Excretory Products & Their Elimination – MCQs

Part 1 — Q1–Q25

Q1. The primary nitrogenous excretory product in humans is:

a) Ammonia
b) Urea
c) Uric acid
d) Creatinine
Answer: b) Urea
Explanation: Humans are ureotelic — liver converts NH₃ to urea (less toxic). Ammonia (a) is excreted by aquatic animals; uric acid (c) is for birds/reptiles; creatinine (d) is a metabolic waste but not primary N-excretion product.

Q2. Filtration of blood in the kidney occurs in the:

a) Loop of Henle
b) Proximal convoluted tubule
c) Glomerulus (Bowman’s capsule)
d) Collecting duct
Answer: c) Glomerulus (Bowman’s capsule)
Explanation: Ultrafiltration across glomerular capillaries into Bowman’s space forms primary filtrate. PCT, loop, CD modify filtrate.

Q3. Which cells form the filtration slits around glomerular capillaries?

a) Mesangial cells
b) Podocytes (visceral epithelial cells)
c) Endothelial cells only
d) Juxtaglomerular cells
Answer: b) Podocytes
Explanation: Podocyte foot processes create slit diaphragms. Mesangial cells support and phagocytose; JG cells release renin.

Q4. Glomerular filtration rate (GFR) is most closely approximated clinically by:

a) Plasma albumin concentration
b) Creatinine clearance
c) Uric acid excretion
d) Urine osmolality
Answer: b) Creatinine clearance
Explanation: Creatinine clearance approximates GFR since creatinine is freely filtered and minimally secreted. Albumin affects oncotic pressure, not direct GFR measure.

Q5. The majority of filtered glucose is reabsorbed in the:

a) Proximal convoluted tubule (PCT)
b) Loop of Henle
c) Distal convoluted tubule (DCT)
d) Collecting duct
Answer: a) PCT
Explanation: PCT reabsorbs ~100% of filtered glucose via SGLT + GLUT transporters (until renal threshold).

Q6. Diabetes mellitus causes glucosuria primarily because:

a) Increased insulin
b) Renal failure
c) Filtered load exceeds tubular reabsorptive capacity (renal threshold)
d) Increased ADH
Answer: c) Filtered load exceeds tubular reabsorptive capacity
Explanation: High plasma glucose surpasses SGLT capacity → glucose appears in urine.

Q7. Countercurrent multiplier mechanism occurs in:

a) Proximal tubule
b) Loop of Henle (nephron loop)
c) Collecting duct only
d) Bowman’s capsule
Answer: b) Loop of Henle
Explanation: Opposing flow in descending/ascending limbs and active NaCl transport in ascending limb establish medullary gradient.

Q8. The descending limb of Henle is permeable mainly to:

a) Na⁺ and Cl⁻ actively
b) Water (highly) and relatively impermeable to solutes
c) Urea only
d) Glucose
Answer: b) Water (highly)
Explanation: Descending limb permits water exit (osmosis) into hyperosmotic medulla; ascending limb pumps out salt and is water-impermeable.

Q9. ADH (vasopressin) acts primarily by:

a) Increasing Na⁺ reabsorption in proximal tubule
b) Inserting aquaporin-2 channels in collecting duct to increase water reabsorption
c) Inhibiting aldosterone release
d) Dilating afferent arteriole
Answer: b) Inserting aquaporin-2 channels
Explanation: ADH → V2 receptor → AQP2 insertion → water permeability↑ in late DCT/CD → concentrated urine.

Q10. Aldosterone directly increases:

a) K⁺ secretion and Na⁺ reabsorption in DCT and collecting duct
b) Glucose reabsorption in PCT
c) GFR by dilating efferent arteriole
d) Water loss in urine
Answer: a) K⁺ secretion and Na⁺ reabsorption
Explanation: Aldosterone upregulates ENaC and Na⁺/K⁺-ATPase → Na⁺ retention and K⁺ excretion.

Q11. Which hormone is secreted by juxtaglomerular cells?

a) ADH
b) Renin
c) Aldosterone
d) ANP
Answer: b) Renin
Explanation: JG cells (afferent arteriole) release renin in response to low BP, sympathetic stimulation, or low NaCl at macula densa.

Q12. Angiotensin II causes:

a) Systemic vasodilation
b) Systemic vasoconstriction + increased aldosterone → ↑BP
c) Decreased thirst
d) ADH inhibition
Answer: b) Systemic vasoconstriction + increased aldosterone
Explanation: Ang II raises BP via vasoconstriction and stimulates aldosterone release and ADH/thirst.

Q13. Renal clearance of a substance equals zero when:

a) Substance is freely filtered and neither reabsorbed nor secreted
b) Substance is completely reabsorbed (no excretion)
c) Substance is secreted into tubule
d) Substance is freely filtered and fully excreted
Answer: b) Completely reabsorbed (no excretion)
Explanation: Clearance = 0 if no urinary excretion despite plasma presence.

Q14. Uricotelic animals primarily excrete nitrogen as:

a) Ammonia
b) Urea
c) Uric acid
d) Creatinine
Answer: c) Uric acid
Explanation: Birds/reptiles excrete uric acid — low water loss; fish/amphibians often ammonotelic.

Q15. Main site of amino acid reabsorption is:

a) Proximal tubule
b) Loop of Henle
c) Collecting duct
d) Distal tubule
Answer: a) Proximal tubule
Explanation: PCT actively reabsorbs most amino acids via transporters.

Q16. The peritubular capillaries and vasa recta function primarily in:

a) Filtration only
b) Reabsorption and maintaining medullary gradient (vasa recta as countercurrent exchanger)
c) Production of ADH
d) Producing urine directly
Answer: b) Reabsorption & medullary gradient maintenance
Explanation: Peritubular capillaries reclaim reabsorbed solutes/water; vasa recta preserve osmotic gradient.

Q17. Which diuretic acts by inhibiting Na⁺-K⁺-2Cl⁻ cotransporter in thick ascending limb?

a) Thiazides
b) Loop diuretics (e.g., furosemide)
c) Potassium-sparing (amiloride)
d) Carbonic anhydrase inhibitors
Answer: b) Loop diuretics
Explanation: Loop diuretics block NKCC2 → strong natriuresis and diuresis.

Q18. Carbonic anhydrase inhibitors (acetazolamide) cause:

a) Alkalinization of urine and metabolic acidosis
b) Alkalinization of blood
c) Increased HCO₃⁻ reabsorption
d) Increased aldosterone
Answer: a) Alkalinization of urine and metabolic acidosis
Explanation: CAIs block HCO₃⁻ reabsorption in PCT → alkaline urine, systemic metabolic acidosis.

Q19. Renal threshold refers to:

a) Plasma level above which a substance begins to be secreted
b) Plasma level above which substance appears in urine because transport maximum exceeded
c) Minimum urine volume produced per day
d) BP needed to start filtration
Answer: b) Plasma level above which substance appears in urine
Explanation: E.g., glucose renal threshold; above it, reabsorption saturates → glucosuria.

Q20. Clearance of inulin is used to measure:

a) Renal plasma flow (RPF)
b) Glomerular filtration rate (GFR)
c) Tubular secretion rate
d) Urine osmolality
Answer: b) GFR
Explanation: Inulin is freely filtered, not secreted/reabsorbed → clearance = GFR.

Q21. Para-aminohippuric acid (PAH) clearance approximates:

a) GFR
b) Renal plasma flow (RPF)
c) Filtration fraction
d) Tubular maximum
Answer: b) RPF
Explanation: PAH is filtered and secreted so nearly all PAH entering kidney is excreted → clearance ≈ RPF.

Q22. Filtration barrier excludes molecules mainly by:

a) Size and negative charge (basement membrane repels negatively charged proteins)
b) Active transport only
c) pH only
d) Temperature
Answer: a) Size & negative charge
Explanation: Large and negatively charged proteins (albumin) are repelled; small neutral molecules filter.

Q23. Proteinuria (albumin in urine) suggests damage to:

a) Proximal tubule only
b) Glomerular filtration barrier (glomerulonephritis)
c) Collecting duct only
d) Ureter
Answer: b) Glomerular filtration barrier
Explanation: Loss of charge/size selectivity → albuminuria; PCT defects cause aminoaciduria more.

Q24. Micturition reflex is coordinated by:

a) Spinal cord and pontine micturition center with parasympathetic activation
b) Only cortical centers
c) Only sympathetic activation
d) Kidney cortex
Answer: a) Spinal cord and pontine center with parasympathetic activation
Explanation: Stretch receptors → spinal & pontine centers → parasympathetic efferents to detrusor contraction and internal sphincter relaxation; cortical control modulates.

Q25. Urine typical healthy pH is:

a) Around 7.4 always
b) Variable, typically 4.5–8 depending on diet and metabolism
c) Exactly 6.8 only
d) Always alkaline
Answer: b) Variable, typically 4.5–8
Explanation: Diet, acid-base status, infections influence urine pH; normal range ~4.5–8.

Part 2 — Q26–Q50

Q26. The major buffer in extracellular fluid is:

a) Hemoglobin
b) Carbonic acid–bicarbonate system
c) Phosphate buffer only
d) Proteins only
Answer: b) Carbonic acid–bicarbonate system
Explanation: H₂CO₃/HCO₃⁻ buffer in plasma; CO₂ ventilation links respiratory & metabolic buffering.

Q27. Ammoniagenesis in the kidney contributes to:

a) Urea reabsorption
b) Acid excretion (NH₄⁺ formation) and pH regulation
c) Glucose formation only
d) Increase in blood K⁺ exclusively
Answer: b) Acid excretion and pH regulation
Explanation: PCT generates NH₃ which combines with H⁺ to excrete NH₄⁺, removing acid.

Q28. Renal medullary hypertonicity is essential for:

a) Glomerular filtration
b) Concentrating urine via water reabsorption in collecting duct
c) Secretion of aldosterone
d) Na⁺ secretion
Answer: b) Concentrating urine
Explanation: Medullary osmotic gradient (from loop of Henle and urea recycling) enables water reabsorption in presence of ADH.

Q29. Urea recycling helps to:

a) Dilute medullary interstitium
b) Maintain medullary osmotic gradient and conserve water
c) Excrete glucose
d) Inhibit ADH
Answer: b) Maintain medullary osmotic gradient
Explanation: Urea leaving inner medullary collecting duct increases interstitial osmolarity boosting water reabsorption.

Q30. Functional unit of kidney is:

a) Nephron (glomerulus + tubule)
b) Lobule
c) Alveolus
d) Hepatocyte
Answer: a) Nephron
Explanation: Each nephron filters and processes fluid; multiple nephrons form kidney function.

Q31. Glomerular capillary hydrostatic pressure (Pc) is increased by:

a) Dilating afferent arteriole
b) Constricting afferent arteriole
c) Dilating efferent arteriole
d) Decreasing renal blood flow
Answer: a) Dilating afferent arteriole
Explanation: Afferent dilation increases glomerular blood flow and Pc; efferent constriction also increases Pc.

Q32. Which statement about macula densa is true?

a) It secretes ADH
b) It senses NaCl concentration in distal tubule and modulates renin release (tubuloglomerular feedback)
c) It produces erythropoietin
d) It is in the collecting duct
Answer: b) Senses NaCl and modulates renin
Explanation: Macula densa (part of JGA) senses tubular NaCl → influences afferent arteriole tone and JG renin release.

Q33. The fraction of plasma that becomes filtrate (GFR/RPF) is called:

a) Filtration fraction (~20%)
b) Renal fraction
c) Reabsorption fraction
d) Secretion fraction
Answer: a) Filtration fraction (~20%)
Explanation: FF = GFR/RPF ≈ 0.2; indicates portion of plasma filtered per pass.

Q34. A rise in plasma protein (albumin) lowers GFR by:

a) Increasing capillary hydrostatic pressure
b) Increasing plasma oncotic pressure opposing filtration
c) Increasing filtration coefficient
d) Increasing afferent arteriole tone
Answer: b) Increasing plasma oncotic pressure
Explanation: Higher πp pulls fluid into capillary → less net filtration.

Q35. BUN (blood urea nitrogen) increases in:

a) Renal failure (decreased GFR) and dehydration
b) Excess hydration only
c) Low protein diet only
d) Increased GFR
Answer: a) Renal failure and dehydration
Explanation: Reduced excretion or increased reabsorption increases BUN.

Q36. The main excretory route for creatinine is:

a) Metabolism in liver
b) Glomerular filtration (and slight tubular secretion)
c) Reabsorption in PCT
d) Excretion via lungs
Answer: b) Filtration (minor secretion)
Explanation: Creatinine is useful GFR marker; small tubular secretion exists.

Q37. Which part of nephron is impermeable to water under low ADH?

a) Descending limb
b) Thin ascending limb and thick ascending limb (TAL)
c) Proximal tubule
d) Collecting duct with ADH present
Answer: b) Ascending limb (TAL)
Explanation: TAL actively reabsorbs NaCl but is water-impermeable, diluting tubular fluid.

Q38. Renal autoregulation maintains GFR over a range of BPs mainly by:

a) Myogenic response and tubuloglomerular feedback
b) Hormonal control only
c) Sympathetic blockade only
d) Changing filtration coefficient only
Answer: a) Myogenic response & tubuloglomerular feedback
Explanation: Afferent arteriole constriction/dilation and macula densa responses stabilize GFR.

Q39. Fanconi syndrome involves:

a) Loss of PCT reabsorptive function → glucosuria, aminoaciduria, phosphaturia
b) Increase in GFR only
c) Lack of ADH production
d) Hyperaldosteronism
Answer: a) Loss of PCT reabsorption
Explanation: Generalized proximal tubule dysfunction → multiple solute losses.

Q40. Nephrotic syndrome is characterized by:

a) Massive proteinuria, hypoalbuminemia, edema, hyperlipidemia
b) Hematuria only
c) Increased GFR only
d) Dehydration only
Answer: a) Massive proteinuria etc.
Explanation: Glomerular damage causing heavy protein loss → low oncotic pressure → edema.

Q41. Loop diuretics cause:

a) Increased Ca²⁺ reabsorption → hypercalcemia
b) Increased Ca²⁺ and Mg²⁺ excretion (hypocalcemia)
c) No effect on ion handling
d) Aldosterone-like effects
Answer: b) Increased Ca²⁺ & Mg²⁺ excretion
Explanation: Blocking NKCC disrupts lumen-positive potential → reduces paracellular Ca²⁺/Mg²⁺ reabsorption.

Q42. Thiazide diuretics cause:

a) Increased urinary Ca²⁺ excretion
b) Reduced urinary Ca²⁺ excretion (can cause hypercalcemia)
c) Block ENaC directly
d) Potent natriuresis in TAL
Answer: b) Reduced urinary Ca²⁺ excretion
Explanation: Thiazides increase distal Ca²⁺ reabsorption → lower urinary Ca²⁺.

Q43. The primary function of the loop of Henle is to:

a) Reabsorb glucose
b) Create medullary osmotic gradient for urine concentration
c) Secrete hormones
d) Produce renin
Answer: b) Create medullary gradient
Explanation: Countercurrent multiplication in loop establishes hyperosmotic medulla.

Q44. Intrarenal (within kidney) production of EPO increases in:

a) Hyperoxia
b) Hypoxia (low renal O₂ delivery)
c) Increased GFR
d) High PO₂ only
Answer: b) Hypoxia
Explanation: Kidney senses low O₂ → peritubular fibroblasts secrete EPO → RBC production.

Q45. Clearance of substance X equals (Ux × V) / Px. Here Ux is urine concentration, V urine flow, Px plasma concentration. This formula is:

a) True for any substance excreted only by glomerular filtration
b) False
c) Only for PAH
d) Only for protein
Answer: a) True for any substance
Explanation: Clearance formula applies generally; for specific uses (inulin for GFR, PAH for RPF).

Q46. Renal plasma flow can be calculated from PAH clearance because:

a) PAH is neither filtered nor secreted
b) PAH is filtered and actively secreted so almost all entering is excreted in one pass
c) PAH is reabsorbed completely
d) PAH measures GFR only
Answer: b) Filtered and secreted → excreted almost all
Explanation: PAH clearance ≈ effective renal plasma flow under low plasma PAH.

Q47. Which of the following increases urine concentration?

a) Low ADH
b) High ADH and intact medullary gradient
c) Absence of urea recycling
d) Diuretics blocking TAL NKCC only
Answer: b) High ADH and intact medullary gradient
Explanation: ADH increases CD water permeability; medullary gradient enables reabsorption → concentrated urine.

Q48. Renal handling of potassium: high dietary K⁺ leads to:

a) Decreased aldosterone → more K⁺ retention
b) Increased aldosterone → increased K⁺ secretion in cortical collecting duct
c) No change
d) Decreased urinary K⁺ excretion
Answer: b) Increased aldosterone → more K⁺ secretion
Explanation: Aldosterone stimulated by hyperkalemia increases principal cell K⁺ secretion.

Q49. Alkalosis tends to cause which change in K⁺ distribution?

a) Shift K⁺ into cells → hypokalemia
b) Shift K⁺ out of cells → hyperkalemia
c) No change
d) K⁺ excreted in breath
Answer: a) K⁺ shift into cells → hypokalemia
Explanation: Alkalosis increases H⁺ exit from cells, K⁺ moves intracellularly to maintain electroneutrality.

Q50. Renal tubular maximum (Tm) refers to:

a) Maximum filtration rate
b) Maximum reabsorptive capacity of transporters for a substance (e.g., glucose)
c) Maximum urine concentration only
d) Maximal GFR possible
Answer: b) Maximum reabsorptive capacity
Explanation: When filtered load > Tm, substance appears in urine (e.g., glucose in diabetes).

Part 3 — Q51–Q75

Q51. The major excretory organ for volatile acids (CO₂) is:

a) Kidney
b) Liver
c) Lungs
d) Heart
Answer: c) Lungs
Explanation: Lungs excrete CO₂ (volatile acid); kidneys handle nonvolatile acids and H⁺/HCO₃⁻ balance.

Q52. Normal urine specific gravity indicates:

a) Very diluted urine always
b) Relation of urine density to water; varies with hydration and solute excretion (1.003–1.030 typical)
c) It’s always 1.000
d) Measures pH
Answer: b) Relation of density to water (1.003–1.030)
Explanation: Specific gravity reflects concentration of solutes; normal range depends on hydration.

Q53. Glomerular capillary wall consists of:

a) Fenestrated endothelium, basement membrane, podocyte layer
b) Simple squamous only
c) Keratinized epithelium
d) Cartilage
Answer: a) Fenestrated endothelium + BM + podocytes
Explanation: These three layers form the filtration barrier.

Q54. Water diuresis (large volumes of dilute urine) occurs when:

a) ADH high
b) ADH low (e.g., central diabetes insipidus)
c) Aldosterone high
d) Urea recycling increases
Answer: b) Low ADH
Explanation: Low ADH → collecting duct impermeable to water → dilute, high-volume urine.

Q55. In nephrogenic diabetes insipidus, the cause is:

a) Lack of ADH secretion from posterior pituitary
b) Kidneys unresponsive to ADH (V2 receptor/AQP defects)
c) Excess aldosterone
d) Excess ADH action
Answer: b) Kidneys unresponsive to ADH
Explanation: Nephrogenic DI = renal resistance to ADH (vs. central DI = ADH deficiency).

Q56. Urea excretion is increased by:

a) High protein diet and increased catabolism
b) Low protein intake only
c) Increased ADH exclusively
d) Low BUN
Answer: a) High protein diet
Explanation: Protein breakdown increases urea production and excretion.

Q57. The main route of excretion for conjugated bilirubin is:

a) Urine
b) Bile into feces
c) Exhalation
d) Sweat
Answer: b) Bile into feces
Explanation: Conjugated bilirubin is secreted into bile; some urobilinogen derivatives appear in urine.

Q58. Urea in urine can be recycled to medulla; a major urea transporter in inner medullary collecting duct is:

a) UT-A1
b) SGLT2
c) NKCC2
d) ENaC
Answer: a) UT-A1
Explanation: Urea transporters (UT-A) facilitate urea recycling contributing to medullary osmolarity.

Q59. Which of the following increases renal excretion of Na⁺ and water?

a) Aldosterone
b) Antidiuretic hormone
c) Atrial natriuretic peptide (ANP)
d) Angiotensin II
Answer: c) ANP
Explanation: ANP promotes natriuresis and diuresis, lowering blood volume/pressure.

Q60. Proximal tubule reabsorbs approximately:

a) 65–70% of filtered Na⁺ and water, nearly all glucose and amino acids
b) 10% of Na⁺ only
c) No water
d) Only urea
Answer: a) 65–70% Na⁺ & water, all glucose/amino acids
Explanation: PCT reclaims bulk of filtrate via isoosmotic reabsorption.

Q61. Hemodialysis primarily removes toxins by:

a) Active secretion across membrane
b) Diffusion across semipermeable membrane driven by concentration gradients plus ultrafiltration
c) Increasing ADH
d) Enzymatic breakdown in dialyzer
Answer: b) Diffusion & ultrafiltration
Explanation: Solutes diffuse across dialyzer membrane; fluid removed by pressure gradient.

Q62. Peritoneal dialysis differs from hemodialysis because:

a) It uses peritoneal membrane as dialyzing surface and can be continuous at home
b) It requires extracorporeal blood circuit only
c) It removes proteins primarily
d) It is only for liver failure
Answer: a) Uses peritoneal membrane
Explanation: Dialysis fluid in peritoneal cavity exchanges solutes across peritoneum.

Q63. Renal papilla drains into:

a) Minor calyx → major calyx → renal pelvis → ureter
b) Directly to bladder
c) Collecting duct only
d) Glomerulus
Answer: a) Minor calyx pathway
Explanation: Papillary ducts open into minor calyces; urine flows to ureter.

Q64. Ureter peristalsis is initiated by:

a) Renal pelvis stretch and autonomic innervation causing peristaltic waves
b) Voluntary control only
c) Skeletal muscle contractions
d) ADH only
Answer: a) Pelvis stretch & autonomic
Explanation: Rhythmic smooth muscle contractions propel urine to bladder.

Q65. Normal urine volume per day in adults is about:

a) 0.1–0.5 L
b) 1–2 L
c) 4–5 L
d) >10 L
Answer: b) 1–2 L
Explanation: Typical urine output ~1–2 L/day, depends on intake and ADH.

Q66. Oliguria refers to:

a) Excessive urine production (>3 L/day)
b) Low urine output (<400 mL/day)
c) No urine production at all
d) Frequent urination
Answer: b) Low urine output (<400 mL/day)
Explanation: Oliguria indicates impaired renal perfusion or obstruction.

Q67. Anuria is:

a) Normal urine output
b) Absence or very low urine output (<50 mL/day)
c) Increased urinary frequency
d) Blood in urine
Answer: b) Absence/very low output
Explanation: Anuria indicates severe renal failure/complete obstruction.

Q68. Protein-free plasma water is filtered at Bowman’s capsule; large proteins are retained because:

a) They are lipophilic
b) Size and negative charge of basement membrane repels proteins (e.g., albumin)
c) Proteins are actively transported back into plasma
d) Proteins are dissolved in urine always
Answer: b) Size & negative charge
Explanation: Glomerular basement membrane and glycocalyx exclude large/negatively charged proteins.

Q69. The recurrent urinary tract infection risk increases with:

a) Short female urethra and vesicoureteral reflux
b) Male anatomy only
c) Having high GFR only
d) High urine pH only
Answer: a) Short female urethra & reflux
Explanation: Female urethra shortness & reflux predispose to ascending infections.

Q70. Kidney stones (renal calculi) are commonly composed of:

a) Cholesterol only
b) Calcium oxalate (most common), uric acid, struvite, cystine
c) Pure sodium chloride crystals
d) Proteins only
Answer: b) Calcium oxalate etc.
Explanation: Calcium stones (oxalate) most frequent; management depends on composition.

Q71. Hematuria (blood in urine) can be due to:

a) Glomerulonephritis, stones, infection, tumors, trauma
b) Only dehydration
c) Increased ADH only
d) High urine glucose only
Answer: a) GN, stones, infection, tumors, trauma
Explanation: Hematuria has many renal/urinary tract causes.

Q72. Renal tubular acidosis (RTA) involves:

a) Defect in H⁺ secretion or HCO₃⁻ reabsorption → metabolic acidosis with normal GFR
b) Elevated GFR only
c) Respiratory alkalosis
d) Excess urea excretion only
Answer: a) Defect in H⁺ secretion/HCO₃⁻ reabsorption
Explanation: RTAs are classified types I–IV based on site/function defect.

Q73. Loop diuretics may cause which electrolyte abnormality?

a) Hypokalemia, metabolic alkalosis, hypocalcemia, hypomagnesemia
b) Hyperkalemia only
c) Hypercalcemia only
d) No electrolyte changes
Answer: a) Hypokalemia, metabolic alkalosis, hypocalcemia, hypomagnesemia
Explanation: Loss of Na⁺ leads to increased distal Na⁺ reabsorption with K⁺ and H⁺ secretion; NKCC block affects Ca/Mg.

Q74. The renal capsule and perinephric fat function primarily as:

a) Hormone producers
b) Protective cushioning and support for kidney
c) Nephrons themselves
d) Sites of RBC production
Answer: b) Protective cushioning
Explanation: Fat & capsule protect and anchor kidneys.

Q75. Which enzyme converts angiotensin I to angiotensin II (active) mainly in lung endothelium?

a) Renin
b) ACE (angiotensin-converting enzyme)
c) Aldosterone synthase
d) Reninase
Answer: b) ACE
Explanation: ACE (in pulmonary endothelium) converts Ang I → Ang II, potent vasoconstrictor.

Part 4 — Q76–Q100

Q76. A decrease in effective circulating volume (e.g., hemorrhage) causes:

a) ↓ sympathetic activity → vasodilation
b) Activation of RAAS and sympathetic nervous system → vasoconstriction and Na⁺/water retention
c) Immediate increase in GFR only
d) Increased ANP release only
Answer: b) Activation of RAAS & SNS
Explanation: Compensatory responses increase vasoconstriction and fluid retention.

Q77. Urinary tract obstruction leading to hydronephrosis primarily causes:

a) Increased GFR always
b) Increased intratubular pressure and renal damage if prolonged
c) Immediate kidney hypertrophy only
d) Decreased blood urea only
Answer: b) ↑ intratubular pressure & renal damage
Explanation: Backpressure reduces GFR and damages nephrons.

Q78. Bicarbonate reabsorption in PCT involves which key enzyme?

a) ATP synthase
b) Carbonic anhydrase
c) Renin
d) Aldolase
Answer: b) Carbonic anhydrase
Explanation: Intracellular CA converts filtered HCO₃⁻ (via H⁺ secretion and CO₂ diffusion) facilitating reabsorption.

Q79. A rise in sympathetic tone to kidney causes:

a) Afferent arteriole dilation and ↑GFR
b) Afferent arteriole constriction → ↓RBF & ↓GFR (at high SNS)
c) Increased urine output always
d) Direct increase of ANP release
Answer: b) Afferent constriction → ↓RBF & ↓GFR
Explanation: Sympathetic vasoconstriction conserves fluid during stress.

Q80. Fanconi anemia is:

a) A proximal tubule reabsorptive defect (Fanconi syndrome)
b) A bone marrow failure syndrome (Fanconi anemia) — different condition
c) A renal stone disorder only
d) A liver disease
Answer: b) Bone marrow failure (Fanconi anemia)
Explanation: NOTE: Fanconi anemia (hematologic) ≠ Fanconi syndrome (renal PCT defect). Be careful in exams.

Q81. The majority of bicarbonate filtered is reabsorbed in:

a) PCT (~80–90%)
b) DCT only
c) Collecting duct only
d) Loop of Henle only
Answer: a) PCT
Explanation: PCT handles most HCO₃⁻ reclamation; DCT/CD fine-tune acid-base.

Q82. Renal glycosuria (glucose in urine with normal blood glucose) suggests:

a) Elevated plasma glucose always
b) Defect in proximal tubular glucose reabsorption (renal glycosuria)
c) Diabetes mellitus only
d) Increased ADH
Answer: b) Proximal tubular defect
Explanation: If plasma glucose normal but urine positive, suspect tubular reabsorption defect.

Q83. Which substance is a marker for tubular secretion (not filtration)?

a) Inulin
b) PAH (para-aminohippuric acid)
c) Glucose
d) Albumin
Answer: b) PAH
Explanation: PAH is filtered and secreted, so excreted amount approximates RPF.

Q84. The urinary bladder is lined by:

a) Transitional epithelium (urothelium) allowing stretch
b) Simple columnar epithelium only
c) Stratified squamous only
d) Pseudostratified ciliated columnar
Answer: a) Transitional epithelium
Explanation: Urothelium accommodates distension during filling.

Q85. Postrenal azotemia (elevated BUN/creatinine due to obstruction) is caused by:

a) Dehydration only
b) Urinary tract obstruction (e.g., stone) causing backpressure and decreased GFR
c) Increased protein intake only
d) Liver failure only
Answer: b) Urinary tract obstruction
Explanation: Blocked outflow increases tubular pressure and reduces excretion causing azotemia.

Q86. In chronic kidney disease, phosphate retention leads to:

a) Hypocalcemia and secondary hyperparathyroidism
b) Hypercalcemia only
c) Decreased PTH only
d) Increased vitamin D activation exclusively
Answer: a) Hypocalcemia & secondary hyperparathyroidism
Explanation: Reduced vitamin D activation and hyperphosphatemia lower Ca²⁺ → ↑PTH (renal osteodystrophy).

Q87. Which of the following increases renal HCO₃⁻ generation?

a) High bicarbonate diet only
b) Ammoniagenesis in PCT (NH₄⁺ excretion) helps generate new HCO₃⁻
c) Increased PCT reabsorption only
d) None of the above
Answer: b) Ammoniagenesis
Explanation: Excreting NH₄⁺ removes H⁺ and allows kidney to add new HCO₃⁻ to plasma.

Q88. The juxtaglomerular apparatus includes:

a) Macula densa, juxtaglomerular cells, and extraglomerular mesangial cells
b) Podocytes only
c) Bowman’s capsule only
d) Loop of Henle only
Answer: a) Macula densa, JG cells, extraglomerular mesangial cells
Explanation: JGA regulates renin via tubuloglomerular feedback.

Q89. A patient with nephrotic syndrome is likely to have:

a) Oliguria only
b) Massive proteinuria, hyperlipidemia, edema — increased risk of thrombosis & infection
c) Polyuria and hypernatremia only
d) No edema
Answer: b) Massive proteinuria etc.
Explanation: Loss of albumin reduces oncotic pressure causing edema and hyperlipidemia as liver synthesizes lipoproteins.

Q90. Which is NOT normally present in urine?

a) Urea
b) Creatinine
c) Glucose (in healthy fasting individual)
d) Uric acid
Answer: c) Glucose
Explanation: Glucose in urine indicates hyperglycemia or renal glycosuria; normally negligible.

Q91. Fractional excretion of sodium (FENa) is useful clinically to differentiate:

a) Prerenal azotemia (low FENa <1%) from intrinsic renal failure (higher FENa >2%)
b) Diabetes vs. hypertension
c) Liver vs. spleen disease
d) Type I vs. Type II diabetes
Answer: a) Prerenal vs intrinsic renal failure
Explanation: Prerenal states conserve sodium (low FENa); tubular damage causes higher sodium loss.

Q92. In acidemia (low blood pH), kidney response includes:

a) Increased H⁺ secretion, increased NH₄⁺ excretion, increased HCO₃⁻ reclamation/generation
b) Decreased H⁺ secretion only
c) Immediate lung compensation only
d) No renal role
Answer: a) Increased H⁺ secretion & NH₄⁺ excretion
Explanation: Kidneys correct metabolic acidosis slowly by excreting acid and generating HCO₃⁻.

Q93. Which urinary constituent is measured to assess hydration and concentrating ability?

a) Urine ketones only
b) Urine specific gravity and osmolality
c) Blood glucose only
d) Serum creatinine only
Answer: b) Urine specific gravity and osmolality
Explanation: These reflect urine concentration and kidney concentrating capacity.

Q94. Urinary casts (e.g., RBC casts) indicate:

a) Lower urinary tract infection only
b) Tubular or glomerular disease — RBC casts indicate glomerulonephritis
c) No pathology always
d) High urine flow only
Answer: b) Tubular or glomerular disease
Explanation: Casts form in tubules; RBC casts point to glomerular bleeding.

Q95. The renal threshold for phosphate is:

a) Fixed irrespective of PTH
b) Lowered by PTH causing phosphaturia
c) Increased by PTH causing phosphate retention
d) Unrelated to hormones
Answer: b) Lowered by PTH
Explanation: PTH reduces PCT phosphate reabsorption → increased phosphate excretion.

Q96. The action of aldosterone in kidney is to:

a) Increase Na⁺ reabsorption and K⁺ secretion via principal cells in collecting duct
b) Block ENaC channels
c) Inhibit Na⁺/K⁺-ATPase
d) Increase ADH secretion only
Answer: a) Increase Na⁺ reabsorption & K⁺ secretion
Explanation: Aldosterone upregulates ENaC and Na⁺/K⁺-ATPase expression.

Q97. The main effect of ANP on renal function is:

a) Increase sodium retention
b) Decrease GFR
c) Dilate afferent arteriole and constrict efferent arteriole → increase GFR and natriuresis
d) Increase aldosterone release
Answer: c) Increase GFR and natriuresis
Explanation: ANP dilates afferent, constricts efferent, reduces Na⁺ reabsorption → diuresis.

Q98. Creatinine is produced from:

a) Glucose metabolism only
b) Muscle creatine breakdown (creatine phosphate)
c) Dietary fat breakdown
d) Hepatic urea cycle directly
Answer: b) Muscle creatine breakdown
Explanation: Creatine phosphate spontaneously forms creatinine; constant production proportional to muscle mass.

Q99. Which is true about neonatal kidneys compared to adults?

a) Newborns have higher GFR per body surface area than adults
b) Newborn kidneys have lower concentrating ability due to immature medullary gradient and low ADH response
c) Neonates cannot excrete urea
d) Neonatal kidneys are identical to adults
Answer: b) Lower concentrating ability
Explanation: Neonates have limited concentrating ability; GFR is lower and rises with age.

Q100. The presence of glucose, ketones, and low pH in urine suggests:

a) Starvation only
b) Diabetic ketoacidosis (DKA) — uncontrolled diabetes causing glucosuria, ketonuria, metabolic acidosis
c) Renal glycosuria only
d) Liver failure only
Answer: b) Diabetic ketoacidosis
Explanation: Hyperglycemia → glucosuria; lipolysis → ketones; metabolic acidosis → low blood pH.

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