Excretory System - Competency-Based Question Bank (with Answers)

Section A: Case-Based Questions

Case Study 1: Person in desert with limited water, concentrated yellow urine.

1. Identify the hormone.
   • Answer: ADH (Anti-Diuretic Hormone) or Vasopressin.
2. Target site of the hormone.
   • Answer: Distal Convoluted Tubule (DCT) and Collecting Duct.
3. Designing: Predict change after drinking water.
   • Answer: Urine will become dilute (hypotonic) and large in volume as ADH secretion decreases.
4. Analysis: Osmoregulation.
   • Answer: The process of maintaining the constant osmotic pressure/water-salt balance of the blood.
5. Why yellow?
   • Answer: Presence of Urochrome, a pigment formed from the breakdown of hemoglobin.

Case Study 2: Patient undergoing Haemodialysis. 6. Principle of dialysis.

• Answer: Diffusion/Osmosis across a semi-permeable (cellophane) membrane.

7. Why compose fluid like plasma without waste?
   • Answer: To create a concentration gradient so nitrogenous wastes (Urea) move from blood to fluid, while essential nutrients remain in the blood.
8. Creating: Dialysis diagram.
   • Answer: [Description: Blood pumped from artery through tubes in a tank of dialysing fluid, then returned to a vein].
9. Critical Thinking: Why not a permanent cure?
   • Answer: It only filters waste; it cannot perform other kidney functions like hormone production (Erythropoietin) or active regulation. Kidney transplant is the permanent solution.
10. Survive with one kidney?
    • Answer: Yes. The remaining kidney undergoes compensatory hypertrophy (increases in size and function) to handle the load.

Section B: Assertion-Reasoning Questions

Directions: (a) Both A/R true, R explains A; (b) Both true, R doesn't explain A; (c) A true, R false; (d) A false, R true.

11. Assertion (A): Efferent arteriole is narrower than afferent. Reason (R): Creates high hydrostatic pressure for ultrafiltration.
    • Answer: (a) Both A and R are true and R is the correct explanation.
12. Assertion (A): Glucose is not in normal urine. Reason (R): It is completely reabsorbed in PCT.
    • Answer: (a) Both A and R are true and R is the correct explanation.
13. Assertion (A): Urine is slightly acidic. Reason (R): Secretion of H+ ions into filtrate.
    • Answer: (a) Both A and R are true and R is the correct explanation.
14. Assertion (A): Liver is an excretory organ. Reason (R): It produces urea.
    • Answer: (a) Both A and R are true and R is the correct explanation.
15. Assertion (A): Alcohol leads to frequent urination. Reason (R): Alcohol inhibits ADH.
    • Answer: (a) Both A and R are true and R is the correct explanation.

Section C: Creating and Designing (Application & Analysis)

16. Designing: Steps of urine formation flowchart.
    • Answer: Glomerulus (Ultrafiltration) -> PCT/Henle/DCT (Selective Reabsorption) -> DCT/Collecting Duct (Tubular Secretion) -> Urine.
17. Creating: Nephron Map.
    • Answer: [PCT: Glucose, Amino acids, 65% water. Loop of Henle: Water (descending), Salts (ascending). DCT: Salts and Water (facultative)].
18. Analysis: Filtrate vs Urine.
    • Answer: Filtrate contains glucose/amino acids; urine does not. Proteins are absent in both because they are too large to pass the glomerular filter.
19. Designing: Table of waste products.
    • Answer: [Urea: Protein metabolism. Uric acid: Nucleic acid metabolism. Creatinine: Muscle metabolism].
20. Visualisation: Malpighian Body diagram.
    • Answer: [Description: Cup-like Bowman's capsule surrounding a tuft of capillaries].
21. Application: Drink water in summer.
    • Answer: To compensate for water lost through sweating (thermoregulation) and prevent dehydration/concentrated urine.
22. Creating: Glomerulus mimic.
    • Answer: A high-pressure pump pushing liquid through an ultra-fine mesh filter.
23. Analysis: Threshold Substance.
    • Answer: A substance reabsorbed efficiently by the kidney. Glucose is "high-threshold" because it's only excreted if its blood level exceeds a certain limit (Renal threshold).
24. Designing: Kidney stone diet.
    • Answer: Avoid spinach, tomatoes, and nuts (high in oxalates). Increase water intake.
25. Creating: Kidney-Brain dialogue.
    • Answer: Kidney: "Hey Brain, the blood is too salty!" Brain: "Copy that, releasing ADH now. Hold onto that water!"

Section D: Competency & Critical Thinking

26. Ultrafiltration.
    • Answer: Filtration under high pressure where almost all liquid components (except proteins/cells) are forced out.
27. Scenario: Blood in urine (Haematuria).
    • Answer: Possible kidney stone or infection causing damage to the urinary tract lining.
28. Critical Thinking: Ammonia vs Urea.
    • Answer: Ammonia is highly toxic and needs lots of water to flush; suitable for fish. Urea is less toxic and conserves water; suitable for land mammals.
29. Application: Gout.
    • Answer: Inflammation of joints due to accumulation of Uric acid crystals.
30. Excretion vs Egestion.
    • Answer: Excretion: Removal of metabolic waste from cells. Egestion: Removal of undigested food from the gut.
31. Diagram Based: Urinary system.
    • Answer: Sphincter muscles control the release of urine from the bladder (voluntary control).
32. Skin in excretion.
    • Answer: Sweat glands remove water, salts, and small amounts of urea.
33. Analysis: Right kidney lower.
    • Answer: Due to the large space occupied by the liver on the right side.
34. Competency: Counter-current mechanism.
    • Answer: The flow of filtrate in opposite directions in the two limbs of the Loop of Henle helps build an osmotic gradient in the medulla to concentrate urine.
35. Case: High protein effect.
    • Answer: More protein -> More deamination in liver -> More Urea in blood -> More Urea in urine.
36. Creating: Caffeine hypothesis.
    • Answer: Caffeine increases blood flow to kidneys and inhibits ADH, increasing urine output.
37. Designing: Deamination visual.
    • Answer: Amino Acid -> Ammonia ($NH_3$) -> Ornithine Cycle -> Urea.
38. Application: pH maintenance.
    • Answer: Kidneys secrete H+ ions and reabsorb $HCO_3^-$ ions to keep blood pH constant (approx 7.4).
39. Critical Thinking: Is urine sterile?
    • Answer: Yes, inside a healthy bladder, but it picks up bacteria as it exits the body.
40. Analysis: Micturition.
    • Answer: The act of passing urine. It is a reflex initiated by stretch receptors, but controllable by the brain.

Section E: Advanced Competency

41. Scenario: Diabetes Insipidus.
    • Answer: Deficiency of ADH. Different from Mellitus (Insulin deficiency/Sugar). "Insipidus" means tasteless urine.
42. Designing: Model.
    • Answer: Funnel (Capsule), Plastic tube (Nephron), Bottle (Bladder).
43. Application: Shivering while urinating in cold.
    • Answer: Emptying a warm bladder causes a sudden drop in core temperature; shivering generates heat to compensate.
44. Creating: Crossword.
    • Answer: [Terms: Cortex (Outer), Medulla (Inner), Hilum (Notch)].
45. Case Study: Hydronephrosis.
    • Answer: Back-pressure of urine causes the kidney to swell and tissue to atrophy.
46. JGA role.
    • Answer: Detects low BP and releases Renin, which leads to vasoconstriction and salt/water retention to raise BP.
47. Critical Thinking: Longer Loop of Henle.
    • Answer: Allows for greater water reabsorption, producing highly concentrated urine for water conservation.
48. Analysis: Cortical vs Juxtamedullary.
    • Answer: Cortical: Loop of Henle is short. Juxtamedullary: Loop of Henle is long and deep in medulla (for concentrating urine).
49. Designing: Urea concentration graph.
    • Answer: High in Renal Artery, significantly lower in Renal Vein.
50. Creating: Smart Toilet parameters.
    • Answer: Protein (Kidney health), Glucose (Diabetes), pH, Specific Gravity (Hydration).