Question 1: Which of the following forms of nitrogenous waste requires the largest amount of water for its complete elimination from the body?
(a) Uric acid.
(b) Urea.
(c) Ammonia.
(d) Creatinine.
Answer: (c) Ammonia.
Question 2: Ammonotelic animals excrete ammonia primarily through which of the following mechanisms?
(a) Active transport through the kidneys.
(b) Diffusion across body surfaces or gill surfaces as ammonium ions.
(c) Secretion via specialized flame cells.
(d) Filtration through Malpighian tubules.
Answer: (b) Diffusion across body surfaces or gill surfaces as ammonium ions.
Question 3: Terrestrial adaptation in animals necessitated the production of lesser toxic nitrogenous wastes. Which of the following pairs represents these lesser toxic wastes?
(a) Ammonia and Urea.
(b) Urea and Uric acid.
(c) Uric acid and Guanine.
(d) Ammonia and Uric acid.
Answer: (b) Urea and Uric acid.
Question 4: In ureotelic animals, ammonia produced by metabolism is converted into urea in which of the following organs?
(a) Kidney.
(b) Liver.
(c) Spleen.
(d) Pancreas.
Answer: (b) Liver.
Question 5: Reptiles, birds, land snails, and insects predominantly excrete nitrogenous wastes in the form of a pellet or paste. This adaptation is primarily for:
(a) Conserving energy during excretion.
(b) Conservation of water.
(c) Maintaining high body temperature.
(d) Facilitating rapid flight or movement.
Answer: (b) Conservation of water.
Question 6: Protonephridia or flame cells are the primary excretory structures in which of the following organisms?
(a) Earthworm.
(b) Cockroach.
(c) Planaria.
(d) Prawn.
Answer: (c) Planaria.
Question 7: What is the primary function of protonephridia in cephalochordates like Amphioxus?
(a) Nitrogenous waste removal only.
(b) Osmoregulation and ionic and fluid volume regulation.
(c) Synthesis of urea.
(d) Reabsorption of glucose and amino acids.
Answer: (b) Osmoregulation and ionic and fluid volume regulation.
Question 8: Nephridia are the tubular excretory structures of earthworms. Besides removing nitrogenous wastes, they also help in:
(a) Producing urea from ammonia.
(b) Maintaining a fluid and ionic balance.
(c) Synthesizing red blood cells.
(d) Digesting complex carbohydrates.
Answer: (b) Maintaining a fluid and ionic balance.
Question 9: Antennal glands or green glands perform the excretory function in which of the following groups of animals?
(a) Insects.
(b) Arachnids.
(c) Crustaceans.
(d) Annelids.
Answer: (c) Crustaceans.
Question 10: In humans, the kidneys are situated between the levels of which specific vertebrae?
(a) Last thoracic and third lumbar vertebra.
(b) First thoracic and second lumbar vertebra.
(c) Last cervical and first thoracic vertebra.
(d) First lumbar and fifth lumbar vertebra.
Answer: (a) Last thoracic and third lumbar vertebra.
Question 11: Towards the centre of the inner concave surface of the human kidney is a notch called the hilum. Which of the following does NOT enter or exit through the hilum?
(a) Ureter.
(b) Blood vessels.
(c) Nerves.
(d) Urethra.
Answer: (d) Urethra.
Question 12: The renal medulla is divided into a few conical masses that project into the calyces. What are these conical masses called?
(a) Renal columns.
(b) Columns of Bertini.
(c) Medullary pyramids.
(d) Renal pelvis.
Answer: (c) Medullary pyramids.
Question 13: The cortex of the kidney extends in between the medullary pyramids. These cortical extensions are referred to as:
(a) Renal papillae.
(b) Calyces.
(c) Columns of Bertini.
(d) Malpighian corpuscles.
Answer: (c) Columns of Bertini.
Question 14: Each human kidney contains approximately how many complex tubular structures called nephrons?
(a) One hundred thousand.
(b) One million.
(c) Ten million.
(d) Fifty thousand.
Answer: (b) One million.
Question 15: The glomerulus is a tuft of capillaries formed by which of the following blood vessels?
(a) Efferent arteriole.
(b) Renal vein.
(c) Afferent arteriole.
(d) Vasa recta.
Answer: (c) Afferent arteriole.
Question 16: The Malpighian body or renal corpuscle consists of which of the following two structures combined?
(a) Bowman's capsule and PCT.
(b) Glomerulus and Bowman's capsule.
(c) Glomerulus and Efferent arteriole.
(d) PCT and DCT.
Answer: (b) Glomerulus and Bowman's capsule.
Question 17: Which part of the nephron continues immediately after the proximal convoluted tubule (PCT)?
(a) Distal convoluted tubule.
(b) Collecting duct.
(c) Henle's loop.
(d) Renal pelvis.
Answer: (c) Henle's loop.
Question 18: The Malpighian corpuscle, PCT, and DCT of the nephron are strictly situated in which region of the kidney?
(a) Inner medulla.
(b) Outer medulla.
(c) Renal pelvis.
(d) Cortical region.
Answer: (d) Cortical region.
Question 19: In cortical nephrons, the loop of Henle is:
(a) Very long and runs deep into the medulla.
(b) Too short and extends only very little into the medulla.
(c) Completely absent.
(d) Located entirely within the renal pelvis.
Answer: (b) Too short and extends only very little into the medulla.
Question 20: The 'U' shaped minute vessel that runs parallel to the Henle's loop in juxtamedullary nephrons is called:
(a) Peritubular capillary.
(b) Afferent arteriole.
(c) Vasa recta.
(d) Efferent arteriole.
Answer: (c) Vasa recta.
Question 21: The condition of vasa recta in cortical nephrons can be best described as:
(a) Highly developed and long.
(b) Absent or highly reduced.
(c) Forming a complex network around the DCT.
(d) Originating directly from the renal vein.
Answer: (b) Absent or highly reduced.
Question 22: On average, how much blood is filtered by the human kidneys per minute?
(a) 125 ml.
(b) 500-600 ml.
(c) 1100-1200 ml.
(d) 5000 ml.
Answer: (c) 1100-1200 ml.
Question 23: The volume of blood filtered by the kidneys per minute constitutes roughly what fraction of the blood pumped out by each ventricle of the heart in a minute?
(a) 1/10th.
(b) 1/5th.
(c) 1/3rd.
(d) 1/2.
Answer: (b) 1/5th.
Question 24: Glomerular filtration occurs through three layers. Which of the following is NOT one of these layers?
(a) Endothelium of glomerular blood vessels.
(b) Epithelium of Bowman's capsule.
(c) Basement membrane between the endothelium and epithelium.
(d) Smooth muscle layer of the afferent arteriole.
Answer: (d) Smooth muscle layer of the afferent arteriole.
Question 25: The epithelial cells of Bowman's capsule, which are arranged in an intricate manner to leave filtration slits, are called:
(a) Astrocytes.
(b) Podocytes.
(c) Macula densa cells.
(d) Mesangial cells.
Answer: (b) Podocytes.
Question 26: During ultrafiltration in the glomerulus, almost all constituents of the blood plasma pass into the Bowman's capsule EXCEPT:
(a) Glucose.
(b) Amino acids.
(c) Proteins.
(d) Urea.
Answer: (c) Proteins.
Question 27: The glomerular filtration rate (GFR) in a healthy human individual is approximately:
(a) 125 ml/minute.
(b) 1.5 litres/day.
(c) 180 ml/minute.
(d) 5 litres/day.
Answer: (a) 125 ml/minute.
Question 28: Juxta glomerular apparatus (JGA) is a special sensitive region formed by cellular modifications in the:
(a) PCT and afferent arteriole.
(b) DCT and afferent arteriole.
(c) Loop of Henle and vasa recta.
(d) DCT and efferent arteriole.
Answer: (b) DCT and afferent arteriole.
Question 29: A fall in Glomerular Filtration Rate (GFR) activates the JG cells to release which of the following substances?
(a) Erythropoietin.
(b) Angiotensinogen.
(c) Renin.
(d) Aldosterone.
Answer: (c) Renin.
Question 30: Approximately what percentage of the glomerular filtrate is reabsorbed by the renal tubules per day?
(a) 50 per cent.
(b) 75 per cent.
(c) 90 per cent.
(d) 99 per cent.
Answer: (d) 99 per cent.
Question 31: Which of the following substances in the glomerular filtrate are reabsorbed entirely by active transport mechanisms?
(a) Urea and uric acid.
(b) Water and chloride ions.
(c) Glucose and amino acids.
(d) Ammonia and hydrogen ions.
Answer: (c) Glucose and amino acids.
Question 32: Nitrogenous wastes in the renal tubule are primarily absorbed by which mechanism?
(a) Active transport.
(b) Passive transport.
(c) Facilitated diffusion.
(d) Pinocytosis.
Answer: (b) Passive transport.
Question 33: Tubular secretion is an important step in urine formation primarily because it helps in:
(a) Reabsorbing maximum water.
(b) Excreting excess glucose.
(c) Maintenance of ionic and acid-base balance of body fluids.
(d) Producing renin.
Answer: (c) Maintenance of ionic and acid-base balance of body fluids.
Question 34: The Proximal Convoluted Tubule (PCT) is lined by which type of epithelium?
(a) Simple squamous epithelium.
(b) Simple cuboidal brush border epithelium.
(c) Stratified columnar epithelium.
(d) Transitional epithelium.
Answer: (b) Simple cuboidal brush border epithelium.
Question 35: What percentage of electrolytes and water is typically reabsorbed in the Proximal Convoluted Tubule (PCT)?
(a) 10-20 per cent.
(b) 30-40 per cent.
(c) 70-80 per cent.
(d) 90-99 per cent.
Answer: (c) 70-80 per cent.
Question 36: Reabsorption is minimum in which segment of the nephron?
(a) Proximal Convoluted Tubule.
(b) Descending limb of Henle's loop.
(c) Ascending limb of Henle's loop.
(d) Distal Convoluted Tubule.
Answer: (c) Ascending limb of Henle's loop.
Question 37: The descending limb of the loop of Henle has which of the following permeability characteristics?
(a) Permeable to water but almost impermeable to electrolytes.
(b) Impermeable to water but permeable to electrolytes.
(c) Permeable to both water and electrolytes.
(d) Impermeable to both water and electrolytes.
Answer: (a) Permeable to water but almost impermeable to electrolytes.
Question 38: As the filtrate moves down the descending limb of Henle's loop, what happens to its concentration?
(a) It gets diluted.
(b) It remains unchanged.
(c) It becomes highly alkaline.
(d) It gets concentrated.
Answer: (d) It gets concentrated.
Question 39: The ascending limb of the loop of Henle is:
(a) Permeable to water but impermeable to electrolytes.
(b) Impermeable to water but allows transport of electrolytes actively or passively.
(c) The primary site for glucose reabsorption.
(d) Responsible for concentrating the filtrate further.
Answer: (b) Impermeable to water but allows transport of electrolytes actively or passively.
Question 40: Conditional reabsorption of Na+ and water takes place primarily in which part of the renal tubule?
(a) Proximal Convoluted Tubule.
(b) Henle's loop.
(c) Distal Convoluted Tubule.
(d) Bowman's capsule.
Answer: (c) Distal Convoluted Tubule.
Question 41: Large amounts of water could be reabsorbed to produce a concentrated urine from which of the following segments?
(a) Ascending limb of loop of Henle.
(b) Bowman's capsule.
(c) Collecting duct.
(d) Efferent arteriole.
Answer: (c) Collecting duct.
Question 42: Which segment of the nephron allows the passage of small amounts of urea into the medullary interstitium to keep up its osmolarity?
(a) PCT.
(b) DCT.
(c) Collecting duct.
(d) Cortical region of loop of Henle.
Answer: (c) Collecting duct.
Question 43: The flow of filtrate in the two limbs of Henle's loop forms a counter current. A similar counter current pattern is also observed in the flow of blood through the:
(a) Glomerular capillaries.
(b) Peritubular capillaries.
(c) Renal artery and vein.
(d) Vasa recta.
Answer: (d) Vasa recta.
Question 44: The osmolarity of the medullary interstitium increases from the cortex towards the inner medulla. What are the approximate osmolarity values from cortex to inner medulla respectively?
(a) 1200 mOsmolL–1 to 300 mOsmolL–1.
(b) 300 mOsmolL–1 to 1200 mOsmolL–1.
(c) 150 mOsmolL–1 to 600 mOsmolL–1.
(d) 600 mOsmolL–1 to 150 mOsmolL–1.
Answer: (b) 300 mOsmolL–1 to 1200 mOsmolL–1.
Question 45: The concentration gradient in the medullary interstitium is mainly maintained by which two substances?
(a) NaCl and Urea.
(b) Glucose and Amino acids.
(c) Potassium and Bicarbonate.
(d) Ammonia and Hydrogen ions.
Answer: (a) NaCl and Urea.
Question 46: In the counter current mechanism, NaCl is transported by the ascending limb of Henle's loop and is exchanged with the:
(a) Ascending limb of vasa recta.
(b) Descending limb of vasa recta.
(c) Collecting duct.
(d) PCT.
Answer: (b) Descending limb of vasa recta.
Question 47: After NaCl enters the descending limb of the vasa recta, it is returned to the interstitium by the:
(a) Ascending limb of Henle's loop.
(b) Descending limb of Henle's loop.
(c) Ascending portion of vasa recta.
(d) Proximal convoluted tubule.
Answer: (c) Ascending portion of vasa recta.
Question 48: Human kidneys can produce urine that is approximately how many times more concentrated than the initial filtrate formed?
(a) Two times.
(b) Four times.
(c) Eight times.
(d) Ten times.
Answer: (b) Four times.
Question 49: Excessive loss of fluid from the body activates osmoreceptors, which stimulate the hypothalamus to release which hormone?
(a) Aldosterone.
(b) Renin.
(c) Antidiuretic hormone (ADH) or vasopressin.
(d) Atrial Natriuretic Factor (ANF).
Answer: (c) Antidiuretic hormone (ADH) or vasopressin.
Question 50: Antidiuretic hormone (ADH) exerts its primary effect on which part of the excretory system to prevent diuresis?
(a) Glomerulus.
(b) Proximal Convoluted Tubule.
(c) Descending limb of loop of Henle.
(d) Latter parts of the tubule (DCT and Collecting duct).
Answer: (d) Latter parts of the tubule (DCT and Collecting duct).
Question 51: An increase in body fluid volume can complete the osmoregulatory feedback loop by:
(a) Stimulating the release of more ADH.
(b) Switching off the osmoreceptors and suppressing ADH release.
(c) Activating JG cells to secrete renin.
(d) Increasing sympathetic nerve activity to the kidney.
Answer: (b) Switching off the osmoreceptors and suppressing ADH release.
Question 52: Besides water reabsorption, ADH can also affect the kidney by:
(a) Decreasing blood pressure.
(b) Causing constrictory effects on blood vessels.
(c) Increasing the secretion of potassium ions.
(d) Inhibiting the release of aldosterone.
Answer: (b) Causing constrictory effects on blood vessels.
Question 53: Renin is released by JG cells in response to a fall in glomerular blood flow. Renin then converts:
(a) Angiotensin I to Angiotensin II.
(b) Angiotensinogen in blood to Angiotensin I.
(c) Aldosterone to Angiotensin.
(d) Angiotensin II to Angiotensin III.
Answer: (b) Angiotensinogen in blood to Angiotensin I.
Question 54: Angiotensin II is a powerful vasoconstrictor. Its effect on the glomerular filtration rate (GFR) is to:
(a) Decrease the GFR.
(b) Increase the glomerular blood pressure and thereby GFR.
(c) Halt the filtration process entirely.
(d) Have no effect on GFR.
Answer: (b) Increase the glomerular blood pressure and thereby GFR.
Question 55: Angiotensin II activates the adrenal cortex to release which of the following hormones?
(a) Cortisol.
(b) Adrenaline.
(c) Aldosterone.
(d) Vasopressin.
Answer: (c) Aldosterone.
Question 56: What is the primary function of aldosterone in the regulation of kidney function?
(a) It causes reabsorption of Na+ and water from the distal parts of the tubule.
(b) It inhibits the reabsorption of water in the PCT.
(c) It causes vasodilation of the afferent arteriole.
(d) It decreases blood pressure.
Answer: (a) It causes reabsorption of Na+ and water from the distal parts of the tubule.
Question 57: The complex regulatory mechanism involving Renin, Angiotensin, and Aldosterone is commonly known as:
(a) Counter current mechanism.
(b) Micturition reflex.
(c) RAAS (Renin-Angiotensin-Aldosterone System).
(d) ANF feedback loop.
Answer: (c) RAAS (Renin-Angiotensin-Aldosterone System).
Question 58: An increase in blood flow to the atria of the heart can cause the release of which of the following factors?
(a) Renin.
(b) Atrial Natriuretic Factor (ANF).
(c) Antidiuretic Hormone (ADH).
(d) Angiotensinogen.
Answer: (b) Atrial Natriuretic Factor (ANF).
Question 59: What is the physiological effect of Atrial Natriuretic Factor (ANF) on blood vessels and blood pressure?
(a) Vasoconstriction, thereby increasing blood pressure.
(b) Vasodilation, thereby decreasing blood pressure.
(c) No effect on blood vessels, but increases heart rate.
(d) Constriction of the efferent arteriole only.
Answer: (b) Vasodilation, thereby decreasing blood pressure.
Question 60: The ANF mechanism acts as a check on which of the following regulatory systems?
(a) ADH mechanism.
(b) Renin-Angiotensin mechanism.
(c) Micturition reflex.
(d) Counter current mechanism.
Answer: (b) Renin-Angiotensin mechanism.
Question 61: The process of release of urine from the urinary bladder is called:
(a) Excretion.
(b) Secretion.
(c) Micturition.
(d) Defecation.
Answer: (c) Micturition.
Question 62: The initial signal for the micturition reflex is generated by:
(a) Contraction of the urethral sphincter.
(b) Stretching of the urinary bladder as it gets filled with urine.
(c) Release of ADH from the pituitary.
(d) Contraction of the ureters.
Answer: (b) Stretching of the urinary bladder as it gets filled with urine.
Question 63: During the micturition reflex, the central nervous system passes on motor messages that initiate the contraction of which muscles?
(a) Skeletal muscles of the abdomen.
(b) Smooth muscles of the bladder.
(c) Cardiac muscles.
(d) Striated muscles of the ureter.
Answer: (b) Smooth muscles of the bladder.
Question 64: Simultaneous to the contraction of the bladder muscles during micturition, what happens to the urethral sphincter?
(a) It contracts to push urine out.
(b) It relaxes to cause the release of urine.
(c) It undergoes powerful spasms.
(d) It completely shuts off the bladder.
Answer: (b) It relaxes to cause the release of urine.
Question 65: An adult human excretes on average how much urine per day?
(a) 0.5 to 1 litre.
(b) 1 to 1.5 litres.
(c) 2 to 3 litres.
(d) 4 to 5 litres.
Answer: (b) 1 to 1.5 litres.
Question 66: Normal human urine is slightly acidic. What is the approximate average pH of urine?
(a) 4.0.
(b) 6.0.
(c) 7.4.
(d) 8.2.
Answer: (b) 6.0.
Question 67: On an average, how many grams of urea are excreted out per day by a healthy adult human?
(a) 10 - 15 gm.
(b) 25 - 30 gm.
(c) 40 - 50 gm.
(d) 100 - 150 gm.
Answer: (b) 25 - 30 gm.
Question 68: The presence of which of the following substances in urine is indicative of diabetes mellitus?
(a) Urea and uric acid.
(b) Creatinine and ammonia.
(c) Glucose and ketone bodies.
(d) Proteins and red blood cells.
Answer: (c) Glucose and ketone bodies.
Question 69: The lungs help in the elimination of excretory wastes by removing large amounts of:
(a) Urea.
(b) Carbon dioxide and water.
(c) Ammonia and salts.
(d) Uric acid.
Answer: (b) Carbon dioxide and water.
Question 70: Approximately how much CO2 is removed by our lungs every minute?
(a) 50 mL/minute.
(b) 100 mL/minute.
(c) 200 mL/minute.
(d) 500 mL/minute.
Answer: (c) 200 mL/minute.
Question 71: The liver secretes bile-containing substances which eventually pass out along with digestive wastes. Which of the following is NOT typically eliminated through bile?
(a) Bilirubin and biliverdin.
(b) Cholesterol.
(c) Degraded steroid hormones.
(d) Urea.
Answer: (d) Urea.
Question 72: Sweat is a watery fluid produced by the sweat glands. Its primary function is to facilitate a cooling effect on the body surface, but it also helps remove:
(a) Sebum and waxes.
(b) NaCl, small amounts of urea, and lactic acid.
(c) Sterols and hydrocarbons.
(d) Bilirubin and cholesterol.
Answer: (b) NaCl, small amounts of urea, and lactic acid.
Question 73: Sebaceous glands eliminate certain substances to provide a protective oily covering for the skin. These substances are primarily excreted through:
(a) Sweat.
(b) Sebum.
(c) Saliva.
(d) Tears.
Answer: (b) Sebum.
Question 74: Which of the following substances are eliminated through sebum by the sebaceous glands?
(a) Lactic acid and urea.
(b) Sterols, hydrocarbons, and waxes.
(c) Bilirubin and vitamins.
(d) Ammonia and sodium chloride.
Answer: (b) Sterols, hydrocarbons, and waxes.
Question 75: Small amounts of nitrogenous wastes can also be eliminated through which of the following alternative routes?
(a) Cerebrospinal fluid.
(b) Tears.
(c) Saliva.
(d) Synovial fluid.
Answer: (c) Saliva.
Question 76: Malfunctioning of kidneys can lead to the accumulation of urea in the blood. What is this highly harmful condition called?
(a) Hematuria.
(b) Uremia.
(c) Ketonuria.
(d) Glycosuria.
Answer: (b) Uremia.
Question 77: In patients suffering from uremia, urea can be successfully removed by using an artificial kidney. This process is called:
(a) Peritoneal dialysis.
(b) Hemodialysis.
(c) Kidney transplantation.
(d) Lithotripsy.
Answer: (b) Hemodialysis.
Question 78: During hemodialysis, blood drained from a convenient artery is pumped into a dialysing unit after adding an anticoagulant. Which anticoagulant is typically used?
(a) Warfarin.
(b) EDTA.
(c) Heparin.
(d) Citrate.
Answer: (c) Heparin.
Question 79: The dialysing unit contains a coiled cellophane tube surrounded by a dialysing fluid. This fluid has the same composition as blood plasma EXCEPT for the absence of:
(a) Glucose.
(b) Amino acids.
(c) Proteins.
(d) Nitrogenous wastes.
Answer: (d) Nitrogenous wastes.
Question 80: The porous cellophane membrane of the dialysing tube allows the passage of molecules based on:
(a) Active transport utilizing ATP.
(b) Concentration gradient.
(c) Facilitated diffusion via carrier proteins.
(d) Endocytosis.
Answer: (b) Concentration gradient.
Question 81: After the blood is cleared of nitrogenous wastes in the dialyser, it is pumped back to the body through a vein. What is added to the blood before returning it to the body?
(a) Extra urea to maintain osmolarity.
(b) Anti-heparin.
(c) More heparin to prevent clotting in the vein.
(d) Renin to maintain blood pressure.
Answer: (b) Anti-heparin.
Question 82: What is the ultimate method recommended for the correction of acute renal failures?
(a) Continuous lifelong hemodialysis.
(b) Kidney transplantation.
(c) High-dose diuretic therapy.
(d) Strict protein-free diet.
Answer: (b) Kidney transplantation.
Question 83: In kidney transplantation, a functioning kidney from a donor is used. Why is a close relative preferred as a donor?
(a) To ensure the kidney is physically the exact same size.
(b) To minimise the chances of rejection by the immune system of the host.
(c) Because relatives have the same blood volume.
(d) Because the surgical procedure is easier.
Answer: (b) To minimise the chances of rejection by the immune system of the host.
Question 84: Glomerulonephritis is an excretory system disorder characterized by:
(a) Inflammation of glomeruli of kidney.
(b) Formation of stone or insoluble mass in the kidney.
(c) Accumulation of uric acid crystals in joints.
(d) Inability to produce antidiuretic hormone.
Answer: (a) Inflammation of glomeruli of kidney.
Question 85: Renal calculi refers to the formation of stones or insoluble masses of crystallized salts within the kidney. These stones are mostly composed of:
(a) Uric acid.
(b) Oxalates.
(c) Cholesterol.
(d) Calcium carbonate.
Answer: (b) Oxalates.
Question 86: The process of maintaining optimal water and ionic concentration in the internal environment of the body is termed:
(a) Excretion.
(b) Ultrafiltration.
(c) Osmoregulation.
(d) Micturition.
Answer: (c) Osmoregulation.
Question 87: Urea is formed from ammonia in the liver via a specific biochemical pathway known as:
(a) Krebs cycle.
(b) Calvin cycle.
(c) Ornithine cycle.
(d) Cori cycle.
Answer: (c) Ornithine cycle.
Question 88: In marine fishes, which of the following is the primary nitrogenous waste excreted?
(a) Uric acid.
(b) Ammonia.
(c) Trimethylamine oxide.
(d) Urea.
Answer: (d) Urea.
Question 89: Some amount of urea may be retained in the kidney matrix of some ureotelic animals. What is the physiological significance of this retention?
(a) To prevent uric acid stone formation.
(b) To maintain a desired osmolarity in the medullary interstitium.
(c) To provide an energy source for kidney cells.
(d) To act as a buffer against acidic pH.
Answer: (b) To maintain a desired osmolarity in the medullary interstitium.
Question 90: Which sequence correctly depicts the path of urine flow in the human excretory system?
(a) Kidney → Urinary bladder → Ureter → Urethra.
(b) Kidney → Ureter → Urinary bladder → Urethra.
(c) Urethra → Urinary bladder → Ureter → Kidney.
(d) Kidney → Ureter → Urethra → Urinary bladder.
Answer: (b) Kidney → Ureter → Urinary bladder → Urethra.
Question 91: The structural and functional units of the kidney are the nephrons. Approximately how many nephrons are present in both kidneys combined in a normal adult human?
(a) One million.
(b) Two million.
(c) Three million.
(d) Four million.
Answer: (b) Two million.
Question 92: The Bowman's capsule and the glomerulus together constitute the Malpighian body. The endothelium of the glomerular capillaries has minute pores known as:
(a) Slit pores.
(b) Fenestrations.
(c) Aquaporins.
(d) Plasmodesmata.
Answer: (b) Fenestrations.
Question 93: Which specific part of the nephron plays a significant role in maintaining the high osmolarity of the medullary interstitial fluid?
(a) Proximal Convoluted Tubule.
(b) Distal Convoluted Tubule.
(c) Henle's Loop.
(d) Glomerulus.
Answer: (c) Henle's Loop.
Question 94: During the selective secretion process in the Proximal Convoluted Tubule (PCT), which of the following ions are secreted into the filtrate to maintain pH?
(a) Sodium and Potassium.
(b) Hydrogen ions and Ammonia.
(c) Bicarbonate and Chloride.
(d) Calcium and Magnesium.
Answer: (b) Hydrogen ions and Ammonia.
Question 95: Which portion of the nephron actively or passively transports electrolytes out into the medullary fluid, thereby diluting the concentrated filtrate as it passes upward?
(a) Descending limb of Henle's loop.
(b) Proximal Convoluted Tubule.
(c) Ascending limb of Henle's loop.
(d) Collecting duct.
Answer: (c) Ascending limb of Henle's loop.
Question 96: What triggers the activation of osmoreceptors in the body?
(a) Only a decrease in blood volume.
(b) Only an increase in ionic concentration.
(c) Changes in blood volume, body fluid volume, and ionic concentration.
(d) Variations in atmospheric pressure.
Answer: (c) Changes in blood volume, body fluid volume, and ionic concentration.
Question 97: Atrial Natriuretic Factor (ANF) acts as a powerful vasodilator. It is synthesized and secreted by the:
(a) Juxtaglomerular cells of the kidney.
(b) Adrenal cortex.
(c) Atrial wall of the heart.
(d) Posterior pituitary gland.
Answer: (c) Atrial wall of the heart.
Question 98: Micturition is a reflex action. The motor signals that cause the contraction of the smooth muscles of the bladder are transmitted through:
(a) Somatic neural system.
(b) Sympathetic neural system.
(c) Parasympathetic neural system.
(d) Enteric nervous system.
Answer: (c) Parasympathetic neural system.
Question 99: When a patient experiences glycosuria and ketonuria, the most probable diagnosis is:
(a) Glomerulonephritis.
(b) Uremia.
(c) Diabetes insipidus.
(d) Diabetes mellitus.
Answer: (d) Diabetes mellitus.
Question 100: Which of the following statements correctly differentiates between cortical and juxtamedullary nephrons?
(a) Cortical nephrons have long loops of Henle, while juxtamedullary nephrons have short ones.
(b) Vasa recta is highly developed in cortical nephrons and absent in juxtamedullary nephrons.
(c) Juxtamedullary nephrons have loops of Henle that run deep into the medulla, whereas cortical nephrons do not.
(d) Cortical nephrons lack a glomerulus, which is present in juxtamedullary nephrons.
Answer: (c) Juxtamedullary nephrons have loops of Henle that run deep into the medulla, whereas cortical nephrons do not.
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