Question 1

Which of the following best describes the main function of tubular reabsorption in the nephron?

Accepted Answer

It reclaims most of the filtrate and returns it to the blood, conserving water and solutes.

Question 2

Which route of tubular reabsorption involves the movement of substances through the cytosol of tubule cells?

Accepted Answer

Transcellular route

Question 3

Which of the following substances is primarily reabsorbed via the paracellular route in the proximal convoluted tubule (PCT)?

Accepted Answer

Water

Question 4

The Na+-K+ ATPase pump is crucial for sodium reabsorption in the nephron. What is the main effect of this pump?

Accepted Answer

It pumps sodium into the interstitial space, creating a gradient for sodium entry from the filtrate.

Question 5

Which hormone increases water reabsorption in the collecting ducts by inserting aquaporins into the apical membrane?

Accepted Answer

Antidiuretic hormone (ADH)

Question 6

A patient with diabetes mellitus has glucose present in their urine. This is most likely due to:

Accepted Answer

Saturation of glucose transporters, exceeding the transport maximum (Tm)

Question 7

Which segment of the nephron is impermeable to water but allows solute reabsorption, especially Na+ and Cl-?

Accepted Answer

Ascending limb of the nephron loop

Question 8

Which hormone acts on the distal convoluted tubule (DCT) to increase calcium reabsorption?

Accepted Answer

Parathyroid hormone (PTH)

Question 9

The countercurrent multiplier mechanism in the nephron loop is essential for:

Accepted Answer

Establishing the medullary osmotic gradient necessary for urine concentration

Question 10

Calculate the renal clearance (C) for a substance if the urine concentration (U) is 10 mg/ml, urine flow rate (V) is 2 ml/min, and plasma concentration (P) is 0.5 mg/ml. Use the formula $$C = \frac{UV}{P}.$$

Accepted Answer

$$C = 40 ml/$$min$

Question 11

Which of the following is a primary function of tubular secretion?

Accepted Answer

Disposing of substances bound to plasma proteins, such as drugs

Question 12

A patient presents with a GFR of 50 ml/min for over 3 months. Which condition does this most likely indicate?

Accepted Answer

Chronic renal disease

Question 13

Which of the following would most likely result in the formation of a large volume of dilute urine?

Accepted Answer

Decreased production of ADH

Question 14

Which of the following best explains why lipid-soluble drugs can be difficult to eliminate from the body via the kidneys?

Accepted Answer

They are reabsorbed passively along with water down their concentration gradients.

Question 15

Which of the following is NOT a normal constituent of urine?

Accepted Answer

Glucose

Question 16

A patient with severe dehydration is expected to have which of the following urine characteristics?

Accepted Answer

High osmolality and deep yellow color

Question 17

Which of the following best describes the effect of aldosterone on the nephron?

Accepted Answer

It increases the synthesis of Na+ and K+ channels and Na+-K+ ATPases, promoting Na+ reabsorption.

Question 18

Which of the following is a likely consequence of a kidney stone lodged in the ureter?

Accepted Answer

Obstruction of urine flow and severe pain

Question 19

Which of the following is a correct sequence for the events required for micturition (urination) in adults?

Accepted Answer

Contraction of detrusor muscle, opening of internal urethral sphincter, opening of external urethral sphincter

Question 20

Which of the following congenital abnormalities is characterized by the fusion of the kidneys across the midline, forming a single U-shaped organ?

Accepted Answer

Horseshoe kidney

Tubular Reabsorption and Secretion: Mechanisms and Regulation in the Urinary System

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