Part 6: Micturition & Role of Other Organs in Excretion

Part 6 (25 MCQs) from Micturition & Role of Other Organs in Excretion of Chapter 19: Excretory Products and Their Elimination (Class 11 NCERT + NEET UG level).

Part 6: Micturition & Role of Other Organs in Excretion

Q1. The process of expelling urine from the bladder is called:

a) Osmoregulation
b) Micturition
c) Ultrafiltration
d) Secretion

Answer: b) Micturition

Explanation:

• (a) Osmoregulation – water balance.
• ✅ (b) Micturition = urination.
• (c) Ultrafiltration – in glomerulus.
• (d) Secretion – in nephron tubules.

Q2. The micturition reflex is initiated by:

a) Stretch receptors in urinary bladder
b) Pressure in urethra
c) Pressure in kidney
d) Osmotic pressure of blood

Answer: a) Stretch receptors in urinary bladder

Explanation:

• ✅ (a) Stretch receptors → signal CNS → bladder contraction.
• (b) Urethral pressure not primary.
• (c) Kidney pressure – unrelated.
• (d) Osmotic pressure – role in ADH, not urination.

Q3. Which part of brain coordinates voluntary control of micturition?

a) Hypothalamus
b) Medulla oblongata
c) Cerebral cortex
d) Cerebellum

Answer: c) Cerebral cortex

Explanation:

• (a) Hypothalamus – hormone control.
• (b) Medulla – involuntary reflex.
• ✅ (c) Cerebral cortex – voluntary control over external sphincter.
• (d) Cerebellum – coordination, not urination.

Q4. Which sphincter is under voluntary control during urination?

a) Internal urethral sphincter
b) External urethral sphincter
c) Both
d) None

Answer: b) External urethral sphincter

Explanation:

• (a) Internal sphincter – involuntary (smooth muscle).
• ✅ (b) External sphincter – voluntary (skeletal muscle).
• (c) Not both.
• (d) Wrong.

Q5. Normal adult human urinary bladder capacity is about:

a) 50–100 ml
b) 200–300 ml
c) 400–600 ml
d) 1000 ml

Answer: c) 400–600 ml

Explanation:

• (a), (b) – too low.
• ✅ (c) Bladder holds ~400–600 ml before urge.
• (d) 1000 ml – abnormal distension.

Q6. Micturition reflex is mainly controlled by:

a) Spinal cord
b) Cerebral cortex
c) Cerebellum
d) Midbrain

Answer: a) Spinal cord

Explanation:

• ✅ (a) Spinal cord reflex center controls involuntary micturition.
• (b) Cortex – voluntary.
• (c), (d) – not major.

Q7. Which organ also excretes nitrogenous wastes besides kidneys?

a) Lungs
b) Liver
c) Skin
d) Both b and c

Answer: d) Both b and c

Explanation:

• (a) Lungs – CO₂, not nitrogen.
• ✅ (b) Liver – ammonia converted to urea.
• ✅ (c) Skin – sweat contains small urea.
• (d) Correct.

Q8. Which organ eliminates CO₂ and water?

a) Kidneys
b) Lungs
c) Liver
d) Skin

Answer: b) Lungs

Explanation:

• (a) Kidneys – urea, salts.
• ✅ (b) Lungs – excrete CO₂ & water vapor.
• (c) Liver – metabolic waste, bile.
• (d) Skin – sweat.

Q9. Which of the following is NOT an excretory organ?

a) Liver
b) Lungs
c) Spleen
d) Skin

Answer: c) Spleen

Explanation:

• (a) Liver – excretes bile pigments, urea formation.
• (b) Lungs – excrete CO₂.
• (c) ✅ Spleen – blood reservoir, not excretory.
• (d) Skin – sweat excretion.

Q10. Sweat contains:

a) Only water
b) Water and NaCl
c) Water, NaCl, and urea
d) Only urea

Answer: c) Water, NaCl, and urea

Explanation:

• (a), (b) – incomplete.
• ✅ (c) Sweat contains water, salts, small urea & lactic acid.
• (d) Wrong.

Q11. Which pigment is excreted in bile?

a) Bilirubin and biliverdin
b) Melanin
c) Hemoglobin
d) Myoglobin

Answer: a) Bilirubin and biliverdin

Explanation:

• ✅ (a) Bile pigments from hemoglobin breakdown.
• (b) Melanin – skin pigment.
• (c) Hemoglobin – oxygen carrier, not excreted.
• (d) Myoglobin – muscle protein.

Q12. The skin excretes waste through:

a) Sebaceous glands
b) Sweat glands
c) Both
d) None

Answer: b) Sweat glands

Explanation:

• (a) Sebaceous – oil secretion, not excretion.
• ✅ (b) Sweat glands – excrete salts, urea, water.
• (c) Not both.
• (d) Wrong.

Q13. Which waste is excreted by the liver into bile?

a) Uric acid
b) Bilirubin
c) Ammonia
d) Creatinine

Answer: b) Bilirubin

Explanation:

• (a) Uric acid – kidneys.
• ✅ (b) Bilirubin – excreted in bile.
• (c) Ammonia – converted to urea in liver.
• (d) Creatinine – kidney.

Q14. Which is the main excretory product of skin?

a) Urea
b) NaCl
c) Ammonia
d) Uric acid

Answer: b) NaCl

Explanation:

• (a) Urea – present in small amounts.
• ✅ (b) NaCl + water – major.
• (c), (d) – negligible.

Q15. Which organ converts ammonia into urea?

a) Kidney
b) Liver
c) Pancreas
d) Lungs

Answer: b) Liver

Explanation:

• (a) Kidney – excretes urea, not produces.
• ✅ (b) Liver – urea cycle converts ammonia → urea.
• (c) Pancreas – digestive enzymes.
• (d) Lungs – CO₂.

Q16. Which excretory organ regulates body temperature?

a) Kidney
b) Lungs
c) Skin
d) Liver

Answer: c) Skin

Explanation:

• (a) Kidney – osmoregulation.
• (b) Lungs – CO₂.
• ✅ (c) Skin → sweat evaporates → cooling.
• (d) Liver – metabolism.

Q17. Urination is under:

a) Involuntary control only
b) Voluntary control only
c) Both voluntary and involuntary control
d) Reflex action only

Answer: c) Both voluntary and involuntary control

Explanation:

• ✅ (c) Spinal reflex (involuntary) + cortex (voluntary sphincter).

Q18. The term for painful urination is:

a) Dysuria
b) Polyuria
c) Oliguria
d) Anuria

Answer: a) Dysuria

Explanation:

• ✅ (a) Dysuria – painful urination.
• (b) Polyuria – excessive urination.
• (c) Oliguria – reduced urine.
• (d) Anuria – absence of urine.

Q19. Which organ helps excrete cholesterol?

a) Liver
b) Kidney
c) Lungs
d) Skin

Answer: a) Liver

Explanation:

• ✅ (a) Cholesterol excreted via bile salts.

Q20. Which organ excretes lactic acid during sweating?

a) Kidney
b) Liver
c) Skin
d) Lungs

Answer: c) Skin

Explanation:

• ✅ (c) Sweat glands remove lactic acid.

Q21. Which is the main excretory organ for drug metabolism?

a) Kidney
b) Liver
c) Lungs
d) Skin

Answer: b) Liver

Explanation:

• ✅ (b) Liver metabolizes drugs → excreted in bile/urine.

Q22. During jaundice, which pigment accumulates in blood?

a) Uric acid
b) Creatinine
c) Bilirubin
d) Ammonia

Answer: c) Bilirubin

Explanation:

• ✅ (c) Excess bilirubin causes yellow skin/eyes.

Q23. Which organ primarily excretes volatile wastes?

a) Lungs
b) Liver
c) Kidney
d) Skin

Answer: a) Lungs

Explanation:

• ✅ (a) Lungs excrete CO₂ (volatile).

Q24. The reflex of micturition involves:

a) Parasympathetic nerves
b) Sympathetic nerves
c) Somatic motor nerves only
d) None

Answer: a) Parasympathetic nerves

Explanation:

• ✅ (a) Parasympathetic activation → bladder contraction.

Q25. Which organ plays a role in detoxification and excretion of toxins?

a) Kidney
b) Liver
c) Skin
d) Lungs

Answer: b) Liver

Explanation:

• ✅ (b) Liver detoxifies drugs, toxins, alcohol.

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