Free Kidney and Urinary System MCQs with Answers

41. ADH acts on the

• A. Proximal tubule
• B. Descending limb
• C. Collecting duct
• D. Glomerulus

Explanation: ADH (vasopressin) increases water permeability of the collecting duct by inserting aquaporins.

42. The loop of Henle creates

• A. Blood pressure
• B. Concentration gradient in medulla
• C. Glomerular filtrate
• D. Urea

Explanation: The counter-current multiplier in the loop of Henle establishes a hypertonic gradient in the renal medulla.

43. Urea is formed in the

• A. Kidneys
• B. Liver
• C. Muscles
• D. Brain

Explanation: Urea is formed in the liver from ammonia (toxic) via the ornithine/urea cycle.

44. Renin is secreted by

• A. Adrenal cortex
• B. Juxtaglomerular cells
• C. Pituitary
• D. Hypothalamus

Explanation: Juxtaglomerular cells in the afferent arteriole secrete renin in response to low blood pressure.

45. Glycosuria occurs when

• A. Blood glucose is normal
• B. Blood glucose exceeds renal threshold
• C. ADH is high
• D. Aldosterone is low

Explanation: Glycosuria (glucose in urine) occurs when blood glucose exceeds the renal threshold (~180 mg/dL), saturating reabsorption capacity.

46. The RAAS pathway ultimately increases

• A. Blood pressure
• B. Urine output
• C. Sodium excretion
• D. Potassium reabsorption

Explanation: The renin-angiotensin-aldosterone system (RAAS) ultimately increases blood pressure through vasoconstriction and Na+/water retention.

47. Diabetes insipidus is caused by

• A. Insulin deficiency
• B. ADH deficiency
• C. Aldosterone excess
• D. Renin deficiency

Explanation: Diabetes insipidus results from ADH deficiency or resistance, causing inability to concentrate urine and excessive dilute urine.

48. Kidneys perform their osmoregulatory role under the effect of Antidiuretic Hormone, which type of urine is produced in this situation?

• A. Hypotonic urine with decreased volume
• B. Hypotonic urine with increased volume
• C. Hypertonic urine with decreased volume
• D. Hypertonic urine with increased volume

Explanation: ADH makes the distal tubule and collecting duct permeable to water, so water is reabsorbed into the salty medulla and a small volume of concentrated urine leaves. Concentrated means hypertonic, and reabsorbing water necessarily reduces the volume, so the two halves of the answer must move together. Hypotonic urine of large volume is what appears when ADH is absent, as in diabetes insipidus.

49. The process of osmoregulation refers to:

• A. The filtration of blood to remove metabolic waste
• B. The regulation of solute and water movement between an organism and its environment
• C. The creation of an osmotic gradient in the kidney medulla
• D. The secretion of hormones that control blood plasma

Explanation: Osmoregulation is the control of water and solute balance so that the water potential of body fluids stays steady, whatever the organism drinks or loses. Filtering waste out of the blood is excretion, a related but separate process, and it is the closest distractor. The medullary gradient is one mechanism the kidney uses to achieve osmoregulation, not the definition of it.