Excretory Answers
ANSWER KEY
1. D
11. B
2. C
12. D
3. B
13. B
4. A
14. A
5. C
15. D
6. D
16. C
7. A
17. A
8. C
18. D
9. A
19. C
10. C
20. B
21. B
22. C
23. C
24. C
25. B
26. A
27. A
28. D
29. D
30. D
31. C
32. A
33. A
34. B
35. B
36. D
37. A
38. B
39. C
40. B
41. C
42. D
43. A
44. C
45. B
46. D
47. A
48. A
49. A
50. B
51. D
52. A
53. B
54. B
55. C
56. D
57. D
58. C
59. A
60. D
61. B
62. A
63. D
64. A
65. D
66. C
67. D
68. C
69. A
70. A
71. W: afferent arteriole • Brings blood to the glomerulus.
X: proximal tubule • Reabsorbs water.• Selectively reabsorbs nutrients such as glucose and amino acids.
Y: distal convoluted tubule • Reabsorbs water. • Regulates blood pH.• Carries out selective reabsorption of K, H+,
NaCl and HCO3Z: loop of Henle : • Osmoregulation. • Maintains salt and water balance.
72. W: renal cortex X: renal pelvis Y: ureter Z: bladder (1 mark)
73. • excretion of penicillin in distal convoluted tubule
• excretion of histamines in distal convoluted tubule
• excretion of hydrogen ions in distal convoluted tubule
• excretion of uric acid at the distal convoluted tubule
• excretion of creatinine at the distal convoluted tubule
• excretion of ammonia at the distal convoluted tubule
• re-absorption of glucose in proximal convoluted tubule
74. Proximal Tubule:
• Selective reabsorption.
• Glucose is actively transported into the blood.
• Fatty acids and glycerol are actively transported into
the blood.
• Water is reabsorbed passively by osmosis.
• Na+ ions are actively transported into the blood.
• Cl- ions are passively reabsorbed by the blood.
any two for 1 mark each
75. Path One:
• Stretch receptors in the walls of the
arteries detect that the plasma lacks
sufficient water.
• ADH produced by hypothalamic
neurons is transported to the
posterior pituitary where it is
released into the blood.
• ADH increases the permeability of
the distal convoluted tubule and the
collecting duct in the nephron.
• This increased permeability causes
more water to be reabsorbed.
• re-absorption of sodium ions in proximal convoluted
tubule
• re-absorption of amino acids in proximal convoluted
tubule
• active transport of sodium ions into medulla in loop of
Henle
any four for 1 mark each
Loop of Henle:
• Counter-current exchange.
• Na+ ions are transported out of the ascending limbs
by active transport ( Cl– follows passively).
• There is increasing salt concentration in the medulla.
• The tissue surrounding the descending limbs is saltier
and H2O is drawn out of the nephron.
any two for 1 mark each
• Increased H2O in the plasma will
return ion concentrations to normal
levels.
• As the blood becomes more dilute,
ADH ceases to be produced and
released.
• This mechanism is an example of
negative feedback.
Path Two:
• Osmoreceptors in the
hypothalamus detect that the plasma
lacks sufficient water.
• The hypothalamus causes
sensations of thirst.
• The student drinks.
• Water is absorbed from the
stomach, small intestine and large
intestine into the blood.
• Blood volume is increased.
Path Three:
• Kidney releases an enzyme when
blood volume and Na+ is low which
eventually targets adrenal gland.
• Adrenal gland releases
aldosterone.
• Aldosterone targets kidney tubules.
• This increases Na+ recovery in the
nephrons.
• This results in increased water
recovery and subsequent increase in
blood volume.
(Students may describe a
combination of pathway