1. The primary excretory organ in humans is ____________.
A) Liver
B) Kidney
C) Lungs
D) Skin
Answer: B
Explanation: Kidneys filter blood and remove nitrogenous wastes (mainly urea).
2. How many kidneys are present in humans?
A) One
B) Two
C) Three
D) Four
Answer: B
Explanation: Humans normally have two kidneys located in the abdominal cavity.
3. The structural and functional unit of the kidney is:
A) Nephron
B) Glomerulus
C) Bowman’s capsule
D) Loop of Henle
Answer: A
Explanation: Each kidney has about 1–1.5 million nephrons that filter blood.
4. The functional unit of kidney was discovered by____________.
A) William Harvey
B) Malpighi
C) Bowman
D) Henle
Answer: B
Explanation: Marcello Malpighi discovered nephrons, the filtration units of kidney.
5. What is the normal length of a human kidney?
A) 2–3 cm
B) 5–6 cm
C) 10–12 cm
D) 15–20 cm
Answer: C
Explanation: Each kidney is bean-shaped, about 10–12 cm long.
6. Which part of the nephron filters blood?
A) Henle’s loop
B) Bowman’s capsule
C) Distal tubule
D) Collecting duct
Answer: B
Explanation: Bowman’s capsule encloses the glomerulus, where filtration occurs.
7. Which artery supplies blood to the kidneys?
A) Coronary artery
B) Pulmonary artery
C) Renal artery
D) Hepatic artery
Answer: C
Explanation: The renal artery branches from the aorta and supplies blood to kidneys.
8. Which vein carries blood away from the kidneys?
A) Pulmonary vein
B) Renal vein
C) Jugular vein
D) Hepatic vein
Answer: B
Explanation: The renal vein carries purified blood back to the inferior vena cava.
9. What is the outer layer of the kidney called?
A) Cortex
B) Medulla
C) Pelvis
D) Capsule
Answer: A
Explanation: The kidney has an outer cortex and an inner medulla.
10. Which structure connects the kidney to the urinary bladder?
A) Urethra
B) Ureter
C) Nephron
D) Glomerulus
Answer: B
Explanation: Each kidney has a ureter that carries urine to the bladder.
11. The tube that carries urine out of the body is____________.
A) Ureter
B) Urethra
C) Bowman’s capsule
D) Nephron
Answer: B
Explanation: The urethra opens to the outside for urine excretion.
12. Which organ stores urine temporarily?
A) Kidney
B) Ureter
C) Urinary bladder
D) Urethra
Answer: C
Explanation: The bladder is a muscular sac that stores urine.
13. The process of urine release is called____________.
A) Egestion
B) Micturition
C) Filtration
D) Absorption
Answer: B
Explanation: Micturition is the act of passing urine out of the body.
14. How much blood is filtered by both kidneys in 24 hours?
A) 50 liters
B) 100 liters
C) 170 liters
D) 500 liters
Answer: C
Explanation: About 170 liters of blood plasma is filtered daily, producing ~1.5 liters urine.
15. The nitrogenous waste in humans is mainly____________.
A) Ammonia
B) Urea
C) Uric acid
D) Creatinine
Answer: B
Explanation: Humans are ureotelic; they excrete nitrogen mainly as urea.
16. Urea is synthesized in which organ?
A) Kidney
B) Liver
C) Spleen
D) Pancreas
Answer: B
Explanation: Urea is produced in the liver through the ornithine cycle.
17. Which organ is called the “chemical factory” of the body?
A) Heart
B) Kidney
C) Liver
D) Brain
Answer: C
Explanation: The liver synthesizes proteins, detoxifies, and forms urea.
18. Which part of nephron reabsorbs water?
A) Bowman’s capsule
B) Henle’s loop
C) Distal tubule
D) Collecting duct
Answer: B
Explanation: Henle’s loop is key in water reabsorption and urine concentration.
19. Which hormone controls water balance in the body?
A) Insulin
B) ADH
C) Thyroxine
D) Cortisol
Answer: B
Explanation: Antidiuretic hormone (vasopressin) regulates water reabsorption in kidneys.
20. Deficiency of ADH causes____________.
A) Diabetes mellitus
B) Diabetes insipidus
C) Jaundice
D) Hypertension
Answer: B
Explanation: Lack of ADH leads to excessive urine output (polyuria).
21. Which pigment gives yellow color to urine?
A) Hemoglobin
B) Bilirubin
C) Urochrome
D) Melanin
Answer: C
Explanation: Urochrome (from hemoglobin breakdown) gives yellow urine color.
22. Which organ removes CO₂ from the body?
A) Kidneys
B) Liver
C) Lungs
D) Skin
Answer: C
Explanation: Lungs excrete CO₂ and water vapor during respiration.
23. Which organ removes excess salts and water via sweat?
A) Liver
B) Lungs
C) Skin
D) Intestine
Answer: C
Explanation: Sweat glands excrete water, salts, and small amounts of urea.
24. Which vitamin deficiency leads to kidney stone formation?
A) Vitamin A
B) Vitamin B12
C) Vitamin C
D) Vitamin D
Answer: A
Explanation: Vitamin A deficiency causes epithelial damage, predisposing to kidney stones.
25. What is the normal pH of human urine?
A) 4.0–5.0
B) 5.5–7.0
C) 7.5–8.0
D) 9.0–10.0
Answer: B
Explanation: Urine is slightly acidic, pH varies with diet.
26. Each nephron begins with____________.
A) Loop of Henle
B) Collecting duct
C) Bowman’s capsule
D) Distal tubule
Answer: C
Explanation: Bowman’s capsule surrounds the glomerulus and performs ultrafiltration.
27. The tuft of capillaries inside Bowman’s capsule is called____________.
A) Loop of Henle
B) Glomerulus
C) Vasa recta
D) Collecting duct
Answer: B
Explanation: Glomerulus is a network of capillaries where blood filtration starts.
28. The process of filtration in Bowman’s capsule is called____________.
A) Tubular secretion
B) Ultrafiltration
C) Active transport
D) Exocytosis
Answer: B
Explanation: Blood pressure forces small molecules (urea, glucose, salts, water) into Bowman’s capsule.
29. Which substances are normally reabsorbed in the proximal tubule?
A) Urea and uric acid
B) Glucose, amino acids, salts, water
C) Only urea
D) Only water
Answer: B
Explanation: The proximal tubule reabsorbs most nutrients and water into the blood.
30. Which part of nephron is mainly responsible for urine concentration?
A) Proximal tubule
B) Loop of Henle
C) Distal tubule
D) Bowman’s capsule
Answer: B
Explanation: Loop of Henle creates a concentration gradient to reabsorb water and salts.
31. Which blood vessels surround the nephron tubules for exchange?
A) Coronary vessels
B) Pulmonary vessels
C) Peritubular capillaries
D) Jugular vein
Answer: C
Explanation: These capillaries reabsorb useful substances from nephron tubules.
32. Which structure connects several nephrons before urine reaches the ureter?
A) Loop of Henle
B) Collecting duct
C) Proximal tubule
D) Distal tubule
Answer: B
Explanation: The collecting duct receives urine from multiple nephrons and delivers it to renal pelvis.
33. Which process helps in selective reabsorption?
A) Diffusion and osmosis
B) Active transport
C) Passive transport
D) All of the above
Answer: D
Explanation: Selective reabsorption involves diffusion, osmosis, and active transport mechanisms.
34. Which hormone increases water reabsorption in the collecting duct?
A) Insulin
B) ADH (Vasopressin)
C) Aldosterone
D) Cortisol
Answer: B
Explanation: ADH makes collecting duct walls permeable to water, concentrating urine.
35. Aldosterone hormone primarily increases reabsorption of____________.
A) Calcium
B) Sodium
C) Potassium
D) Urea
Answer: B
Explanation: Aldosterone (from adrenal cortex) increases sodium reabsorption and potassium excretion.
36. Which part of the nephron is affected in diabetes insipidus?
A) Loop of Henle
B) Collecting duct
C) Bowman’s capsule
D) Proximal tubule
Answer: B
Explanation: Without ADH, the collecting duct cannot reabsorb water → dilute, excessive urine.
37. Which part of nephron is highly coiled and lies close to Bowman’s capsule?
A) Loop of Henle
B) Proximal convoluted tubule (PCT)
C) Distal convoluted tubule (DCT)
D) Collecting duct
Answer: B
Explanation: PCT reabsorbs ~70% of filtered water, salts, and nutrients.
38. The U-shaped part of nephron is____________.
A) Collecting duct
B) Distal tubule
C) Loop of Henle
D) Glomerulus
Answer: C
Explanation: Loop of Henle is U-shaped and plays a key role in urine concentration.
39. In which part of nephron does secretion of hydrogen ions and potassium ions occur?
A) PCT
B) Loop of Henle
C) DCT
D) Bowman’s capsule
Answer: C
Explanation: The distal convoluted tubule secretes H⁺ and K⁺ to maintain pH and ionic balance.
40. Which structure collects urine from the collecting ducts?
A) Renal pelvis
B) Ureter
C) Renal vein
D) Medulla
Answer: A
Explanation: Urine from collecting ducts drains into renal pelvis before ureter.
41. Which substance should NOT normally be present in urine?
A) Urea
B) Glucose
C) Salts
D) Water
Answer: B
Explanation: Presence of glucose in urine (glycosuria) indicates diabetes mellitus.
42. Presence of excess protein in urine is called____________.
A) Glycosuria
B) Albuminuria
C) Hematuria
D) Pyuria
Answer: B
Explanation: Albuminuria indicates kidney damage (nephritis).
43. Blood in urine is known as____________.
A) Glycosuria
B) Pyuria
C) Hematuria
D) Albuminuria
Answer: C
Explanation: Hematuria occurs due to infections, stones, or trauma to urinary tract.
44. Pus cells in urine indicate____________.
A) Diabetes mellitus
B) Kidney stone
C) Urinary tract infection
D) Jaundice
Answer: C
Explanation: Pyuria (pus in urine) is caused by UTI.
45. Which waste is excreted in the smallest amount in urine?
A) Urea
B) Uric acid
C) Creatinine
D) Ammonia
Answer: D
Explanation: Ammonia is converted to urea in liver, so its excretion is minimal.
46. The counter-current mechanism in nephron is associated with____________.
A) Bowman’s capsule
B) Loop of Henle
C) Distal tubule
D) Renal pelvis
Answer: B
Explanation: Counter-current exchange in Henle’s loop helps concentrate urine.
47. Creatinine in urine is a result of metabolism of____________.
A) Proteins
B) Carbohydrates
C) Creatine in muscles
D) Fats
Answer: C
Explanation: Creatinine is a byproduct of creatine metabolism in muscles, excreted in urine.
48. Normal daily urine output in adults is____________.
A) 200–300 ml
B) 500–800 ml
C) 1–1.5 liters
D) 3–4 liters
Answer: C
Explanation: Average urine excretion is ~1–1.5 liters per day.
49. Which test is used to measure urea content in blood?
A) ECG
B) BUN test
C) MRI
D) X-ray
Answer: B
Explanation: BUN (Blood Urea Nitrogen) test measures kidney function.
50. In prolonged fasting, the major excretory product is____________.
A) Urea
B) Ketone bodies
C) Uric acid
D) Ammonia
Answer: B
Explanation: In fasting, fats are broken down producing ketone bodies, excreted in urine.
51. The presence of glucose in urine is called____________.
A) Hematuria
B) Glycosuria
C) Albuminuria
D) Pyuria
Answer: B
Explanation: Glycosuria occurs in diabetes mellitus due to high blood sugar.
52. Kidney stones are chemically often made of____________.
A) Sodium bicarbonate
B) Calcium oxalate
C) Potassium nitrate
D) Sodium chloride
Answer: B
Explanation: Kidney stones usually consist of calcium oxalate or uric acid crystals.
53. Which disease is caused by failure of kidneys to excrete waste?
A) Jaundice
B) Uremia
C) Diabetes insipidus
D) Tuberculosis
Answer: B
Explanation: In uremia, urea accumulates in blood due to kidney failure.
54. Which condition refers to inflammation of kidneys?
A) Nephritis
B) Nephrosis
C) Cystitis
D) Pyelitis
Answer: A
Explanation: Nephritis is kidney inflammation that impairs filtration.
55. The disease “Bright’s disease” is associated with____________.
A) Stomach
B) Kidney
C) Liver
D) Heart
Answer: B
Explanation: Bright’s disease is a form of nephritis affecting kidney function.
56. Which hormone deficiency causes diabetes insipidus?
A) Insulin
B) ADH
C) Aldosterone
D) Cortisol
Answer: B
Explanation: Lack of antidiuretic hormone (ADH) leads to excess dilute urine.
57. In diabetes insipidus, the urine is____________.
A) Sweet smelling
B) High in glucose
C) Dilute and tasteless
D) Acidic
Answer: C
Explanation: “Insipidus” means tasteless, because urine lacks sugar but is very dilute.
58. Which of the following is NOT an excretory disease?
A) Uremia
B) Nephritis
C) Hypertension
D) Kidney stones
Answer: C
Explanation: Hypertension is a cardiovascular disorder, not primarily excretory.
59. Dialysis is used in patients with____________.
A) Diabetes mellitus
B) Hypertension
C) Kidney failure
D) Asthma
Answer: C
Explanation: Dialysis removes waste from blood when kidneys fail.
60. The principle of dialysis is based on____________.
A) Active transport
B) Diffusion across semi-permeable membrane
C) Endocytosis
D) Exocytosis
Answer: B
Explanation: Dialysis uses diffusion to remove urea and toxins from blood.
61. Which waste product is mainly removed during dialysis?
A) Glucose
B) Urea
C) Hemoglobin
D) Proteins
Answer: B
Explanation: Dialysis eliminates urea and other nitrogenous wastes.
62. Hemodialysis is performed by diverting blood through a____________.
A) Kidney transplant
B) Dialysis machine
C) Heart-lung machine
D) Lymphatic filter
Answer: B
Explanation: In hemodialysis, patient’s blood passes through a dialysis machine for cleaning.
63. Which type of dialysis is done using the abdominal membrane?
A) Hemodialysis
B) Peritoneal dialysis
C) Artificial kidney dialysis
D) Plasma dialysis
Answer: B
Explanation: In peritoneal dialysis, the peritoneum acts as a natural filter.
64. A kidney transplant is usually placed in the____________.
A) Thoracic cavity
B) Lower abdomen
C) Upper back
D) Chest wall
Answer: B
Explanation: Transplanted kidneys are placed in the lower abdominal cavity.
65. The first successful human kidney transplant was performed in ____________.
A) 1954
B) 1965
C) 1978
D) 1985
Answer: A
Explanation: Joseph Murray performed the first successful kidney transplant in 1954.
66. Which blood group is considered a universal donor in transplants?
A) A
B) B
C) AB
D) O
Answer: D
Explanation: O group lacks A and B antigens, so it is universally compatible.
67. Which antigen causes kidney transplant rejection?
A) ABO antigens
B) MHC (HLA) antigens
C) Rh antigen
D) Albumin antigen
Answer: B
Explanation: Human leukocyte antigens (MHC) trigger transplant rejection.
68. Immunosuppressive drugs in transplants are used to____________.
A) Increase kidney function
B) Reduce urine output
C) Prevent organ rejection
D) Increase antibody production
Answer: C
Explanation: Drugs like cyclosporine suppress immunity to avoid graft rejection.
69. Which condition causes painful urination?
A) Pyelonephritis
B) Cystitis
C) Urethritis
D) All of the above
Answer: D
Explanation: Infections of urinary tract (bladder, kidney, urethra) cause painful urination.
70. “Renal calculi” refers to____________.
A) Kidney swelling
B) Kidney stones
C) Kidney infection
D) Kidney failure
Answer: B
Explanation: Renal calculi are mineral stones formed inside kidneys.
71. Which test is commonly used to detect kidney function?
A) Lipid profile
B) ECG
C) Serum creatinine test
D) Hemoglobin test
Answer: C
Explanation: Creatinine levels in blood indicate kidney efficiency.
72. Which condition may require immediate dialysis?
A) Low blood sugar
B) High blood pressure
C) High blood urea level
D) Low oxygen level
Answer: C
Explanation: Excessive urea accumulation in blood (uremia) requires dialysis.
73. The common symptom of kidney failure is____________.
A) High fever
B) Loss of vision
C) Edema (swelling)
D) Hair fall
Answer: C
Explanation: Fluid retention due to kidney failure causes swelling in feet and face.
74. The presence of excessive uric acid crystals in joints is called____________.
A) Arthritis
B) Gout
C) Nephritis
D) Anemia
Answer: B
Explanation: Gout occurs due to deposition of uric acid crystals in joints.
75. Which lifestyle habit is most harmful for kidney health?
A) Drinking water
B) Eating fruits
C) Smoking and alcohol
D) Light exercise
Answer: C
Explanation: Smoking and alcohol damage kidneys and worsen kidney diseases.
76. Which organ is sometimes called the “second kidney” because it also excretes waste?
A) Liver
B) Lungs
C) Skin
D) Spleen
Answer: A
Explanation: The liver detoxifies, produces urea, and removes toxins, hence called the second kidney.
77. Which of the following is NOT an excretory organ in humans?
A) Kidneys
B) Lungs
C) Skin
D) Pancreas
Answer: D
Explanation: Pancreas is digestive, not excretory. Kidneys, lungs, skin, and liver are excretory.
78. Which compound is the major nitrogenous waste in humans?
A) Ammonia
B) Uric acid
C) Urea
D) Creatinine
Answer: C
Explanation: Humans are ureotelic; urea is the main nitrogenous excretory product.
79. Ornithine cycle (urea cycle) occurs in the____________.
A) Kidney
B) Liver
C) Spleen
D) Heart
Answer: B
Explanation: Urea is synthesized in the liver by the ornithine cycle.
80. Which organ excretes bilirubin and bile pigments?
A) Kidney
B) Liver
C) Pancreas
D) Lungs
Answer: B
Explanation: The liver excretes bilirubin and bile salts into bile for elimination.
81. Which blood test indicates high urea levels?
A) CBC test
B) BUN test
C) Lipid profile
D) ESR test
Answer: B
Explanation: Blood Urea Nitrogen (BUN) measures urea concentration in blood.
82. Which condition is caused by reduced kidney filtration rate (GFR)?
A) Hypertension
B) Renal failure
C) Diabetes insipidus
D) Acidosis
Answer: B
Explanation: Decline in GFR results in waste accumulation and renal failure.
83. Normal Glomerular Filtration Rate (GFR) in adults is about____________.
A) 25 ml/min
B) 50 ml/min
C) 125 ml/min
D) 200 ml/min
Answer: C
Explanation: GFR is ~125 ml/min (180 liters/day), showing kidney efficiency.
84. Which ion’s balance is mainly regulated by aldosterone?
A) Sodium (Na⁺)
B) Calcium (Ca²⁺)
C) Chloride (Cl⁻)
D) Magnesium (Mg²⁺)
Answer: A
Explanation: Aldosterone increases sodium reabsorption and potassium excretion.
85. Which hormone increases calcium reabsorption by kidneys?
A) Calcitonin
B) Parathyroid hormone (PTH)
C) Insulin
D) Glucagon
Answer: B
Explanation: PTH promotes calcium reabsorption and reduces its loss in urine.
86. Which enzyme regulates blood pressure by kidney action?
A) Pepsin
B) Renin
C) Trypsin
D) Amylase
Answer: B
Explanation: Renin triggers renin-angiotensin mechanism to increase blood pressure.
87. Juxtaglomerular cells in kidney secrete____________.
A) ADH
B) Renin
C) Aldosterone
D) Erythropoietin
Answer: B
Explanation: JG cells secrete renin to regulate blood pressure and GFR.
88. Erythropoietin hormone produced by kidneys stimulates____________.
A) WBC production
B) RBC production
C) Platelet formation
D) Hemoglobin breakdown
Answer: B
Explanation: Erythropoietin stimulates bone marrow to produce more RBCs.
89. The presence of ketone bodies in urine indicates____________.
A) Diabetes mellitus
B) Kidney stones
C) UTI
D) Hypertension
Answer: A
Explanation: In diabetes, fat metabolism produces ketone bodies, appearing in urine (ketonuria).
90. Which disease is characterized by pus cells in urine?
A) Pyuria
B) Hematuria
C) Glycosuria
D) Albuminuria
Answer: A
Explanation: Pyuria occurs due to urinary tract infections.
91. Which vitamin prevents formation of kidney stones?
A) Vitamin A
B) Vitamin B1
C) Vitamin C
D) Vitamin K
Answer: A
Explanation: Vitamin A maintains epithelial health and prevents stone formation.
92. Which condition results from excessive uric acid in blood?
A) Anemia
B) Jaundice
C) Gout
D) Acidosis
Answer: C
Explanation: Gout causes deposition of uric acid crystals in joints.
93. Which part of nephron creates hyperosmotic medullary gradient?
A) Bowman’s capsule
B) Loop of Henle
C) Distal tubule
D) Collecting duct
Answer: B
Explanation: Counter-current mechanism in Loop of Henle maintains concentration gradient.
94. In prolonged fasting, the major nitrogenous waste is____________.
A) Urea
B) Uric acid
C) Ketone bodies
D) Creatinine
Answer: C
Explanation: Fasting increases fat metabolism, producing ketone bodies.
95. The kidneys are located at which vertebral level?
A) Thoracic T1–T5
B) Lumbar L1–L3
C) Sacral S1–S5
D) Cervical C1–C5
Answer: B
Explanation: Kidneys lie in the upper lumbar region on either side of the vertebral column.
96. The left kidney is positioned slightly____________.
A) Lower than right kidney
B) Higher than right kidney
C) Same level as right kidney
D) In front of right kidney
Answer: B
Explanation: Right kidney is lower due to the presence of the liver above it.
97. Which part of nephron regulates pH of blood?
A) Bowman’s capsule
B) Proximal tubule
C) Distal tubule
D) Loop of Henle
Answer: C
Explanation: DCT secretes H⁺ ions and reabsorbs bicarbonates, maintaining pH balance.
98. The kidney’s outer protective covering is____________.
A) Capsule
B) Cortex
C) Medulla
D) Pelvis
Answer: A
Explanation: A fibrous capsule surrounds and protects each kidney.
99. Which waste is excreted in maximum amount in urine?
A) Urea
B) Uric acid
C) Creatinine
D) Ammonia
Answer: A
Explanation: Urea (~2% of urine) is the principal nitrogenous waste excreted.
100. The process of removing kidney stones surgically is called ____________.
A) Lithotripsy
B) Nephrectomy
C) Dialysis
D) Transplant
Answer: A
Explanation: Lithotripsy uses shock waves to break kidney stones for removal.