Renal Physiology: Guyton Chapter 29 - 32

Question 1

[27-minute video]: Guyton and Hall Medical Physiology (Chapter 29) - Urine Concentration and Dilution

Answer 1

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Question 2

[35-minute video]: Guyton and Hall Medical Physiology (Chapter 30) - Renal handling of K, Ca, P, Mg and ECF

Answer 2

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Question 3

[6-minute video]: Vasa Recta Counter Current Exchange

Answer 3

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Question 4

Define renal clearance.

Answer 4

This is the volume of plasma that is cleared of a substance per unit time through the kidney.

Question 5

Explain how diabetes insipidus causes increased urinary volume.

Answer 5

✔ Diabetes insipidus is characterized by a deficiency of antidiuretic hormone (ADH) or a failure of the kidneys to respond to ADH.
✔ ADH stimulates reabsorption of water, so when it is lacking or ineffective, the kidneys release large amounts of dilute urine.

Question 6

Explain how diabetes mellitus causes increased urinary volume.

Answer 6

In diabetes mellitus, high blood glucose levels exceed the kidney’s ability to reabsorb glucose. The excess glucose in the urine draws more water into the urine through osmosis, resulting in increased urinary volume.

Question 7

Explain how infusion of mannitol causes increased urinary volume.

Answer 7

✔ Mannitol is an osmotic diuretic.
✔ It is poorly reabsorbed in the renal tubules.
✔ Because of this, it remains in the tubular fluid, increasing its osmolarity and preventing water reabsorption.
✔ This leads to an increase in urine production and volume.

Question 8

Atrial natriuretic peptide decreases formation of all the following except:
(a) aldosterone
(b) angiotensin III
(c) vasopressin
(d) cyclic GMP
(e) renin

Answer 8

(d) cyclic GMP

Question 9

Urinary volume is increased by all the following except ________.
(a) diabetes insipidus
(b) increased renal arterial pressure
(c) sympathetic stimulation
(d) infusion of mannitol
(e) diabetes mellitus

Answer 9

(c) sympathetic stimulation

Question 10

If fluid is lost from the intravascular compartment ________.
(a) there is a gradual movement of fluid from other compartments as a compensation, which is usually complete
(b) there is limited compensation of movement of fluid from other compartments
(c) the volumes of the other compartments do not change
(d) the fluid moves from other compartments to the intravascular compartment within seconds
(e) none of the above

Answer 10

(a) there is a gradual movement of fluid from other compartments as a compensation, which is usually complete

Question 11

The volume of plasma needed each minute to supply a substance at the rate at which it is excreted in the urine is known as the ________.
(a) filtration rate of the substance
(b) extraction ratio of the substance
(c) diffusion constant of the substance
(d) clearance of the substance
(e) tubular mass of the substance

Answer 11

(d) clearance of the substance

Question 12

With respect to the counter current system
(a) the loops of Henle act as counter current exchangers
(b) solutes diffuse out of vessels conducting blood toward the cortex
(c) water diffuses out of ascending vessels
(d) water diffuses into the collecting ducts
(e) counter current exchange is passive and can operate even if counter current multiplication ceases

Answer 12

(e) counter current exchange is passive and can operate even if counter current multiplication ceases

Question 13

The vasa recta ________.
(a) are the straight portions of the proximal tubules found just proximal to the loops of Henle
(b) extend from the efferent arterioles of the superficial cortical nephrons
(c) are the microvilli found on the cells of the macula densa
(d) comprise the capillary network found in the medulla of the kidney
(e) are the small straight segments of afferent arterioles found directly next to the macula densa

Answer 13

(d) comprise the capillary network found in the medulla of the kidney

Question 14

Which of the following changes tends to increase urinary Ca²⁺ excretion?
(a) Metabolic acidosis
(b) Increased plasma phosphate concentration
(c) Decreased blood pressure
(d) Extracellular fluid volume expansion
(e) Increased plasma parathyroid hormone concentration

Answer 14

(d) Extracellular fluid volume expansion

Question 15

Which part of the renal tubule would have the lowest tubular fluid osmolarity in a patient who has complete lack antidiuretic hormone due to “central” diabetes insipidus?
(a) Early distal tubule
(b) Collecting tubule
(c) Proximal tubule
(d) Medullary collecting duct
(e) Descending loop of Henle

Answer 15

(a) Early distal tubule

Question 16

In acidosis, most of the hydrogen ions secreted by the proximal tubule are associated with which of the following processes?
(a) reabsorption of phosphate ions
(b) reabsorption of bicarbonate ions
(c) reabsorption of potassium ions
(d) excretion of NH₄⁺
(e) excretion of hydrogen ions

Answer 16

(b) reabsorption of bicarbonate ions

Question 17

Persons with nephrogenic diabetes insipidus
(a) produce concentrated urine
(b) lack hormone ADH
(c) may present with excess water in the body
(d) may lack V2 receptors
(e) have low serum levels of urea

Answer 17

(d) may lack V2 receptors

Explanation:
NDI can result from mutations or defects in the V2 receptors (vasopressin receptors) in the kidneys, which are responsible for mediating the effects of ADH. Without functional V2 receptors, the kidneys cannot respond to ADH.

Question 18

Renal countercurrent multiplier
(a) serves to maintain a concentrated renal medulla
(b) anatomical structures are the loop of Henle
(c) involves reabsorption of sodium chloride in the descending limb
(d) is not very important in urine concentration in the kidneys
(e) involves water reabsorption in the ascending limb

Answer 18

Both of these answers are correct:
(a) serves to maintain a concentrated renal medulla
(b) anatomical structures are the loop of Henle

Question 19

The vasa recta ________.
(a) are tubules for water reabsorption
(b) are permeable to water but not solute
(c) are permeable to both water and solute
(d) are part of the renal countercurrent multiplier
(e) are also known as juxtamedullary nephrons

Answer 19

(c) are permeable to both water and solute

Explanation:
(a) Are tubules for water reabsorption: This statement is false. The vasa recta are not tubules; they are capillaries that surround the loop of Henle in the kidneys.

(b) Are permeable to water but not solute: This statement is false. The vasa recta are permeable to both water and solutes, allowing for the exchange of substances with the interstitial fluid.

(c) Are permeable to both water and solute: This statement is true. The vasa recta are permeable to both water and solutes, facilitating the countercurrent exchange mechanism that helps maintain the osmotic gradient in the renal medulla.

(d) Are part of the renal countercurrent multiplier: This statement is false. The vasa recta are part of the countercurrent exchange system, not the countercurrent multiplier. The countercurrent multiplier involves the loop of Henle.

(e) Are also known as juxtamedullary nephrons: This statement is false. Juxtamedullary nephrons are a type of nephron located near the medulla of the kidney, while the vasa recta are the capillary network associated with these nephrons.