Multiple-choice questions (MCQs) prepared according to the PCI B. Pharm syllabus and MCQs on the Urinary System (Kidney Physiology)

Quick Revision Notes: Urinary System

1. Anatomy of the Urinary Tract

Remember the Path of Urine

Kidneys → Ureters → Urinary Bladder → Urethra

Functions

• Kidneys: Filter blood and produce urine.

• Ureters: Carry urine to the bladder.

• Urinary bladder: Temporarily stores urine.

• Urethra: Expels urine from the body.

Exam Fact

• Normal urine output: 1–2 L/day

Mnemonic: KUBU
Kidney → Ureter → Bladder → Urethra

2. Kidney Anatomy

Each kidney is:

• Bean-shaped

• Reddish-brown

• Located behind the peritoneum (retroperitoneal)

• Protected by the lower ribs

Parts of the Kidney

• Cortex: Outer region; contains glomeruli.

• Medulla: Inner region; contains renal pyramids.

• Renal pelvis: Funnel-shaped collecting chamber.

• Hilum: Entry and exit point for renal artery, renal vein, ureter, lymphatics, and nerves.

Exam Fact

• Right kidney is slightly lower than the left because of the liver.

Mnemonic: Come Meet People
Cortex → Medulla → Pelvis

3. Nephron – Functional Unit of the Kidney

• Each kidney contains about 1 million nephrons.

Parts of a Nephron

1. Glomerulus

2. Bowman's capsule

3. Proximal convoluted tubule (PCT)

4. Loop of Henle

5. Distal convoluted tubule (DCT)

6. Collecting duct

Easy Function Table

• Part Main Function

• Glomerulus Filtration

• PCT Maximum reabsorption

• Loop of Henle Concentrates urine

• DCT Hormonal regulation

• Collecting duct Final water reabsorption

Mnemonic:
Good Boys Prefer Long Daily Coffee

• Glomerulus

• Bowman's capsule

• PCT

• Loop of Henle

• DCT

• Collecting duct

4. Functions of the Kidney

The kidneys perform several vital functions:

• Remove metabolic waste products

• Maintain water balance

• Regulate electrolytes

• Control blood pressure

• Maintain acid–base balance

• Produce erythropoietin

• Activate vitamin D

Mnemonic: WE BAE

• Water balance

• Electrolytes

• Blood pressure

• Acid–base balance

• Erythropoietin (and active vitamin D)

5. Urine Formation

Urine formation occurs in three steps:

Step 1 – Glomerular Filtration

Blood is filtered through the glomerulus.

Step 2 – Tubular Reabsorption

Useful substances return to the blood:

• Water

• Glucose

• Amino acids

• Sodium

Step 3 – Tubular Secretion

Additional wastes and excess ions are secreted into the tubule:

• H⁺

• K⁺

• Ammonium

• Drugs

Mnemonic: FRS
Filtration → Reabsorption → Secretion

6. Important Hormones Acting on the Kidney

ADH (Antidiuretic Hormone)

• Acts on the collecting ducts.

• Increases water reabsorption.

• Produces concentrated urine.

Aldosterone

• Acts mainly on the distal tubule and collecting duct.

• Increases sodium reabsorption.

• Increases potassium excretion.

ANP (Atrial Natriuretic Peptide)

• Promotes sodium and water excretion.

• Lowers blood pressure.

Mnemonic: ADA

• ADH → Adds water

• D (Aldosterone) → Drives sodium retention

• ANP → Allows sodium loss

7. Micturition Reflex

The micturition reflex is the process of urination.

Sequence

Bladder fills
→ Stretch receptors are activated
→ Sacral spinal cord (S2–S4)
→ Detrusor muscle contracts
→ Internal sphincter relaxes
→ External sphincter relaxes voluntarily
→ Urination occurs

Exam Fact

• Parasympathetic nerves initiate micturition.

• External urethral sphincter is under voluntary control.

Mnemonic: Fill–Stretch–Spinal–Squeeze–Urinate

8. Kidney in Acid–Base Balance

The kidneys help maintain normal blood pH (7.35–7.45) by:

• Excreting hydrogen ions (H⁺)

• Reabsorbing bicarbonate (HCO₃⁻)

• Producing new bicarbonate when needed

Easy Rule

• Acid out

• Bicarbonate in

9. Renin–Angiotensin–Aldosterone System (RAAS)

Sequence

↓ Blood pressure
→ Kidney releases Renin
→ Angiotensinogen → Angiotensin I
→ ACE converts Angiotensin I → Angiotensin II
→ Blood vessels constrict
→ Aldosterone is released
→ Sodium and water are reabsorbed
→ Blood pressure increases

Mnemonic: RAAS = Raise Arterial Pressure

• Renin

• Angiotensin II

• Aldosterone

• Sodium & water retention

10. Exam Facts

• Functional unit of kidney = Nephron

• Number of nephrons per kidney ≈ 1 million

• GFR ≈ 125 mL/min

• Normal urine output = 1–2 L/day

• Filtration occurs in the glomerulus

• Maximum reabsorption occurs in the PCT

• ADH acts mainly on the Collecting duct

• Aldosterone increases Na⁺ reabsorption and K⁺ excretion

• Micturition center = S2–S4

• ACE is mainly present in the lungs

• Renin is released by juxtaglomerular cells

• Blood pH = 7.35–7.45

One-Line Revision

• Kidneys filter blood and form urine.

• The nephron is the functional unit of the kidney.

• Urine formation = Filtration → Reabsorption → Secretion.

• PCT performs maximum reabsorption.

• The loop of Henle concentrates urine.

• ADH conserves water.

• Aldosterone conserves sodium.

• Parasympathetic nerves control urination.

• Kidneys maintain acid–base balance by excreting H⁺ and conserving HCO₃⁻.

• RAAS increases blood pressure by promoting vasoconstriction and sodium–water retention.

MCQs

1. The urinary system consists of:

A. Kidneys, ureters, urinary bladder, and urethra
B. Kidneys, liver, bladder, and urethra
C. Kidneys, spleen, ureters, and bladder
D. Kidneys, pancreas, bladder, and urethra

Answer: A

2. The functional unit of the kidney is

A. Alveolus
B. Neuron
C. Nephron
D. Glomerulus

Answer: C

3. An adult human kidney contains approximately

A. 10,000 nephrons
B. 100,000 nephrons
C. 1 million nephrons
D. 10 million nephrons

Answer: C

4. The right kidney is slightly lower than the left because of the

A. Spleen
B. Stomach
C. Liver
D. Pancreas

Answer: C

5. The outer region of the kidney is called

A. Medulla
B. Cortex
C. Pelvis
D. Hilum

Answer: B

6. Which structure carries urine from the kidney to the urinary bladder?

A. Urethra
B. Renal artery
C. Ureter
D. Renal vein

Answer: C

7. The renal pelvis is formed by the union of

A. Nephrons
B. Major calyces
C. Minor calyces
D. Collecting ducts

Answer: B

8. The hilum of the kidney transmits all EXCEPT

A. Renal artery
B. Renal vein
C. Ureter
D. Inferior vena cava

Answer: D

Anatomy of the Nephron

9. Filtration of blood occurs in the

A. Collecting duct
B. Loop of Henle
C. Glomerulus
D. Distal convoluted tubule

Answer: C

10. The Bowman's capsule surrounds the

A. Loop of Henle
B. Glomerulus
C. Collecting duct
D. Proximal tubule

Answer: B

11. Maximum reabsorption of glucose occurs in the

A. Distal convoluted tubule
B. Collecting duct
C. Proximal convoluted tubule
D. Loop of Henle

Answer: C

12. The descending limb of the loop of Henle is mainly permeable to

A. Sodium
B. Chloride
C. Water
D. Potassium

Answer: C

13. The ascending limb of the loop of Henle is impermeable to

A. Sodium
B. Chloride
C. Potassium
D. Water

Answer: D

14. Juxtaglomerular cells secrete

A. ADH
B. Renin
C. Aldosterone
D. ANP

Answer: B

15. The macula densa is located in the

A. Bowman's capsule
B. Proximal convoluted tubule
C. Distal convoluted tubule
D. Collecting duct

Answer: C

Functions of the Kidney

16. Which is NOT a function of the kidney?

A. Regulation of blood pressure
B. Erythropoietin secretion
C. Insulin production
D. Acid-base balance

Answer: C

17. Erythropoietin stimulates

A. Platelet formation
B. RBC production
C. WBC production
D. Plasma protein synthesis

Answer: B

18. Active vitamin D is formed in the

A. Liver
B. Kidney
C. Skin
D. Pancreas

Answer: B

19. The kidneys regulate blood pressure primarily through

A. ADH only
B. RAAS
C. Insulin
D. Thyroxine

Answer: B

20. The normal daily urine output in adults is approximately

A. 100–300 mL
B. 500–800 mL
C. 1–2 L
D. 4–5 L

Answer: C

Physiology of Urine Formation

21. Urine formation occurs in

A. Two steps
B. Three steps
C. Four steps
D. Five steps

Answer: B

22. The three processes involved in urine formation are

A. Filtration, digestion, secretion
B. Filtration, reabsorption, secretion
C. Filtration, absorption, excretion
D. Reabsorption, diffusion, excretion

Answer: B

23. Glomerular filtration rate (GFR) in healthy adults is approximately

A. 30 mL/min
B. 60 mL/min
C. 125 mL/min
D. 250 mL/min

Answer: C

24. The filtration membrane consists of all EXCEPT

A. Fenestrated endothelium
B. Basement membrane
C. Podocytes
D. Smooth muscle layer

Answer: D

25. Most sodium is reabsorbed in the

A. Distal tubule
B. Collecting duct
C. Proximal tubule
D. Loop of Henle

Answer: C

26. Glucose appears in urine when blood glucose exceeds the renal threshold of approximately

A. 80 mg/dL
B. 120 mg/dL
C. 180 mg/dL
D. 250 mg/dL

Answer: C

27. ADH primarily acts on the

A. Bowman's capsule
B. Collecting duct
C. Proximal tubule
D. Glomerulus

Answer: B

28. Aldosterone increases

A. Sodium excretion
B. Potassium reabsorption
C. Sodium reabsorption
D. Water secretion

Answer: C

29. The micturition reflex is mainly controlled by:

A. Sympathetic nerves
B. Parasympathetic nerves
C. Somatic nerves
D. Cranial nerves

Answer: B

30. The spinal center for micturition is located in

A. Cervical cord
B. Thoracic cord
C. Sacral cord (S2–S4)
D. Lumbar cord

Answer: C

31. During urination, the detrusor muscle

A. Relaxes
B. Contracts
C. Remains inactive
D. Becomes rigid

Answer: B

32. The external urethral sphincter is under

A. Involuntary control only
B. Voluntary control
C. Hormonal control
D. Reflex control only

Answer: B

33. The kidneys regulate blood pH mainly by

A. Excreting bicarbonate only
B. Excreting H⁺ and reabsorbing bicarbonate
C. Producing hydrochloric acid
D. Secreting carbon dioxide

Answer: B

34. Which condition is compensated primarily by increased bicarbonate reabsorption?

A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic alkalosis
D. Hyperglycemia

Answer: A

35. The normal blood pH is

A. 6.8–7.0
B. 7.0–7.2
C. 7.35–7.45
D. 7.8–8.2

Answer: C

Renin–Angiotensin–Aldosterone System (RAAS)

36. Renin is released when

A. Blood pressure increases
B. Blood pressure decreases
C. Blood glucose increases
D. Plasma calcium increases

Answer: B

37. Renin converts

A. Angiotensin I to Angiotensin II
B. Angiotensinogen to Angiotensin I
C. Aldosterone to renin
D. ACE to angiotensin

Answer: B

38. Angiotensin-converting enzyme (ACE) mainly converts

A. Renin into aldosterone
B. Angiotensin I into Angiotensin II
C. Aldosterone into cortisol
D. Angiotensin II into renin

Answer: B

39. ACE is predominantly present in the

A. Liver
B. Kidney cortex
C. Lungs
D. Spleen

Answer: C

40. Angiotensin II causes

A. Vasodilation
B. Vasoconstriction
C. Bradycardia
D. Increased glucose uptake

Answer: B

41. Aldosterone is secreted from the

A. Adrenal medulla
B. Adrenal cortex
C. Pituitary gland
D. Thyroid gland

Answer: B

42. Aldosterone increases

A. Sodium excretion
B. Potassium retention
C. Sodium and water reabsorption
D. Calcium excretion

Answer: C

43. ACE inhibitors lower blood pressure primarily by

A. Increasing renin secretion
B. Blocking formation of Angiotensin II
C. Increasing aldosterone release
D. Increasing ADH secretion

Answer: B

44. Which part of the nephron is most susceptible to ischemic injury?

A. Bowman's capsule
B. Proximal convoluted tubule
C. Distal convoluted tubule
D. Collecting duct

Answer: B

45. Glomerular filtration depends mainly on

A. Osmotic pressure of urine
B. Net filtration pressure
C. Blood glucose concentration
D. Plasma protein synthesis

Answer: B

46. Which hormone increases water reabsorption without directly increasing sodium reabsorption?

A. Aldosterone
B. Renin
C. ADH
D. ANP

Answer: C

47. The major nitrogenous waste excreted in human urine is:

A. Uric acid
B. Creatinine
C. Urea
D. Ammonia

Answer: C

48. The hormone that opposes the action of the RAAS is

A. ADH
B. ANP
C. Renin
D. Cortisol

Answer: B

49. Creatinine clearance is commonly used to estimate

A. Urine pH
B. Renal plasma flow
C. Glomerular filtration rate
D. Tubular secretion

Answer: C

50. Which of the following is the correct sequence of urine flow?

A. Kidney → Ureter → Bladder → Urethra
B. Kidney → Bladder → Ureter → Urethra
C. Kidney → Urethra → Bladder → Ureter
D. Kidney → Ureter → Urethra → Bladder

Answer: A

Exam Tips

These topics are frequently tested in GPAT, NIPER, AIIMS Pharmacist, ESIC, SSC, Railway Pharmacist, and State Pharmacist examinations:

• Anatomy of the nephron and kidney

• Functions of different nephron segments

• Glomerular filtration rate (GFR)

• Tubular reabsorption and secretion

• Hormonal regulation (ADH, Aldosterone, ANP)

• Renin–Angiotensin–Aldosterone System (RAAS)

• Micturition reflex (S2–S4 spinal center)

• Acid–base regulation by the kidneys

• Creatinine clearance and renal physiology

• Clinical applications of ACE inhibitors and RAAS physiology

Dr. Alok Singh