Chapter 19 Human Physiology

Human Physiology: An Integrated Approach, 6e (Silverthorn)

Chapter 19 The Kidneys

1) Functions of the kidneys include all but one of the following. Identify the exception.

A) regulation of extracellular fluid volume

B) maintenance of ion balance in body fluids

C) regulation of blood protein levels

D) regulation of blood osmolarity

E) homeostatic regulation of blood pH

: C

Section Title: Functions of the Kidneys

Learning Outcome: 19.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

2) Ions directly regulated by the kidney include all EXCEPT which of the following?

A) Na+

B) K+

C) Ca2+

D) HCO3-

E) OH-

: E

Section Title: Functions of the Kidneys

Learning Outcome: 19.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

3) The characteristic yellow color of urine is attributed to the presence of

A) urobilinogen.

B) uric acid.

C) urea.

D) renin.

E) bile.

: A

Section Title: Functions of the Kidneys

Learning Outcome: 19.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

4) Urine is produced by the

A) gallbladder.

B) urinary bladder.

C) kidney.

D) ureter.

E) urethra.

: C

Section Title: Functions of the Kidneys

Learning Outcome: 19.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

5) Urine is carried to the urinary bladder by

A) blood vessels.

B) lymphatics.

C) the ureters.

D) the urethra.

E) All of the answers are correct.

: C

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.2

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

6) Technically, the kidneys are located

A) in the thoracic cavity.

B) in the abdominal cavity.

C) behind the pleural membranes.

D) behind the peritoneal membrane.

E) in the pelvic cavity.

: D

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.6

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

7) Blood flow through the kidney includes a feature seen in only a few organs. What is it?

A) portal system

B) arterial shunts

C) vascular sinuses

D) veins containing highly oxygenated blood

E) anastomoses

: A

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.3

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

8) Which structure is NOT part of the blood circulation through the kidney?

A) vasa recta

B) loop of Henle

C) glomerulus

D) renal corpuscle

: B

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.3

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

9) Which statement is NOT true?

A) The blood supply to the kidneys comes through the renal arteries.

B) As much as one fourth of the cardiac output may flow to the kidneys at any given moment.

C) The kidneys do not reabsorb filtered waste products.

D) The urinary bladder is filled by two ducts, called ureters, and emptied by the single urethra.

E) Women are more likely to develop urinary tract infections than men.

: C

Section Title: Overview of Kidney Function

Learning Outcome: 19.5

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

10) The Bowman's capsule and glomerulus make up the

A) renal pyramid.

B) loop of Henle.

C) renal corpuscle.

D) renal papilla.

E) collecting system.

: C

Section Title: Filtration

Learning Outcome: 19.4

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

11) Which of the following kidney processes is always active and always requires energy to occur?

A) filtration

B) reabsorption

C) secretion

D) excretion

: C

Section Title: Overview of Kidney Function

Learning Outcome: 19.5

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

12) A glomerulus is

A) the expanded end of a nephron.

B) a "knot" of capillaries that lies within the Bowman's capsule.

C) the portion of the nephron closest to the renal corpuscle.

D) the portion of the nephron that attaches to the collecting duct.

E) the hairpin-shaped segment of the nephron.

: B

Section Title: Overview of Kidney Function

Learning Outcome: 19.3

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

13) The portion of the nephron closest to the renal corpuscle is the

A) loop of Henle.

B) proximal tubule.

C) distal tubule.

D) collecting duct.

E) minor calyx.

: B

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.2

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

14) The portion of the nephron that attaches to the collecting duct is the

A) loop of Henle.

B) proximal tubule.

C) distal tubule.

D) collecting duct.

E) minor calyx.

: C

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.2

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

15) The hairpin-shaped segment of the nephron is the

A) loop of Henle.

B) proximal tubule.

C) distal tubule.

D) vasa recta.

E) minor calyx.

: A

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.2

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

16) The segment of the nephron between the proximal and distal tubules that loops down into the medulla of the kidney and returns back to the cortex is called the ________.

A) loop of Henle

B) Bowman's capsule

C) collecting duct

D) vasa recta

E) minor calyx

: A

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.2

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

17) The process of filtration in the kidney is most accurately described as

A) highly specific.

B) completely nonspecific.

C) relatively nonspecific.

: C

Section Title: Filtration

Learning Outcome: 19.5

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

18) All of the following will normally be found in the filtrate EXCEPT

A) glucose

B) potassium

C) erythrocytes

D) urobilinogen

: C

Section Title: Filtration

Learning Outcome: 19.5

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

19) Cysts on the kidney can press upon nephrons, raising the pressure inside the nephrons. How will this affect glomerular filtration rate and blood pressure?

A) GFR increases and blood pressure increases

B) GFR increases and blood pressure decreases

C) GFR decreases and blood pressure increases

D) GFR decreases and blood pressure decreases

: C

Section Title: Filtration

Learning Outcome: 19.10

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

20) The amount of plasma that filters into the nephrons is approximately ________ of the total volume.

A) 4/5

B) 1/5

C) 3/4

D) 1/2

E) 90%

: B

Section Title: Filtration

Learning Outcome: 19.3

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

21) In normal kidneys, blood cells and plasma proteins are

A) filtered then reabsorbed.

B) secreted then reabsorbed.

C) not filtered.

D) filtered and secreted.

: C

Section Title: Filtration

Learning Outcome: 19.3

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

22) Which is NOT a kidney filtration barrier?

A) glomerular capillary endothelium

B) basal lamina

C) Bowman's capsule epithelium

D) juxtaglomerular apparatus

: D

Section Title: Filtration

Learning Outcome: 19.7

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

23) The force for glomerular filtration is the

A) blood pressure in the glomerular capillaries.

B) osmotic pressure in the glomerular capillaries.

C) fluid pressure produced by the displacement of the fluid in the lumen of the tubules.

D) ATP-dependent processes in the nephron.

E) None of the answers are correct.

: A

Section Title: Filtration

Learning Outcome: 19.8

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

24) The primary function of the proximal tubule is

A) filtration.

B) reabsorption of ions, organic molecules, and water.

C) secretion of acids and ammonia.

D) secretion of drugs.

E) adjusting the urine volume.

: B

Section Title: Reabsorption

Learning Outcome: 19.5

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

25) Contents in the peritubular capillaries are actively transported into proximal and distal convoluted tubules in a process known as:

A) excretion

B) filtration

C) reabsorption

D) secretion

: D

Section Title: Overview of Kidney Function

Learning Outcome: 19.5

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

26) Glucose and amino acids are reabsorbed by

A) diffusion.

B) symport with sodium.

C) cotransport.

D) countertransport.

: B

Section Title: Reabsorption

Learning Outcome: 19.11

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

27) Which of the following statements about autoregulation is NOT true?

A) Myogenic response is the intrinsic ability of vascular smooth muscle to respond to pressure changes.

B) Myogenic response is a paracrine signaling mechanism.

C) In tubuloglomerular feedback, stretch-sensitive ion channels open, resulting in depolarization of smooth muscle cells.

D) In myogenic response, the macula densa cells send a paracrine message to the neighboring afferent arteriole.

: A

Section Title: Filtration

Learning Outcome: 19.10

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

Match each step in urine formation to its description.

A. excretion

B. filtration

C. reabsorption

D. secretion

28) movement from the nephron lumen to the external environment

: A

Section Title: Overview of Kidney Function

Learning Outcome: 19.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

29) movement from the nephron lumen to the blood

: C

Section Title: Overview of Kidney Function

Learning Outcome: 19.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

30) movement from the glomerulus to the nephron lumen

: B

Section Title: Overview of Kidney Function

Learning Outcome: 19.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

31) movement from the peritubular capillaries to the nephron lumen

: D

Section Title: Overview of Kidney Function

Learning Outcome: 19.1

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

Match each substance with its primary mode of transport across the kidney epithelium.

A. transcytosis

B. active transport

C. symport with a cation

D. passive reabsorption/diffusion

32) sodium

: B

Section Title: Reabsorption

Learning Outcome: 19.11

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

33) glucose

: C

Section Title: Reabsorption

Learning Outcome: 19.11

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

34) urea

: D

Section Title: Reabsorption

Learning Outcome: 19.11

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

35) small plasma proteins

: A

Section Title: Reabsorption

Learning Outcome: 19.11

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

36) After it is formed, urine is temporarily stored in the ________.

: urinary bladder

Section Title: Micturition

Learning Outcome: 19.2

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

37) Urine is carried to the external environment by the ________.

: urethra

Section Title: Micturition

Learning Outcome: 19.2

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

38) The plasma concentration at which all of the renal carriers for a given substance are saturated is the ________.

: renal threshold

Section Title: Reabsorption

Learning Outcome: 19.12

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

39) The amount of filtrate entering the proximal tubules of the kidneys each minute is the ________.

: GFR or glomerular filtration rate

Section Title: Filtration

Learning Outcome: 19.9

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

40) The percentage of total plasma volume that filters is called the ________.

: filtration fraction

Section Title: Filtration

Learning Outcome: 19.9

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

41) When fluid flow through the distal tubule increases as a result of increased GFR, the macula densa cells send a chemical message to the neighboring afferent arteriole. The afferent arteriole constricts, increasing resistance and decreasing GFR. This type of autoregulation involving both the kidney tubule and the arteriole is known as ________.

: tubuloglomerular feedback

Section Title: Filtration

Learning Outcome: 19.10

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

42) The ________ branch off the ________ and supply blood to the kidneys.

: renal arteries, abdominal aorta

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.3

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

43) The ________ carry blood from the kidneys back to the ________.

: renal veins, inferior vena cava

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.3

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

44) Eighty percent of the nephrons in a kidney are contained within the ________, but the other 20%, called the ________ nephrons, dip down into the ________.

: cortex, juxtamedullary, medulla

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.4

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

45) The ________ are the long peritubular capillaries that dip into the medulla.

: vasa recta

Section Title: Overview of Kidney Function

Learning Outcome: 19.4

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

46) The nephron begins with a hollow, ball-like structure called ________.

: Bowman's capsule

Section Title: Overview of Kidney Function

Learning Outcome: 19.2

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

47) The ________ lie between and around the glomerular capillaries.

: mesangial cells

Section Title: Filtration

Learning Outcome: 19.4

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

48) The specialized cells found in the capsule epithelium are called ________. These cells have long cytoplasmic extensions called ________.

: podocytes; foot processes

Section Title: Filtration

Learning Outcome: 19.4

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

49) Neural control of GFR is mediated by ________ that innervate ________ receptors on vascular smooth muscle causing ________.

: sympathetic neurons, alpha, vasoconstriction

Section Title: Filtration

Learning Outcome: 19.10

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Comprehension)

50) The excretion of glucose in the urine is called ________.

: glucosuria or glycosuria

Section Title: Reabsorption

Learning Outcome: 19.12

: Level I: Reviewing Facts and Terms (Bloom's Taxonomy: Knowledge)

51) Place the following blood vessels that carry blood to and within the kidney in the order in which blood passes through them.

1. afferent arteriole

2. efferent arteriole

3. glomerulus

4. peritubular capillary

A) 4, 2, 3, 1

B) 1, 3, 2, 4

C) 4, 3, 2, 1

D) 1, 2, 3, 4

E) 3, 4, 2, 1

: B

Section Title: Overview of Kidney Function

Learning Outcome: 19.4

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

52) When the plasma concentration of a substance exceeds its renal concentration, more of the substance will be

A) filtered.

B) reabsorbed.

C) secreted.

D) excreted.

E) None of the answers are correct.

: D

Section Title: Reabsorption

Learning Outcome: 19.15

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

53) Damage to the renal medulla would interfere first with the functioning of the

A) Bowman's capsule.

B) distal tubule.

C) collecting ducts.

D) proximal tubule.

E) glomerulus.

: C

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.2

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

54) An obstruction in a glomerulus would affect the flow of blood into the

A) renal artery.

B) efferent arteriole.

C) afferent arteriole.

D) renal vein.

: B

Section Title: Anatomy of the Urinary System

Learning Outcome: 19.2

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

55) If blood flow through the afferent arterioles increases,

A) stretch reflexes trigger vasoconstriction to reduce the flow.

B) the smooth muscle in the vessel walls stretches to accommodate the increased flow.

C) the stretch triggers further relaxation of the arteriolar wall, lessening blood pressure.

D) the smooth muscle in the vessel walls stretches to accommodate the increased flow and the stretch triggers further relaxation of the arteriolar wall, lessening blood pressure.

: A

Section Title: Filtration

Learning Outcome: 19.10

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

56) Urea is

A) actively secreted in the distal tubule.

B) actively reabsorbed in the proximal tubule.

C) passively reabsorbed in the proximal tubule.

D) completely eliminated in the urine.

E) actively transported into the filtrate by the cells of the collecting duct.

: C

Section Title: Reabsorption

Learning Outcome: 19.5

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

57) In the lumen of the proximal tubule, Na+ concentration ________ the Na+ concentration inside the cells of the tubule wall.

A) is much higher than

B) is slightly higher than

C) is about the same as

D) is slightly lower than

E) is much lower than

: A

Section Title: Reabsorption

Learning Outcome: 19.6

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

58) The typical pattern for molecules absorbed by Na+-dependent transport involves this: an apical ________ and a basolateral ________.

A) facilitated diffusion carrier, osmotic gradient

B) symport protein, facilitated diffusion carrier

C) symport protein, osmotic gradient

D) osmotic gradient, symport protein

E) facilitated diffusion carrier, symport protein

: B

Section Title: Reabsorption

Learning Outcome: 19.5

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

59) One substance has no membrane transporters to move it but can diffuse freely through open leak channels if there is a concentration gradient. Initially, this substance's concentrations in the filtrate and extracellular fluid are equal. Later, however, the active transport of Na+ and other solutes creates a gradient by removing water from the lumen of the tubule where it is located. What substance is this?

A) glucose

B) calcium

C) urea

D) glucose and calcium

E) glucose, calcium, and urea

: C

Section Title: Reabsorption

Learning Outcome: 19.5

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

60) Measurements in a nephron reveal a glomerular hydraulic pressure of 69 mm Hg, and a fluid pressure in the Bowman's capsule of 15 mm Hg. Assuming that the plasma osmotic pressure is 30 mm Hg, and that essentially no plasma proteins are filtered by the glomerulus, what is the net glomerular filtration pressure in this case?

A) -6 mm Hg

B) 24 mm Hg

C) 54 mm Hg

D) 84 mm Hg

E) 114 mm Hg

: B

Section Title: Filtration

Learning Outcome: 19.8

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

61) In a normal kidney, which of the following conditions would cause an increase in the glomerular filtration rate (GFR)?

A) constriction of the afferent arteriole

B) a decrease in the hydraulic pressure of the glomerulus

C) an increase in the capsular hydraulic pressure

D) a decrease in the concentration of plasma proteins in the blood

E) a decrease in the net glomerular filtration pressure

: D

Section Title: Filtration

Learning Outcome: 19.8

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

62) A person with cirrhosis of the liver has lower than normal levels of plasma proteins and a higher than normal GFR. Explain why a decrease in plasma protein concentration would cause an increase in GFR.

: The primary driving force for GFR is blood pressure, opposed by fluid pressure in Bowman's capsule and osmotic pressure due to plasma proteins. If a person has fewer plasma proteins due to liver disease, the plasma will have a lower osmotic pressure. With less osmotic pressure opposing the GFR, GFR will increase.

Section Title: Filtration

Learning Outcome: 19.8

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

63) Patrick's urine sample reveals a high concentration of glucose. Is glucose normally present in urine? Suggest two possible mechanisms to explain why the kidney would excrete excess glucose, and what abnormality may underlie those conditions.

: Glucose transporters may be saturated, preventing complete reabsorption of glucose (filtration exceeds reabsorption). This can happen with extremely high glucose ingestion or with untreated diabetes mellitus. A genetic defect resulting in an insufficient number of glucose transporters is another possibility.

Section Title: Reabsorption

Learning Outcome: 19.12

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

64) Trace a drop of water through the urinary system, beginning with the plasma in the renal artery.

: Plasma in the renal artery flows into smaller branches, entering the arcuate arteries, which lead to the afferent arterioles, which in turn lead to the glomeruli. Water moves from glomeruli into the nephrons (PCT, loop of Henle, then DCT), into the collecting ducts, then renal calyces and into the renal pelvis, passes into a ureter, then to the urinary bladder; finally, it is expelled as urine through the urethra.

Section Title: Overview of Kidney Function

Learning Outcome: 19.2

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

65) List and describe the three filtration barriers that substances leaving the plasma must pass through before entering the tubule lumen.

:

1. the glomerular capillary endothelium

2. a basal lamina

3. the epithelium of Bowman's capsule

See the "The Renal Corpuscle Contains Three Filtration Barriers" section of the chapter.

Section Title: Filtration

Learning Outcome: 19.7

: Level II: Reviewing Concepts (Bloom's Taxonomy: Comprehension)

66) List and summarize the forces that influence filtration across the walls of glomerular capillaries.

:

1. hydrostatic pressure

2. colloid osmotic pressure

3. hydrostatic fluid pressure

See the "Filtration Occurs Because of Hydrostatic Pressure in Capillaries" section of the chapter.

Section Title: Filtration

Learning Outcome: 19.8

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

67) Reabsorption involves what two methods of transport? Describe each. What determines which route a solute will take?

:

1. transepithelial transport: substances cross both apical and basolateral membranes of the tubule epithelial cell.

2. paracellular pathway: substances pass through the junction between two adjacent cells.

The permeability of the epithelial junction and the electrochemical gradient for the solute determines which route it will take.

Section Title: Reabsorption

Learning Outcome: 19.11

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

68) Describe GFR autoregulation, and explain why it is important.

:

1. The myogenic response is the ability of the vascular smooth muscle to constrict or dilate to keep pressure and flow constant, thereby keeping GFR constant. Vasoconstriction is more effective at this than vasodilation.

2. Tubuloglomerular feedback involves production of a paracrine, in response to increased GFR, which constricts the afferent arteriole to decrease GFR. Autoregulation helps protect the filtration barriers from high blood pressures that could damage them.

Section Title: Filtration

Learning Outcome: 19.10

: Level II: Reviewing Concepts (Bloom's Taxonomy: Application)

69) Ruby is 77 years old and can no longer control her urination. What changed in the reflex pathway that used to control her urination?

: Micturition normally occurs when stretch receptors in the bladder wall are stimulated by distension due to the accumulation of urine. The stretch receptors project to an integration center in the spinal cord, which stimulates parasympathetic neurons of the bladder wall, which stimulates bladder contraction, forcing the internal urethral sphincter to open. At the same time, the spinal control center inhibits somatic motor neurons that control the external urethral sphincter, which relaxes in response, so that urine can flow out. The spinal reflex is normally overridden by descending control from the brain stem and cerebral cortex. The brain inhibits the parasympathetic output to the bladder and stimulates the somatic motor output to the external urethral sphincter, thus preventing urination until a convenient time. It is likely that Ruby's descending control is what is no longer working properly; thus she is not able to suppress the urge until she can get to a toilet.

Section Title: Micturition

Learning Outcome: 19.16

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

70) Sylvia is suffering from severe edema in her arms and legs. Her physician prescribes a diuretic (a substance that will increase the volume of urine produced). Why might this help to alleviate Sylvia's problem?

: One simple answer is that a diuretic reduces the free fluid in the body. A more complex explanation is that increasing the volume of urine produced would decrease the total blood volume of the body. This in turn would lead to a decreased blood hydraulic pressure. Edema is frequently the result of hydraulic pressure of the blood exceeding the opposing forces at the capillaries in the affected area. Depending on the actual cause of the edema, decreasing the blood hydraulic pressure would decrease edema formation and possibly cause some of the fluid to move from the interstitial space back to the blood. Diuresis would also increase the concentration of the proteins in the plasma, contributing to the fluid's movement out of the tissues and into the blood.

Section Title: Overview of Kidney Function

Learning Outcome: 19.8

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

71) Make a map of the following terms: blood, Bowman's capsule, collecting duct, distal tubule, excretion, external environment, filtration, loop of Henle, lumen, osmosis, peritubular capillaries, proximal tubule, urine, water. Add terms as needed.

: Maps will vary. See Figure 19.2 and the "Overview of Kidney Function" section of the chapter.

Section Title: Overview of Kidney Function

Learning Outcome: 19.3

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

72) A professor gave the following analogy of kidney function to his freshman biology class: "Imagine your desk is a disorganized mess, containing things worth keeping and things you should throw out. Instead of picking through each item one by one and considering if it is to keep or toss, you sweep your arm across your desktop in one smooth motion, knocking the entire contents of the desk into your large trash can. Then you pull the items you want to keep out of the trash can and place them back on your desk." In what ways is this analogy accurate? In what ways is it inaccurate? Some students in his class argue that the kidneys are inefficient and poorly designed. How should the professor respond? What modern medical device may he cite in his response?

: His analogy is accurate in that the glomerulus does dump contents into the nephron that the body needs and will take back. His analogy is inaccurate in that the entire contents of the plasma are not dumped, rather about 1/5 of the volume enters the nephron. While one could easily imagine a more efficient way to remove waste from the blood, the kidneys can only use the tools they have, namely various membrane transport processes and the physical laws governing movement of water and solutes. Kidney dialysis machines rely on diffusion through semipermeable membranes, mimicking part of normal kidney function.

Section Title: Overview of Kidney Function

Learning Outcome: 19.5

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

73) Presence of glucose in the urine is evidence of what condition?

: Diabetes mellitus

Section Title: Overview of Kidney Function

Learning Outcome: 19.12

: Level III: Problem Solving (Bloom's Taxonomy: Synthesis)

74) Fred weighs 100 kg. Assume his total blood volume is 7%, his heart pumps his total blood volume within 90 seconds, and his renal blood flow is 20% of his cardiac output. Calculate the volume of blood that flows through Fred's kidneys each minute.

: Fred's blood volume = 100 kg × 0.07 = 7 L = 7000 mL. At least two thirds of this volume must circulate per minute = 7000 mL × 0.67 = 4690 mL/min minimum cardiac output (CO); values up to 5000 mL/min would still be within a normal range; 4690 × 20% = 938 mL/min; 5000 × 20% = 1000 mL/min, thus blood flow to Fred's kidneys approximates 938-1000 ml/min.

Section Title: Filtration

Learning Outcome: 19.9

: Level IV: Quantitative Problems (Bloom's Taxonomy: Application)

75) You are a physiologist on a space flight to a distant planet. You discover intelligent humanoid aliens inhabiting the planet, and they willingly submit to your tests. You discover that the alien's kidney handles the sugar alcohol mannitol just like our kidneys handle inulin. You also test the alien for its renal handling of glucose. The data from that experiment are: Plasma level (constant over 24 hrs): 6 g/dL of mannitol and 2 g/dL of glucose; 24 hr. urine sample: volume of 2 L, containing 144 g mannitol and 52 g glucose.

A. What is the alien's glomerular filtration rate?

B. What is the alien's clearance rate for glucose?

C. How does the alien kidney handle glucose?

: Human kidneys filter inulin, a polysaccharide from dahlia roots, but do not reabsorb or secrete it. Thus, 100% of the inulin in a urine sample is filtered inulin. For this reason, the inulin excretion rate is the same as the glomerular filtration rate.

A. The alien's GFR = excretion rate of mannitol/plasma concentration of mannitol

= 144 g/day × 1 dL/6 g × 0.1 L/1 dL = 2.4 L/day.

B. Using 2.4 L/day as GFR, the filtered load for glucose = plasma concentration of glucose × GFR

= 2 g/dL × 2.4 L/day × 1 dL/0.1 L = 48 g glucose.

C. There were 52 g of glucose produced in 24 hours. Since the clearance of glucose is greater than the filtered load, some glucose must have been secreted. Therefore the alien's kidney filters and secretes glucose.

Section Title: Filtration

Learning Outcome: 19.14

: Level IV: Quantitative Problems (Bloom's Taxonomy: Application)

76) A man's leg was crushed between a car bumper and a wall. His physicians believe their patient has suffered kidney damage from myoglobin blocking glomerular pores. Tests showed the following results:

plasma creatinine: 30 mg/100 mL plasma

24 hour urine specimen: volume = 1 liter

urine creatinine 30 mg/mL urine

A. How many mg of creatinine are in the urine specimen? How much creatinine appears in the urine per hour?

B. What is the patient's creatinine clearance in mL/min?

C. What is the patient's GFR?

D. Is this a normal GFR? Did the patient sustain kidney damage?

:

A. 1000 mL urine × 30 mg creatinine/mL urine = 30,000 mg creatinine in the specimen.

30,000 mg/24 hr = 1250 mg creatinine.

B. Creatinine clearance = excretion rate of creatinine/plasma concentration creatinine.

clearance = 1250 mg creatinine/hr × 1 hr/60 min/30 mg creatinine/100 mL plasma

= 20.8 mg creatinine/min/0.3 mg creatinine/mL plasma

= 69.4 mL plasma/min

C. GFR approximately equal to clearance rate for creatinine, or approximately 70 mL/min.

D. A more typical value for GFR is 125 mL/min, so 70 mL/min represents a severe decline. Thus, kidney damage has most likely occurred.

Section Title: Filtration

Learning Outcome: 19.14

: Level IV: Quantitative Problems (Bloom's Taxonomy: Application)