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🟢 Easy Level (1–20)
- The main organ of the human excretory system is:
A) Liver
B) Kidney ✅
C) Lung
D) Heart
Explanation: Kidneys filter blood to remove waste.
- Urine is stored in the:
A) Kidney
B) Urethra
C) Urinary bladder ✅
D) Ureter
Explanation: The bladder temporarily stores urine.
- The functional unit of the kidney is:
A) Alveolus
B) Nephron ✅
C) Neuron
D) Glomerulus
Explanation: Nephrons perform filtration, reabsorption, and secretion.
- Which blood vessel brings blood to the kidney?
A) Renal vein
B) Hepatic artery
C) Renal artery ✅
D) Pulmonary vein
Explanation: Renal artery carries oxygenated blood to the kidney.
- The urethra carries urine from:
A) Kidney to ureter
B) Ureter to bladder
C) Bladder to outside of body ✅
D) Ureter to kidney
Explanation: Urethra is the final pathway for urine excretion.
- What is the main nitrogenous waste in human urine?
A) Ammonia
B) Uric acid
C) Creatinine
D) Urea ✅
Explanation: Urea is the primary nitrogenous waste in urine.
- Which part of the nephron filters blood?
A) Loop of Henle
B) Glomerulus ✅
C) Collecting duct
D) Bowman’s capsule
Explanation: The glomerulus is a network of capillaries for filtration.
- Urine formation does NOT involve:
A) Filtration
B) Reabsorption
C) Assimilation ✅
D) Secretion
Explanation: Assimilation is related to digestion, not excretion.
- Which hormone increases water reabsorption in kidneys?
A) Insulin
B) ADH ✅
C) Glucagon
D) Oxytocin
Explanation: ADH helps conserve water by increasing reabsorption.
- The outer region of the kidney is called:
A) Medulla
B) Cortex ✅
C) Pelvis
D) Hilum
Explanation: The cortex contains glomeruli and proximal/distal tubules.
- Which structure connects kidneys to the bladder?
A) Urethra
B) Loop of Henle
C) Ureters ✅
D) Collecting duct
Explanation: Ureters transport urine from kidneys to bladder.
- What is the normal pH of urine?
A) 2
B) 5–6 ✅
C) 7.5
D) 9
Explanation: Urine is slightly acidic under normal conditions.
- Which organ removes carbon dioxide from the blood?
A) Kidney
B) Lung ✅
C) Skin
D) Liver
Explanation: Lungs excrete carbon dioxide through exhalation.
- Excess water is excreted through:
A) Lungs
B) Skin
C) Kidneys ✅
D) Liver
Explanation: Kidneys regulate water balance through urine.
- The tube that carries urine from kidneys is the:
A) Urethra
B) Ureter ✅
C) Nephron
D) Bladder
Explanation: Each kidney connects to the bladder via a ureter.
- Which waste product is excreted by the liver into bile?
A) Urea
B) Bilirubin ✅
C) Ammonia
D) Carbon dioxide
Explanation: Bilirubin is a bile pigment formed from hemoglobin breakdown.
- Which organ excretes sweat?
A) Kidney
B) Skin ✅
C) Lung
D) Liver
Explanation: Sweat glands in the skin help excrete salts and water.
- Which part of the nephron forms a cup-like structure?
A) Glomerulus
B) Bowman’s capsule ✅
C) Loop of Henle
D) Collecting duct
Explanation: Bowman’s capsule surrounds the glomerulus for filtration.
- Which of the following is NOT a function of the kidneys?
A) Regulation of pH
B) Production of insulin ✅
C) Blood pressure regulation
D) Waste elimination
Explanation: Insulin is produced by the pancreas.
- What is the color of normal urine due to?
A) Hemoglobin
B) Melanin
C) Urobilin ✅
D) Chlorophyll
Explanation: Urobilin is a yellow pigment derived from bilirubin.
🟡 Moderate Level (21–40)
- The loop of Henle is mainly involved in:
A) Filtration
B) Water reabsorption ✅
C) Protein digestion
D) Urine storage
Explanation: The loop concentrates urine by reabsorbing water and salts.
- Which part of the nephron is responsible for selective reabsorption?
A) Bowman’s capsule
B) Proximal convoluted tubule ✅
C) Loop of Henle
D) Ureter
Explanation: The proximal tubule reabsorbs glucose, salts, and water.
- High levels of urea in blood is called:
A) Uremia ✅
B) Glycosuria
C) Albuminuria
D) Hematuria
Explanation: Uremia indicates kidney failure or dysfunction.
- Which hormone regulates sodium reabsorption in kidneys?
A) ADH
B) Aldosterone ✅
C) TSH
D) FSH
Explanation: Aldosterone increases Na+ reabsorption, affecting fluid balance.
- What does the renal pelvis do?
A) Filters blood
B) Reabsorbs glucose
C) Collects urine ✅
D) Regulates hormones
Explanation: It channels urine into the ureter.
- Presence of glucose in urine is termed:
A) Hematuria
B) Glycosuria ✅
C) Ketosis
D) Polyuria
Explanation: Glycosuria is a common symptom of diabetes mellitus.
- Which structure in the nephron is impermeable to water?
A) Descending limb
B) Ascending limb of loop of Henle ✅
C) Collecting duct
D) Proximal tubule
Explanation: This limb allows salt transport but not water.
- Which blood vessel carries filtered blood from the kidney?
A) Renal artery
B) Renal vein ✅
C) Vasa recta
D) Glomerular capillary
Explanation: Renal vein returns deoxygenated, filtered blood to circulation.
- Which metabolic waste is formed from amino acid breakdown?
A) Glucose
B) Urea ✅
C) Glycerol
D) Oxygen
Explanation: Deamination of amino acids forms urea in the liver.
- Which of the following does NOT pass into the glomerular filtrate?
A) Glucose
B) Plasma proteins ✅
C) Urea
D) Ions
Explanation: Proteins are too large to be filtered through glomeruli.
- The kidney is located in the:
A) Thoracic cavity
B) Abdominal cavity ✅
C) Cranial cavity
D) Pelvic cavity
Explanation: Kidneys lie on either side of the spine in the abdomen.
- Excretion through skin is called:
A) Perspiration ✅
B) Filtration
C) Evaporation
D) Digestion
Explanation: Perspiration helps in temperature regulation and excretion.
- Which part of the nephron is highly coiled?
A) Loop of Henle
B) Proximal convoluted tubule ✅
C) Collecting duct
D) Renal artery
Explanation: Its coiled structure maximizes absorption surface area.
- Which ion is critical for acid-base balance in kidneys?
A) Na⁺
B) Cl⁻
C) H⁺ ✅
D) Mg²⁺
Explanation: Kidneys excrete or retain H⁺ to maintain pH.
- Juxtaglomerular apparatus regulates:
A) Blood glucose
B) Blood pressure ✅
C) Filtrate color
D) Sweating
Explanation: It senses blood pressure and releases renin.
- Which disease is associated with crystal deposition in joints due to uric acid?
A) Osteoporosis
B) Gout ✅
C) Arthritis
D) Rickets
Explanation: Gout results from hyperuricemia and urate crystal formation.
- Which of these is NOT excreted by the kidneys?
A) Urea
B) Creatinine
C) Bile pigments ✅
D) Salts
Explanation: Bile pigments are excreted by the liver into feces.
- The fluid entering Bowman’s capsule is called:
A) Urine
B) Filtrate ✅
C) Plasma
D) Lymph
Explanation: This filtrate undergoes further modification to form urine.
- Which condition is caused by failure of kidneys?
A) Anemia
B) Uremia ✅
C) Hypoxia
D) Dyspepsia
Explanation: Uremia results in accumulation of waste in blood.
- The kidney’s filtering capacity per minute is called:
A) Renal absorption
B) Glomerular filtration rate (GFR) ✅
C) Blood pressure
D) Renal clearance
Explanation: GFR indicates how much filtrate is produced per minute.
🔴 Hard Level (41–50)
- Which component is actively secreted into distal tubule?
A) Na⁺
B) K⁺ ✅
C) Glucose
D) Albumin
Explanation: Potassium ions are secreted to maintain electrolyte balance.
- Which enzyme triggers the renin-angiotensin system?
A) Aldosterone
B) Renin ✅
C) ADH
D) Erythropoietin
Explanation: Renin initiates the cascade that increases blood pressure.
- Which process helps concentrate urine in the loop of Henle?
A) Countercurrent mechanism ✅
B) Active transport only
C) Ultrafiltration
D) Osmosis alone
Explanation: The countercurrent multiplier concentrates the filtrate.
- Which protein is produced by kidneys to stimulate RBC formation?
A) Insulin
B) Erythropoietin ✅
C) Renin
D) Albumin
Explanation: Erythropoietin stimulates bone marrow to produce RBCs.
- In chronic kidney disease, dialysis is used to:
A) Cure diabetes
B) Remove waste from blood ✅
C) Deliver insulin
D) Produce urine
Explanation: Dialysis artificially filters blood in place of kidneys.
- Which condition results from kidney’s inability to concentrate urine?
A) Diabetes insipidus ✅
B) Diabetes mellitus
C) Glomerulonephritis
D) Pyelonephritis
Explanation: ADH deficiency causes dilute urine in diabetes insipidus.
- What happens during renal autoregulation?
A) GFR stays constant ✅
B) GFR drops quickly
C) Urine stops forming
D) Glucose is reabsorbed
Explanation: Kidneys maintain a constant GFR despite blood pressure changes.
- What is the minimum urine output needed to remove waste?
A) 100 mL
B) 300 mL
C) 400 mL ✅
D) 800 mL
Explanation: Called “obligatory water loss,” about 400 mL/day is needed.
- Which cells monitor blood pressure in kidneys?
A) Podocytes
B) Macula densa
C) Juxtaglomerular cells ✅
D) Epithelial cells
Explanation: These cells secrete renin in response to low BP.
- Which of the following is used to assess kidney function?
A) Blood pressure
B) Urine volume
C) Creatinine clearance ✅
D) Pulse rate
Explanation: Creatinine clearance estimates GFR and kidney efficiency.
