Q: A patient has a glomerular filtration rate (GFR) of 125 mL/min. How much plasma is filtered by the kidneys in one day? Use $$1\ \text{day} = 1440\ \text{minutes}.$$

$$125\ \text{mL/min} \times 1440\ \text{min} = 180,000\ \text{mL} = 180\ \text{L}$$

Q: If the hydrostatic pressure in the glomerular capillaries is 55 mm Hg, the colloid osmotic pressure is 30 mm Hg, and the fluid pressure in Bowman’s capsule is 15 mm Hg, what is the net driving force for filtration?

$$55\ \text{mm Hg} - (30\ \text{mm Hg} + 15\ \text{mm Hg}) = 10\ \text{mm Hg}$$

Q: A patient’s urine output is 2 L/day, and the amount of filtrate produced is 180 L/day. What percentage of the filtrate is reabsorbed?

$$\frac{180 - 2}{180} \times 100\% = 98.9\%$$

Question 1

Which of the following best describes the primary function of the kidneys in maintaining homeostasis?

Accepted Answer

They regulate extracellular fluid volume, blood pressure, and osmolarity.

Question 2

A patient has a glomerular filtration rate (GFR) of 125 mL/min. How much plasma is filtered by the kidneys in one day? Use $$1\ 	ext{day} = 1440\ 	ext{minutes}.$$

Accepted Answer

$$125\ 	ext{mL/min} 	imes 1440\ 	ext{min} = 180,000\ 	ext{mL} = 180\ 	ext{L}$$

Question 3

Which of the following would most likely increase the glomerular filtration rate (GFR)?

Accepted Answer

An increase in hydrostatic pressure in the glomerular capillaries

Question 4

If the hydrostatic pressure in the glomerular capillaries is 55 mm Hg, the colloid osmotic pressure is 30 mm Hg, and the fluid pressure in Bowman’s capsule is 15 mm Hg, what is the net driving force for filtration?

Accepted Answer

$$55\ 	ext{mm Hg} - (30\ 	ext{mm Hg} + 15\ 	ext{mm Hg}) = 10\ 	ext{mm Hg}$$

Question 5

Which of the following best explains why glucose is normally not found in urine?

Accepted Answer

Glucose is reabsorbed in the proximal tubule by sodium-dependent transporters.

Question 6

A patient’s urine output is 2 L/day, and the amount of filtrate produced is 180 L/day. What percentage of the filtrate is reabsorbed?

Accepted Answer

$$\frac{180 - 2}{180} 	imes 100\% = 98.9\%$$

Question 7

Which of the following is a correct sequence of urine flow through the nephron and urinary tract?

Accepted Answer

Glomerulus → proximal tubule → loop of Henle → distal tubule → collecting duct → renal pelvis → ureter → bladder

Question 8

Which process is responsible for the movement of substances from the peritubular capillaries into the nephron tubule?

Accepted Answer

Secretion

Question 9

Which hormone is most directly involved in the regulation of glomerular filtration rate (GFR) via smooth muscle contraction?

Accepted Answer

Angiotensin II

Question 10

A patient has a plasma creatinine clearance of 120 mL/min. What does this value most closely represent?

Accepted Answer

The patient’s glomerular filtration rate (GFR)

Question 11

Which of the following would most likely occur if the afferent arteriole of the nephron constricts?

Accepted Answer

Decrease in glomerular filtration rate (GFR)

Question 12

Which of the following best describes the role of peritubular capillaries?

Accepted Answer

They reabsorb water and solutes from the nephron back into the blood.

Question 13

Which of the following substances is primarily secreted into the nephron tubule to regulate acid-base balance?

Accepted Answer

Hydrogen ions ($$	ext{H}^+)$$

Question 14

Which of the following best explains why the clearance of inulin is used to measure GFR?

Accepted Answer

Inulin is freely filtered and neither reabsorbed nor secreted.

Question 15

Which of the following is true regarding the micturition reflex?

Accepted Answer

It involves contraction of the bladder’s smooth muscle and relaxation of the external sphincter.

Question 16

Which of the following would most likely result from a decrease in plasma protein concentration?

Accepted Answer

Increase in glomerular filtration rate (GFR)

Question 17

Which of the following best describes the effect of sympathetic nervous system activation on the urinary bladder?

Accepted Answer

It inhibits contraction of the bladder’s smooth muscle and contracts the internal sphincter.

Question 18

Which of the following is the best definition of renal clearance?

Accepted Answer

The volume of plasma from which a substance is completely removed by the kidneys per unit time.

Question 19

Which of the following would most likely decrease the amount of filtrate formed in the kidneys?

Accepted Answer

Increased hydrostatic pressure in Bowman’s capsule

Question 20

Which of the following is a consequence of competition for renal carriers during secretion?

Accepted Answer

Slowed secretion of molecules that use the same carrier

Chapter 19

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