Human excretory system (structure and function) MCQs With Answer

Human excretory system (structure and function) MCQs With Answer is an essential revision resource for B. Pharm students preparing for pharmacology, physiology, and clinical pharmacy exams. This concise, keyword-rich guide covers renal anatomy, nephron structure, glomerular filtration, tubular reabsorption/secretion, acid–base balance, renal hormones (ADH, aldosterone, renin), clearance concepts (GFR, RPF, creatinine, PAH), diuretics mechanisms, and drug dosing in renal impairment. Emphasis on pathophysiology, pharmacologic targets, and clinical correlations helps strengthen understanding for therapeutics and drug safety. Clear MCQs with explanations reinforce core concepts and drug–kidney interactions. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which organ is the primary excretory organ responsible for regulating volume, electrolytes, and acid–base balance?

• Liver
• Lungs
• Skin
• Kidneys

Correct Answer: Kidneys

Q2. Which functional unit of the kidney is responsible for urine formation?

• Collecting duct
• Nephron
• Renal pelvis
• Calyx

Correct Answer: Nephron

Q3. The filtration barrier in the glomerulus consists of three layers. Which of the following is NOT one of them?

• Fenestrated endothelium
• Basement membrane
• Podocyte slit diaphragm
• Bowman’s capsule epithelial basement

Correct Answer: Bowman’s capsule epithelial basement

Q4. Which nephron segment is impermeable to water but actively reabsorbs Na+, K+, and Cl- via NKCC2?

• Proximal convoluted tubule
• Thin descending limb
• Thick ascending limb of loop of Henle
• Collecting duct

Correct Answer: Thick ascending limb of loop of Henle

Q5. Which process primarily occurs at the glomerulus?

• Tubular secretion
• Tubular reabsorption
• Ultrafiltration (glomerular filtration)
• Concentration of urine

Correct Answer: Ultrafiltration (glomerular filtration)

Q6. Which equation or concept directly represents net glomerular filtration pressure determinants?

• Starling forces across peritubular capillaries
• Starling forces across glomerular capillaries
• Henderson–Hasselbalch equation
• Fick’s law of diffusion

Correct Answer: Starling forces across glomerular capillaries

Q7. Which measurement is the gold standard for measuring true GFR experimentally?

• Serum creatinine concentration
• Creatinine clearance
• Inulin clearance
• PAH clearance

Correct Answer: Inulin clearance

Q8. PAH clearance is used clinically to estimate which parameter?

• GFR
• Renal plasma flow (effective)**
• Urine osmolality
• Filtration fraction

Correct Answer: Renal plasma flow (effective)**

Q9. Filtration fraction is defined as:

• RPF / GFR
• GFR / RPF
• Urine flow / plasma flow
• PAH clearance / inulin clearance

Correct Answer: GFR / RPF

Q10. Which hormone increases water reabsorption in the collecting duct by inserting aquaporin-2 channels?

• Aldosterone
• Parathyroid hormone
• Antidiuretic hormone (ADH, vasopressin)
• Atrial natriuretic peptide (ANP)

Correct Answer: Antidiuretic hormone (ADH, vasopressin)

Q11. Aldosterone acts primarily on which cells to increase Na+ reabsorption and K+ secretion?

• Proximal tubule cells
• Loop of Henle cells
• Principal cells of the collecting duct
• Intercalated cells of collecting duct

Correct Answer: Principal cells of the collecting duct

Q12. Which diuretic inhibits carbonic anhydrase in the proximal tubule, leading to bicarbonate diuresis?

• Furosemide
• Hydrochlorothiazide
• Acetazolamide
• Spironolactone

Correct Answer: Acetazolamide

Q13. Loop diuretics (e.g., furosemide) increase excretion of which electrolyte most prominently?

• Calcium reabsorption (increased)
• Calcium excretion (increased)
• Sodium reabsorption (increased)
• Magnesium reabsorption (increased)

Correct Answer: Calcium excretion (increased)

Q14. Thiazide diuretics affect calcium handling by the kidney in what way?

• Increase urinary calcium excretion
• Reduce urinary calcium excretion (increase reabsorption)
• No effect on calcium handling
• Cause hypercalcemia by bone resorption only

Correct Answer: Reduce urinary calcium excretion (increase reabsorption)

Q15. The juxtaglomerular cells secrete renin in response to which stimulus?

• Increased afferent arteriole pressure
• Increased NaCl delivery to macula densa
• Decreased afferent arteriole pressure and decreased NaCl at macula densa
• High extracellular K+ only

Correct Answer: Decreased afferent arteriole pressure and decreased NaCl at macula densa

Q16. Angiotensin II preferentially constricts which arteriolar segment in the glomerulus to preserve GFR?

• Afferent arteriole
• Efferent arteriole
• Peritubular capillaries only
• Interlobular artery

Correct Answer: Efferent arteriole

Q17. Which drug class can reduce glomerular filtration pressure by dilating the efferent arteriole through RAAS blockade?

• Loop diuretics
• ACE inhibitors / ARBs
• Thiazide diuretics
• Calcium channel blockers

Correct Answer: ACE inhibitors / ARBs

Q18. Which statement best describes countercurrent multiplication in the kidney?

• It occurs in cortical nephrons only
• It establishes a medullary osmotic gradient using loop of Henle and vasa recta
• It refers to secretion of H+ against a gradient
• It is the mechanism of aldosterone release

Correct Answer: It establishes a medullary osmotic gradient using loop of Henle and vasa recta

Q19. Urea recycling contributes to the medullary osmotic gradient. Which segment is primarily involved in urea recycling?

• Proximal tubule
• Thin descending limb of loop of Henle
• Collecting duct and inner medulla
• Distal convoluted tubule

Correct Answer: Collecting duct and inner medulla

Q20. Which laboratory measure is most useful for estimating renal function for drug dosing in adults?

• Serum potassium
• Urine specific gravity
• Estimated creatinine clearance or eGFR (Cockcroft–Gault or MDRD/eGFR)
• Blood urea nitrogen alone

Correct Answer: Estimated creatinine clearance or eGFR (Cockcroft–Gault or MDRD/eGFR)

Q21. Which tissue synthesizes erythropoietin in the adult kidney?

• Glomerular endothelial cells
• Proximal tubule epithelial cells
• Interstitial fibroblast-like cells in the renal cortex
• Podocytes

Correct Answer: Interstitial fibroblast-like cells in the renal cortex

Q22. The major effect of atrial natriuretic peptide (ANP) on the kidney is:

• Increase Na+ reabsorption and water retention
• Increase glomerular filtration and decrease Na+ reabsorption
• Stimulate aldosterone release
• Stimulate ADH secretion

Correct Answer: Increase glomerular filtration and decrease Na+ reabsorption

Q23. Which drug class can cause afferent arteriole vasoconstriction by inhibiting renal prostaglandin synthesis and thus reduce GFR in hypovolemic patients?

• ACE inhibitors
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Beta-blockers
• Loop diuretics

Correct Answer: Nonsteroidal anti-inflammatory drugs (NSAIDs)

Q24. A serum BUN/creatinine ratio >20:1 typically suggests which condition?

• Intrinsic renal failure (acute tubular necrosis)
• Prerenal azotemia (decreased renal perfusion)
• Postrenal obstruction only
• Normal kidney function

Correct Answer: Prerenal azotemia (decreased renal perfusion)

Q25. Muddy brown granular casts in urine sediment are classically associated with which renal pathology?

• Acute tubular necrosis (ATN)
• Minimal change disease
• Nephrolithiasis
• Urinary tract infection

Correct Answer: Acute tubular necrosis (ATN)

Q26. Which renal transporter is the main target of thiazide diuretics?

• Na+/K+/2Cl- cotransporter (NKCC2)
• Na+/Cl- cotransporter (NCC) in distal convoluted tubule
• Epithelial sodium channel (ENaC)
• Carbonic anhydrase enzyme

Correct Answer: Na+/Cl- cotransporter (NCC) in distal convoluted tubule

Q27. Amiloride acts as a diuretic by blocking which channel?

• NKCC2 transporter
• Epithelial sodium channel (ENaC)
• Na+/K+ ATPase pump on basolateral membrane
• ROMK channel on apical membrane

Correct Answer: Epithelial sodium channel (ENaC)

Q28. Which type of renal tubular acidosis is characterized by impaired H+ secretion in the distal nephron leading to inability to acidify urine?

• Type 2 (proximal) RTA
• Type 1 (distal) RTA
• Type 4 RTA (hyperkalemic)
• Respiratory acidosis

Correct Answer: Type 1 (distal) RTA

Q29. Type 4 RTA is commonly associated with which electrolyte abnormality?

• Hypokalemia
• Hyperkalemia
• Hyponatremia only
• Hypocalcemia

Correct Answer: Hyperkalemia

Q30. Which renal process is mainly responsible for the generation of new bicarbonate during chronic metabolic acidosis?

• Reabsorption of filtered bicarbonate only
• Ammoniagenesis and titratable acid excretion in the proximal tubule
• Urea excretion in collecting duct
• Increased GFR

Correct Answer: Ammoniagenesis and titratable acid excretion in the proximal tubule

Q31. Cockcroft–Gault formula estimates creatinine clearance using which variables?

• Age, weight, serum creatinine, and sex
• Only serum creatinine and BUN
• Urine creatinine only
• GFR measured by inulin

Correct Answer: Age, weight, serum creatinine, and sex

Q32. Which statement about renal handling of drugs is correct?

• All drugs are filtered and excreted unchanged in urine
• Only lipophilic drugs are filtered at the glomerulus
• Drugs may be eliminated by filtration, secretion (e.g., via organic anion/cation transporters), and reabsorption
• Renal excretion is independent of urine pH

Correct Answer: Drugs may be eliminated by filtration, secretion (e.g., via organic anion/cation transporters), and reabsorption

Q33. Which renal transporter system is important for secretion of many organic anions including penicillins and PAH?

• Organic cation transporters (OCT)**
• Organic anion transporters (OAT)
• ENaC channels
• NKCC2 cotransporter

Correct Answer: Organic anion transporters (OAT)

Q34. Which common nephrotoxic antibiotic is most associated with acute tubular necrosis and proximal tubular dysfunction?

• Penicillin
• Aminoglycosides (e.g., gentamicin)**
• Ceftriaxone
• Vancomycin (never nephrotoxic)

Correct Answer: Aminoglycosides (e.g., gentamicin)

Q35. Which of the following is true about creatinine as a marker of GFR?

• Serum creatinine falls rapidly with early loss of GFR
• Creatinine is secreted slightly by tubules, so creatinine clearance slightly overestimates GFR
• Creatinine clearance dramatically underestimates GFR in all cases
• Creatinine is reabsorbed extensively in the tubules

Correct Answer: Creatinine is secreted slightly by tubules, so creatinine clearance slightly overestimates GFR

Q36. Which cell type forms the slit diaphragm critical for selective glomerular filtration?

• Endothelial cells
• Mesangial cells
• Podocytes (visceral epithelial cells)
• Parietal epithelial cells

Correct Answer: Podocytes (visceral epithelial cells)

Q37. Which of the following medications increases potassium retention by antagonizing aldosterone receptors?

• Furosemide
• Lisinopril
• Spironolactone
• Hydrochlorothiazide

Correct Answer: Spironolactone

Q38. Which parameter best differentiates prerenal azotemia from intrinsic renal failure (ATN) using urinary indices?

• Urine pH only
• Fractional excretion of sodium (FENa) — low in prerenal, high in ATN
• Serum potassium only
• Urine glucose presence

Correct Answer: Fractional excretion of sodium (FENa) — low in prerenal, high in ATN

Q39. Which mechanism explains why NSAIDs can precipitate renal failure in volume-depleted patients?

• They block aldosterone receptors causing hyperkalemia
• They inhibit prostaglandin synthesis, reducing afferent arteriole dilation and decreasing GFR
• They increase ADH release causing water retention
• They directly damage podocytes causing nephrotic syndrome

Correct Answer: They inhibit prostaglandin synthesis, reducing afferent arteriole dilation and decreasing GFR

Q40. The thin descending limb of Henle is highly permeable to which substance, facilitating water reabsorption?

• Sodium only
• Urea only
• Water (highly permeable)
• Glucose

Correct Answer: Water (highly permeable)

Q41. Which clinical indication is NOT a standard indication to initiate renal replacement therapy (dialysis)?

• Refractory hyperkalemia with ECG changes
• Volume overload refractory to diuretics
• Uremic pericarditis or encephalopathy
• Asymptomatic mild elevation of BUN with stable electrolytes

Correct Answer: Asymptomatic mild elevation of BUN with stable electrolytes

Q42. Chronic kidney disease staging primarily relies on which measurement?

• Serum calcium
• eGFR (estimated glomerular filtration rate)
• Urine color
• BUN only

Correct Answer: eGFR (estimated glomerular filtration rate)

Q43. Which of the following best describes the role of mesangial cells in the glomerulus?

• They form podocyte foot processes
• Provide structural support, contractility, and clearance of trapped residues in glomerular tuft
• Line Bowman’s space
• Secrete aldosterone locally

Correct Answer: Provide structural support, contractility, and clearance of trapped residues in glomerular tuft

Q44. Mannitol is used clinically as an osmotic diuretic. Its site and primary mechanism of action is:

• Inhibit NKCC2 in thick ascending limb
• Filtered at glomerulus and limits water reabsorption in proximal tubule and loop via osmotic effect
• Block ENaC in collecting duct
• Stimulate aldosterone secretion

Correct Answer: Filtered at glomerulus and limits water reabsorption in proximal tubule and loop via osmotic effect

Q45. 1-alpha-hydroxylase in the kidney activates vitamin D (calcitriol). Which hormone stimulates this enzyme?

• Insulin
• Parathyroid hormone (PTH)
• Aldosterone
• ADH

Correct Answer: Parathyroid hormone (PTH)

Q46. Which urinary finding is most suggestive of glomerular proteinuria rather than tubular proteinuria?

• Low-molecular-weight proteins in urine
• Selective albuminuria with oval fat bodies and fatty casts (nephrotic range proteinuria)
• Presence of glucose in urine
• Positive nitrite test only

Correct Answer: Selective albuminuria with oval fat bodies and fatty casts (nephrotic range proteinuria)

Q47. Which electrolyte disturbance is commonly caused by ACE inhibitors and ARBs due to decreased aldosterone?

• Hypokalemia
• Hyperkalemia
• Hyponatremia only
• Hypocalcemia

Correct Answer: Hyperkalemia

Q48. Which statement about the vasa recta is correct?

• They actively transport NaCl to create the medullary gradient
• They act as countercurrent exchangers to preserve the medullary osmotic gradient
• They are impermeable to water and solutes
• They have no role in concentrating urine

Correct Answer: They act as countercurrent exchangers to preserve the medullary osmotic gradient

Q49. In nephrotic syndrome, which consequence is commonly observed due to heavy proteinuria?

• Hypoalbuminemia leading to edema
• Metabolic alkalosis due to H+ loss in urine
• Hyperalbuminemia
• Increased oncotic pressure in plasma

Correct Answer: Hypoalbuminemia leading to edema

Q50. Which feature differentiates minimal change disease from membranous nephropathy on electron microscopy?

• Electron-dense subepithelial immune complex deposits in minimal change disease
• Effacement of foot processes without immune complex deposits in minimal change disease
• Subendothelial immune complex deposits in minimal change disease
• Thickened basement membrane with no podocyte changes in minimal change disease

Correct Answer: Effacement of foot processes without immune complex deposits in minimal change disease

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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