Free Kidney and Urinary System MCQs with Answers

11. The correct path followed by urine on its way out of the body is

• A. kidney, ureter, bladder, urethra
• B. kidney, urethra, ureter, bladder
• C. bladder, kidney, ureter, urethra
• D. kidney, bladder, ureter, urethra

Explanation: Urine forms in the kidney, runs down the ureter, is stored in the bladder and leaves through the urethra. Mixing up ureter and urethra is the error the options are built to catch.

12. The tube that carries urine from each kidney to the urinary bladder is the

• A. urethra
• B. ureter
• C. nephron
• D. collecting duct

Explanation: Each ureter propels urine by peristalsis from the renal pelvis to the bladder. The urethra is the final exit tube, and the nephron is the microscopic working unit inside the kidney.

13. The capillary tuft enclosed within Bowman's capsule is called the

• A. loop of Henle
• B. peritubular capillary
• C. glomerulus
• D. renal pelvis

Explanation: Blood pressure forces fluid out of the glomerulus into the capsule, the first step of urine formation. The loop of Henle comes later in the tubule, so filtering happens before any reabsorption.

14. Of the roughly 180 litres of glomerular filtrate formed in a day, the amount normally excreted as urine is about

• A. 180 litres
• B. 90 litres
• C. 18 litres
• D. 1.5 litres

Explanation: Over 99 per cent of the filtrate is reabsorbed, leaving roughly a litre and a half of urine. This huge turnover shows how much work the tubules do in reclaiming water and solutes.

15. The main function of the loop of Henle is to

• A. establish a salt gradient in the medulla that allows urine to be concentrated
• B. filter the blood
• C. secrete hormones
• D. store urine before release

Explanation: By pumping salt out of its ascending limb, the loop builds a concentrated medulla that draws water out of the collecting duct. The longer the loop, the more concentrated the urine, which is why desert mammals have such long ones.

16. Besides filtration and reabsorption, the nephron removes drugs, poisons and hydrogen ions from the blood into the tubule fluid by

• A. osmosis
• B. tubular secretion
• C. ultrafiltration
• D. diffusion through the ureter

Explanation: Tubular secretion actively transports selected substances from peritubular capillaries into the tubule, fine tuning both urine composition and blood pH. It is the third urine forming process after filtration and reabsorption.

17. The yellow colour of normal urine is due to

• A. haemoglobin
• B. melanin
• C. the pigment urochrome
• D. chlorophyll breakdown

Explanation: Urochrome, derived from the breakdown of haemoglobin, tints urine in proportion to concentration. Darker urine simply means more pigment per volume of water, a built in hydration meter.

18. The regulation of the water content of the body fluids by the kidneys is called

• A. excretion
• B. thermoregulation
• C. glycolysis
• D. osmoregulation

Explanation: Osmoregulation balances water intake against loss, with ADH adjusting how much water the collecting ducts reclaim. Excretion is the broader removal of wastes, of which water control is one part.

19. Compared with blood in the renal artery, blood leaving the kidney in the renal vein contains

• A. less urea and less oxygen
• B. more urea
• C. more glucose than normal
• D. no red blood cells

Explanation: The kidney removes urea into urine and consumes oxygen for its active transport, so both fall in the outflowing blood. Glucose is conserved, and red cells never leave the vessels.

20. Urine is stored before elimination in the

• A. kidney
• B. urinary bladder
• C. ureter
• D. gall bladder

Explanation: The bladder is a muscular bag that stretches to hold several hundred millilitres until micturition. The gall bladder stores bile, a similarly named but unrelated job.