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Excretory products and elimination: NEET MCQs with answers

147 questions on this topic of Human Physiology (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.

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easy

1. Which segment of the human nephron is capable of conditional reabsorption of Na⁺ and water under hormonal control?

  1. Distal Convoluted Tubule (DCT)
  2. Descending limb of loop of Henle
  3. Proximal Convoluted Tubule (PCT)
  4. Thin ascending limb of loop of Henle
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Answer: (A) Distal Convoluted Tubule (DCT)

Conditional reabsorption of Na⁺ and water takes place in the Distal Convoluted Tubule (DCT). This process is regulated by hormones such as aldosterone and ADH to maintain electrolyte and fluid balance.

medium

2. Match Column-I with Column-II. Column-I: (A) Protonephridia (B) Nephridia (C) Malpighian tubules (D) Antennal glands Column-II: (i) Cockroach (ii) Prawn (iii) Planaria (iv) Earthworm

  1. A-(iv), B-(iii), C-(i), D-(ii)
  2. A-(iii), B-(iv), C-(i), D-(ii)
  3. A-(iii), B-(i), C-(iv), D-(ii)
  4. A-(ii), B-(iv), C-(i), D-(iii)
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Answer: (B) A-(iii), B-(iv), C-(i), D-(ii)

Planaria has protonephridia (flame cells), earthworm has nephridia, cockroach has Malpighian tubules and prawn has antennal (green) glands.

hard

3. How many of the following organisms excrete nitrogenous wastes mainly as uric acid? Pigeon, Lizard, Frog (adult), Cockroach, Land snail, Human, Bony fish

  1. Two
  2. Three
  3. Five
  4. Four
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Answer: (D) Four

Birds (pigeon), reptiles (lizard), insects (cockroach) and land snails are uricotelic. Adult frogs and humans are ureotelic, and bony fishes are ammonotelic.

medium

4. Urine formation involves three main processes. Which of the following is NOT one of them?

  1. Reabsorption
  2. Glomerular filtration
  3. Micturition
  4. Secretion
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Answer: (C) Micturition

Urine forms by glomerular filtration, reabsorption and secretion; micturition is the release of urine from the bladder.

easy

5. The juxtaglomerular apparatus (JGA) is a specialized sensitive region formed by cellular modifications in which specific regions of the nephron and its vasculature?

  1. Proximal convoluted tubule and afferent arteriole at the location of their contact
  2. Collecting duct and peritubular capillary network
  3. Loop of Henle and efferent arteriole at the location of their contact
  4. Distal convoluted tubule and afferent arteriole at the location of their contact
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Answer: (D) Distal convoluted tubule and afferent arteriole at the location of their contact

JGA is a special sensitive region formed by cellular modifications in the distal convoluted tubule (DCT) and the afferent arteriole at the location of their contact. A fall in GFR activates JG cells to release renin.

hard

6. The counter-current mechanism in the kidney operates between:

  1. The PCT and DCT
  2. Henle's loop and the vasa recta
  3. Bowman's capsule and the glomerulus
  4. The ureter and the urinary bladder
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Answer: (B) Henle's loop and the vasa recta

Flow in the two limbs of Henle's loop and the two limbs of the vasa recta is in opposite directions, forming the counter-current mechanism that maintains the medullary gradient.

medium

7. The mechanism involving renin, angiotensin and aldosterone that regulates kidney function is generally known as the:

  1. Hypophyseal portal system
  2. Counter-current mechanism
  3. Micturition reflex
  4. Renin–angiotensin mechanism
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Answer: (D) Renin–angiotensin mechanism

This regulatory cascade is called the renin–angiotensin mechanism.

medium

8. Nearly all essential nutrients and 70-80 per cent of electrolytes and water are reabsorbed in the:

  1. Ascending limb of Henle's loop
  2. Distal convoluted tubule
  3. Proximal convoluted tubule
  4. Collecting duct
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Answer: (C) Proximal convoluted tubule

The PCT is lined by simple cuboidal brush-border epithelium that increases the surface area for reabsorption. It also helps maintain pH and ionic balance by selective secretion of H+, ammonia and K+.

NCERT Class 11

easy

9. Which of the following pairs of excretory organs and organisms is correctly matched according to NCERT?

  1. Nephridia - Earthworm
  2. Antennal glands - Planaria
  3. Protonephridia - Prawn
  4. Malpighian tubules - Amphioxus
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Answer: (A) Nephridia - Earthworm

Earthworms and other annelids possess nephridia as their excretory and osmoregulatory organs. Protonephridia or flame cells are found in flatworms (Planaria) and Amphioxus, while antennal or green glands are excretory structures in crustaceans like prawns.

medium

10. Given below are two statements: Statement I: Angiotensin II is a powerful vasoconstrictor that increases glomerular blood pressure and thereby GFR. Statement II: Angiotensin II also activates the adrenal medulla to release aldosterone. In light of the above statements, choose the correct answer:

  1. Both Statement I and Statement II are correct
  2. Statement I is correct but Statement II is incorrect
  3. Statement I is incorrect but Statement II is correct
  4. Both Statement I and Statement II are incorrect
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Answer: (B) Statement I is correct but Statement II is incorrect

Angiotensin II is indeed a powerful vasoconstrictor that increases glomerular blood pressure and GFR (Statement I is correct). However, Angiotensin II activates the adrenal cortex (not adrenal medulla) to release aldosterone (Statement II is incorrect).

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11. Each human kidney has nearly how many nephrons?

  1. Ten million
  2. One thousand
  3. One million
  4. One hundred thousand
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Answer: (C) One million

Each kidney has nearly one million complex tubular structures called nephrons, the functional units.

hard

12. Given below are two statements. Statement I: ADH secretion decreases when the body loses a large amount of fluid. Statement II: An excessive intake of water switches off the osmoreceptors and suppresses ADH release. Choose the correct answer.

  1. Both Statement I and Statement II are correct
  2. Statement I is correct but Statement II is incorrect
  3. Statement I is incorrect but Statement II is correct
  4. Both Statement I and Statement II are incorrect
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Answer: (C) Statement I is incorrect but Statement II is correct

Fluid loss increases ADH release to conserve water. Excess fluid intake switches off osmoreceptors and suppresses ADH, completing the feedback.

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