicarbonate excretion, which stimulates ventilation and relieves symptoms. Therefore, the correct answer is Acetazolamide. This drug is commonly used prophylactically for altitude sickness prevention in climbers.

6) Guessed Question

Carbonic anhydrase in gastric parietal cells helps in secretion of:

a) HCl

b) HCO₃⁻

c) Pepsin

d) Mucus

Explanation: In gastric parietal cells, carbonic anhydrase generates H⁺ and HCO₃⁻ from CO₂ and H₂O. The H⁺ is secreted into the stomach lumen to form hydrochloric acid (HCl). Thus, the correct answer is HCl. This mechanism is central to acid secretion in the stomach’s digestive process.

7) Guessed Question

Patient with seizures and glaucoma is prescribed a drug inhibiting carbonic anhydrase. Likely drug is:

a) Phenytoin

b) Valproate

c) Acetazolamide

d) Carbamazepine

Explanation: Acetazolamide, by inhibiting carbonic anhydrase, reduces intraocular pressure in glaucoma and also has anticonvulsant activity in absence seizures. Hence, in a patient with both glaucoma and seizures, acetazolamide is the drug of choice. Therefore, the correct answer is Acetazolamide, highlighting its dual clinical usefulness.

8) Guessed Question

Which statement about carbonic anhydrase is true?

a) Found only in plasma

b) Inhibitors cause metabolic alkalosis

c) Essential for acid-base balance

d) Not present in kidneys

Explanation: Carbonic anhydrase catalyzes CO₂ hydration, playing a vital role in maintaining acid-base homeostasis. It is widely present in RBCs, kidneys, and other tissues. Plasma lacks it. Inhibitors cause metabolic acidosis, not alkalosis. Therefore, the correct answer is “Essential for acid-base balance,” showing its systemic importance.

9) Guessed Question

In the proximal tubule, carbonic anhydrase inhibition leads to:

a) Increased HCO₃⁻ excretion

b) Increased Na⁺ reabsorption

c) Increased H⁺ secretion

d) Increased water reabsorption

Explanation: Inhibition of carbonic anhydrase reduces bicarbonate reabsorption in proximal tubule, leading to increased urinary excretion of bicarbonate. This results in alkaline urine and mild metabolic acidosis. Thus, the correct answer is Increased HCO₃⁻ excretion. This mechanism underlies the diuretic action of carbonic anhydrase inhibitors.

10) Guessed Question

Which isoform of carbonic anhydrase is membrane-bound and found in kidneys?

a) CA I

b) CA II

c) CA IV

d) CA IX

Explanation: Carbonic Anhydrase IV is a membrane-bound isoform located in the proximal tubular brush border of kidneys. It facilitates extracellular conversion of bicarbonate, essential for reabsorption processes. Therefore, the correct answer is CA IV. This demonstrates the tissue-specific isoform distribution of the enzyme in human physiology.

Topic: Renal Physiology

Subtopic: Hyperosmolarity of Renal Medulla

Keyword Definitions:

- Hyperosmolarity: Increased solute concentration in a solution compared to another solution.

- Renal Medulla: Inner region of the kidney responsible for concentration of urine.

- Sodium (Na): Electrolyte crucial for maintaining fluid balance and generating osmotic gradient.

- Osmotic Gradient: Difference in solute concentration that drives water reabsorption in kidneys.

- Countercurrent Mechanism: Physiological process in nephron contributing to medullary hyperosmolarity.

Lead Question - 2013

Hyperosmolarity of renal medulla is due to?

a) K

b) Na

c) Glucose

d) Cl

Answer and Explanation:

Correct answer is b) Na. The hyperosmolarity of the renal medulla is primarily due to sodium and chloride ions accumulating in the interstitial space via active transport in the thick ascending limb of the loop of Henle. This gradient enables water reabsorption from the collecting duct, concentrating the urine effectively.

Guessed Questions for NEET PG:

1. Main site of sodium reabsorption in nephron is?

a) Collecting duct

b) Proximal tubule

c) Loop of Henle

d) Distal tubule

Explanation: Correct answer is b) Proximal tubule. About 65% of filtered sodium is reabsorbed in the proximal tubule through various sodium transporters.

2. Countercurrent multiplication occurs in?

a) Proximal tubule

b) Loop of Henle

c) Distal tubule

d) Collecting duct

Explanation: Correct answer is b) Loop of Henle. Countercurrent multiplication in the loop of Henle generates a high osmotic gradient important for urine concentration.

3. Urea contributes to medullary hyperosmolarity by?

a) Active transport

b) Passive diffusion

c) Active secretion

d) No role

Explanation: Correct answer is b) Passive diffusion. Urea passively diffuses from the collecting duct into the medullary interstitium, contributing to hyperosmolarity.

4. Thick ascending limb of Henle is impermeable to?

a) Water

b) Sodium

c) Chloride

d) Urea

Explanation: Correct answer is a) Water. The thick ascending limb actively transports Na and Cl but is impermeable to water, aiding in osmolarity generation.

5. ADH acts on which part of nephron?

a) Proximal tubule

b) Distal tubule

c) Collecting duct

d) Loop of Henle

Explanation: Correct answer is c) Collecting duct. ADH increases water permeability in the collecting duct, enhancing water reabsorption and concentrating urine.

6. Medullary osmolarity in mOsm/kg is approximately?

a) 100

b) 300

c) 1200

d) 600

Explanation: Correct answer is c) 1200. The inner medulla achieves a high osmolarity (~1200 mOsm/kg) necessary for water reabsorption and urine concentration.

7. The primary pump generating medullary gradient is?

a) Na+/K+ ATPase

b) K+/Cl- cotransporter

c) Glucose transporter

d) Aquaporin

Explanation: Correct answer is a) Na+/K+ ATPase. Active sodium transport out of tubular cells into interstitium drives osmotic gradient generation.

8. Clinical consequence of impaired medullary osmolarity?

a) Polyuria

b) Oliguria

c) Anuria

d) Hematuria

Explanation: Correct answer is a) Polyuria. Inability to concentrate urine due to loss of medullary gradient results in excessive urine production.

9. Hyperosmolarity is essential for?

a) Glomerular filtration

b) Tubular secretion

c) Urine concentration

d) Filtration pressure

Explanation: Correct answer is c) Urine concentration. The osmotic gradient enables water reabsorption, concentrating urine according to body needs.

10. Thick ascending limb reabsorbs Na+ by?

a) Passive diffusion

b) Na-K-2Cl symporter

c) Sodium-amino acid cotransporter

d) Sodium-glucose cotransporter

Explanation: Correct answer is b) Na-K-2Cl symporter. This symporter reabsorbs sodium along with potassium and chloride, playing a key role in medullary osmolarity.

Subtopic: Renal Threshold for Glucose

Keyword Definitions:

- Renal Threshold: Plasma concentration level at which a substance begins to appear in urine.

- Glucose: A simple sugar essential for energy production in cells.

- Proximal Tubule: Part of nephron where glucose reabsorption occurs.

- Glycosuria: Presence of glucose in urine, indicating threshold exceeded.

- Plasma Glucose Level: Concentration of glucose in blood plasma measured in mg/dL.

Lead Question - 2013

Normal renal threshold for glucose is at plasma glucose level ?

a) 100 mg/dl

b) 200 mg/dl

c) 300 mg/dl

d) 400 mg/dl

Answer and Explanation:

Correct answer is b) 200 mg/dl. Normally, glucose is completely reabsorbed by the proximal tubule until the plasma glucose level exceeds approximately 180-200 mg/dl. Beyond this threshold, the transport maximum (Tm) is surpassed, resulting in glucose appearing in urine, a condition termed glycosuria.

Guessed Questions for NEET PG:

1. Glycosuria is commonly seen in:

a) Diabetes mellitus

b) Hypertension

c) Anemia

d) Hypothyroidism

Explanation: Correct answer is a) Diabetes mellitus. High plasma glucose levels exceed renal threshold, causing glucose to spill into urine (glycosuria), a key diabetes symptom.

2. The main site of glucose reabsorption in nephron is:

a) Distal tubule

b) Collecting duct

c) Proximal tubule

d) Loop of Henle

Explanation: Correct answer is c) Proximal tubule. Most glucose reabsorption occurs in the proximal tubule via sodium-glucose cotransporters.

3. Transport maximum (Tm) refers to: