Q40. Which structures in the human kidney remove soluble nitrogenous wastes from the blood?
[SSC MTS 2025 Cycle (held 11 February 2026)]
(a) Urethra
(b) Nephrons
(c) ATP molecules
(d) Xylem vessels
Answer: (b) Nephrons
Explanation: Nephrons are microscopic filtering and urine-forming units inside the kidneys. They filter plasma at the renal corpuscle, selectively reabsorb useful substances and eliminate nitrogenous wastes through urine. The urethra merely carries urine outside the body and does not filter blood.
Q39. Which of the following are selectively reabsorbed from the initial kidney filtrate: I. glucose; II. amino acids?
[SSC CHSL Tier-I (17 November 2025)]
(a) Only I
(b) Only II
(c) Both I and II
(d) Neither I nor II
Answer: (c) Both I and II
Explanation: Both glucose and amino acids pass into the initial glomerular filtrate because they are small molecules. In a healthy person, the proximal convoluted tubule normally reabsorbs almost all of them into the bloodstream, preventing their unnecessary loss in the final urine.
Q38. What is the principal function of an artificial kidney?
[SSC CHSL Tier-I (14 November 2025)]
(a) Production of urine inside the patient
(b) Removal of nitrogenous wastes from the blood
(c) Increasing the blood glucose level
(d) Raising blood pressure directly
Answer: (b) Removal of nitrogenous wastes from the blood
Explanation: An artificial kidney, or dialyser, helps remove urea, creatinine and excess water from circulating blood when kidney filtration is inadequate. It uses a semipermeable membrane and dialysing fluid but does not fully reproduce every hormonal and regulatory function of natural kidneys.
Q37. Which nephron segment chiefly establishes the osmotic gradient needed to concentrate urine?
[RRB NTPC Graduate Level (18 June 2025, Shift I)]
(a) Distal convoluted tubule
(b) Proximal convoluted tubule
(c) Collecting duct
(d) Loop of Henle
Answer: (d) Loop of Henle
Explanation: The loop of Henle generates the medullary osmotic gradient through countercurrent multiplication. Its descending and ascending limbs differ in permeability to water and salts. This gradient enables the collecting ducts, particularly under antidiuretic hormone influence, to produce concentrated urine.
Q36. Which pairing of a human urinary organ with its number is incorrect?
[RRB Technician Grade III (December 2024)]
(a) Ureters — one pair
(b) Urinary bladder — one
(c) Kidneys — one pair
(d) Urethras — one pair
Answer: (d) Urethras — one pair
Explanation: The normal human urinary tract consists of two kidneys, two ureters, one urinary bladder and one urethra. The ureters lead from each kidney to the bladder. The single urethra conducts stored urine to the exterior during urination.
Q35. Consider the statements:
(i) kidneys lie in the thoracic cavity;
(ii) urine is stored in the urinary bladder;
(iii) lungs remove carbon dioxide.
Which statement is incorrect?
[RRB Technician Grade III (26 December 2024, Shift II)]
(a) Only (i)
(b) Only (ii)
(c) Both (i) and (iii)
(d) All three
Answer: (a) Only (i)
Explanation: Kidneys are retroperitoneal organs located in the posterior abdominal region, not the thoracic cavity. The urinary bladder stores urine until micturition. The lungs also participate in excretion by removing carbon dioxide and water vapour during breathing.
Q34. What is the cup-shaped structure surrounding the glomerulus in a nephron?
[RRB ALP Stage I (28 November 2024, Shift I)]
(a) Proximal convoluted tubule
(b) Bowman’s capsule
(c) Distal convoluted tubule
(d) Loop of Henle
Answer: (b) Bowman’s capsule
Explanation: Bowman’s capsule is the double-walled cup surrounding the tuft of glomerular capillaries. Together they form the renal corpuscle, where plasma is filtered through a specialised barrier. Filtrate enters Bowman’s space before passing into the proximal convoluted tubule.
Q33. Why is urine formed in the human body?
[RRB ALP Stage I (29 November 2024, Shift III)]
(a) To empty the bladder alone
(b) To eliminate dissolved metabolic wastes from blood
(c) To filter blood entering the heart directly
(d) To remove carbon dioxide through the lungs
Answer: (b) To eliminate dissolved metabolic wastes from blood
Explanation: Urine formation allows kidneys to clear urea and other metabolic wastes and regulate water, electrolyte and acid-base balance. Filtration is followed by selective reabsorption and tubular secretion. Emptying the bladder is a subsequent process rather than the purpose of forming urine.
Q32. What are the numerous microscopic filtration units present inside human kidneys called?
[SSC CGL Tier-I (18 September 2024, Shift II)]
(a) Alveoli
(b) Nephrons
(c) Villi
(d) Axons
Answer: (b) Nephrons
Explanation: Each kidney contains approximately one million nephrons. A nephron contains a renal corpuscle and tubule, enabling filtration, reabsorption and secretion. Alveoli belong to the lungs, villi enhance intestinal absorption, and axons conduct nerve impulses.
Q31. Which listed structure of a nephron receives the fluid filtered from the glomerular blood capillaries?
[UPSC NDA General Ability Test (1 September 2024)]
(a) Collecting duct
(b) Renal vein
(c) Ureter
(d) Bowman’s capsule
Answer: (d) Bowman’s capsule
Explanation: Blood filtration occurs across glomerular capillaries into Bowman’s capsule, whose cavity collects the filtrate. The collecting duct receives processed tubular fluid later. Neither the ureter nor renal vein is part of the filtration surface of the nephron.