Free Kidney and Urinary System MCQs with Answers

• A. the total of all chemical reactions in the body
• B. the removal of metabolic waste from the body
• C. the maintenance of a constant internal environment despite changes outside the body
• D. the growth of an organism to a fixed adult size

Explanation: Homeostasis keeps temperature, water potential, blood glucose and pH within narrow limits, because enzymes work properly only over a small…

• A. nephron
• B. neuron
• C. alveolus
• D. ureter

Explanation: Each kidney contains about a million nephrons, and every one carries out filtration, reabsorption and secretion on its own, so the organ's…

• A. active transport using ATP from the capsule cells
• B. the high hydrostatic pressure caused by the efferent arteriole being narrower than the afferent
• C. osmosis from the tubule into the capillary
• D. the beating of cilia in the capsule

Explanation: Blood enters the glomerulus through a wide afferent arteriole and leaves through a narrower efferent one, so pressure builds up and forces…

• A. Glucose
• B. Urea
• C. Sodium ions
• D. Plasma proteins

Explanation: The basement membrane acts as the real molecular sieve and holds back anything much larger than about 68,000 relative molecular mass, so…

• A. proximal convoluted tubule
• B. collecting duct
• C. loop of Henle
• D. Bowman's capsule

Explanation: The proximal tubule cells carry microvilli and many mitochondria because glucose and amino acids are recovered here by active transport…

• A. a larger Bowman's capsule
• B. more glomeruli per kidney
• C. a much longer loop of Henle, which builds a steeper salt gradient in the medulla
• D. no collecting ducts

Explanation: The loop works as a countercurrent multiplier, making the medulla progressively saltier towards the tip, and the collecting duct passing…

• A. increasing the rate of glomerular filtration
• B. making the walls of the distal tubule and collecting duct more permeable to water
• C. actively pumping water out of the tubule
• D. reducing the reabsorption of sodium ions

Explanation: ADH from the posterior pituitary inserts water channels into the tubule walls, so more water is reabsorbed by osmosis into the salty…

• A. diabetes mellitus
• B. kidney stones
• C. a urinary tract infection
• D. diabetes insipidus

Explanation: Diabetes insipidus results from a lack of ADH or a failure of the tubule to respond to it, so water cannot be reabsorbed and the patient…

• A. sodium ions
• B. glucose
• C. urea
• D. plasma proteins

Explanation: Aldosterone stimulates the distal tubule and collecting duct to pump sodium back into the blood in exchange for potassium, and since water…

• A. the blood glucose level exceeds the capacity of the tubule carriers to reabsorb it
• B. glucose is too large to be reabsorbed
• C. the glomerulus stops filtering glucose
• D. insulin is secreted into the filtrate

Explanation: Reabsorption of glucose depends on a fixed number of carrier proteins in the proximal tubule, and once the blood concentration passes the…

• 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.

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

Explanation: Each ureter propels urine by peristalsis from the renal pelvis to the bladder.

• 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.

• 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.

• 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.

• 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…

• 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.

• 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.

• 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.

• 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.