mod 8 Urinary Tract and renal physiology

Question 1

• 2b. The kidneys are retroperitoneal – what does this mean?

Answer 1

• The retroperitoneum is the part of the abdominal cavity which lies
between the posterior parietal peritoneum and anterior to the
transversalis fascia
• Organs are retroperitoneal if they have peritoneum on their anterior
side only

Question 2

. Describe the micturition reflex

Answer 2

• When the bladder volume reaches about
400mL (in an adult), the urge to void
becomes so great that micturition can no
longer be delayed
• Visceral afferent impulses from the bladder
wall receptors act via spinal interneurons to
excite parasympathetic neurons and inhibit
sympathetic and somatic neurons
• Three simultaneous events
1. Contraction of detrusor muscle by activation
of parasympathetic fibres and inhibition of
sympathetic fibres
2. Relaxation and opening of internal urethral
sphincter by activation of parasympathetic
fibres and inhibition of sympathetic fibres
3. Relaxation and opening of external urethral
sphincter by inhibition of the somatic
efferents
Bladder contracts and internal and external
sphincters open  voiding of urine

Question 3

• 5. In terms of body water compartments, which contains the greatest
percentage of body water?
• A. plasma
• B. tissue fluid (extracellular interstitial fluid)
• C. intracellular fluid
• D. the abdominal cavity
• E. whole blood

Answer 3

• C. intracellular fluid

Question 4

• 6. The apex of the renal pyramid is called the
• A. major calyx
• B. minor calyx
• C. renal papilla
• D. renal pelvis
• E. ureter

Answer 4

• C. renal papilla

Question 5

• 7. The renal pyramid is
• A. the innermost layer of kidney tissue
• B. the conical shaped structure in the renal medulla
• C. an internal cavity lined by the fibrous capsule and located in the
area of the hilus
• D. a large branch of the renal pelvis
• E. a knot of capillaries in the renal corpuscle

Answer 5

• B. the conical shaped structure in the renal medulla

Question 6

• 8. Which of the following is correct concerning the
location of the kidneys?
• A. the right kidney is usually higher than the left one
• B. they are both located behind the parietal
peritoneum
• C. their upper borders are about at the level of the
third lumbar vertebra
• D. They are against the anterior wall of the abdominal
cavity
• E. none of the above

Answer 6

• B. they are both located behind the parietal

peritoneum

Question 7

9. Major calyces are
   • A. large branches of the renal pelvis
   • B. expanded ends of nephrons
   • C. basic functional layers of the kidney
   • D. conical-shaped structures in the renal medulla
   • E. the expanded ends of renal pyramids

Answer 7

A. large branches of the renal pelvis

Question 8

• 10. The thirst centre is located in the
• A. thalamus
• B. hypothalamus
• C. midbrain
• D. pons
• E. medulla oblongata

Answer 8

• B. hypothalamus

Question 9

11. The external urethral sphincter is formed by
    • A. smooth muscle in the wall of the bladder
    • B. smooth muscle in the wall of the urethra
    • C. skeletal muscle of the urogenital diaphragm
    • D. skeletal muscle in the wall of the bladder
    • E. smooth and skeletal muscle in the wall of the
    bladder

Answer 9

• D. skeletal muscle in the wall of the bladder

Question 10

12. Which of the following statements concerning the
    micturition reflex is false?
    • A. relaxation of the external sphincter occurs under
    voluntary control
    • B. interneurons in the spinal cord relay sensory
    information to the cerebral cortex
    • C. increased afferent impulses from stretch receptors
    in the urinary bladder facilitate parasympathetic motor
    neurons in the spinal cord
    • D. the internal sphincter relaxes when the external
    sphincter is relaxed
    • E. the micturition reflex is controlled by neurons in the
    lumbar region of the spinal cord

Answer 10

• E. the micturition reflex is controlled by neurons in the
lumbar region of the spinal cord ( neurons in the
sacral region of the spinal cord are involved)

Question 11

• 13. Which of the following correctly lists the order of
structures through which urine flows after its
formation in the nephron?
• A. calyx, renal pelvis, ureter, urinary bladder, urethra
• B. renal pelvis, calyx, ureter, urinary bladder, urethra
• C. renal pelvis, calyx, urethra, ureter, urinary bladder
• D. renal pelvis, calyx, urinary bladder, ureter, urethra
• E. glomerular capsule, PCT, nephron loop (LoH), DCT,
collecting duct

Answer 11

• A. calyx, renal pelvis, ureter, urinary bladder, urethra

Question 12

• 14. The detrusor muscle
• A. moves urine through the ureters
• B. compresses the urinary bladder and expels urine through the
urethra
• C. functions as the internal urinary sphincter
• D. functions as the external urinary sphincter
• E. is located in the renal pelvis

Answer 12

B. compresses the urinary bladder and expels urine through the
urethra

Question 13

• 15. The micturition reflex is voluntarily controlled by
the
• A. person controlling contraction and relaxation of the
pyloric sphincter valve
• B. sympathetic impulses stimulating the internal
urethral sphincter valve
• C. cerebral cortex stimulating or inhibiting the
external urethral sphincter valve
• D. voluntary contractions of inhibition of the prostate
gland
• E. spinal cord

Answer 13

C. cerebral cortex stimulating or inhibiting the

external urethral sphincter valve

Question 14

• 16. Define detrusor muscle

Answer 14

• Smooth muscle wall of the urinary bladder
• When relaxed allows urine storage
• Contraction compresses the bladder contents and expels urine from
the bladder

Question 15

• 17. Distinguish between the internal and external urethral sphincters

Answer 15

• The internal sphincter is a smooth muscle ring and is
continuous with the detrusor muscle
• Under autonomic control by the sympathetic and
parasympathetic systems
• Sympathetic activation contraction urine storage
• Parasympathetic activation relaxation and
micturition
• The external sphincter is part of the urogenital
diaphragm
• Composed of skeletal muscle
• Voluntary (somatic motor) control
• Contraction  allows urine storage
• Relaxation allows micturition

Question 16

• 1. Which of the following represents the correct order
of anatomical structures in the nephron?
• A. glomerulus, proximal convoluted tubules (PCTs),
loop of Henle (LoH), distal convoluted tubules (DCTs)
• B. PCTs, LoH, DCTs, glomerulus
• C. glomerulus, DCTs, LoH, PCTs
• D. DCTs, glomerulus, PCTs, LoH
• E. glomerulus, LoH, PCTs, DCTS

Answer 16

• A. glomerulus, proximal convoluted tubules (PCTs),

loop of Henle (LoH), distal convoluted tubules (DCTs)

Question 17

• 2) Which structure(s) are responsible for collecting the primary
filtrate as it is formed?
• a) the proximal tubules
• b) the bladder
• c) the glomerulus
• d) the Bowman’s capsules
• e) the collecting ducts

Answer 17

d) the Bowman’s capsules (glomerular capsules)

Question 18

• 3) The Tmax for glucose in the renal tubules is
approximately 300mg/100ml of filtrate.
• What does this mean?
• a) any value lower than this will likely ensure no
glucose is found in urine
• b) any value higher than this will likely ensure no
glucose is found in urine
• c) any value lower than this will likely cause glucose
to be left in urine
• d) any value higher than this will likely cause glucose
to be left in urine
• e) options a) and d) are both correct

Answer 18

e) options a) and d) are both correct

Question 19

4. What would you not expect to find in the primary
filtrate?
• a) glucose
• b) urea
• c) haemoglobin
• d) albumin
• e) neither c) or d)

Answer 19

• e) neither c) or d)

Question 20

5) What is the net filtration pressure, assuming that:
(all values in mmHg)
• 1. glomerular capillary hydrostatic pressure = 54
• 2. plasma COP = 32
• 3. hydrostatic pressure in Bowman’s capsule = 14
• a) 54 mmHg
• b) 32 mmHg
• c) 22 mmHg
• d) 14 mmHg
• e) 8 mmHg

Answer 20

• Forces driving water and solutes out of plasma in
glomerular capillaries through filtration membrane into
Bowman’s (glomerular)capsule:
• Glomerular hydrostatic pressure (HPgc) = glomerular
blood pressure
• Bowman’s capsule osmotic pressure (OPcs): healthy
urine has negligible protein, so that OP in Bowman’s
capsule ≈0
• Forces opposing movement of water and solutes from
the glomerular capillaries into Bowman’s capsule:
• Colloid osmotic (oncotic) pressure of blood in the
glomerular capillaries (OPgc)
• Capsular hydrostatic pressure (HPcs) exerted by fluid in
Bowman’s capsule
• NFP = (HPgc+ OPcs)-(HPcs+ OPgc)
• Where HPgc = glomerular blood hydrostatic pressure
• OPgc = blood colloid osmotic (oncotic) pressure
• HPcs = capsular hydrostatic pressure
• Opcs = osmotic pressure of fluid in Bowman’s capsule
• NFP = (54 + 0)– (32 + 14)mmHg
• = 54 – 46 mmHg
• = 8 mmHg

Question 21

• 6) Presuming the same as the previous question but
informed that filtrate COP is 1 mmHg, what would net
pressure now be?
• a) 33 mmHg
• b) 9 mmHg
• c) 7 mmHg
• d) 13 mmHg
• e) 39 mmHg

Answer 21

• b) 9 mmHg
• NFP = (HPgc+ OPcs)-(HPcs+ OPgc)
• = (54 + 1)– (32 + 14)mmHg
• = 55 – 46 mmHg
• = 9 mmHg

Question 22

• 7) How much of filtered water is absorbed in the
proximal tubule (known as “obligatory” reuptake)
• a) ~25%
• b) ~50%
• c) ~65%
• d) ~ 95%
• e) option a) would be correct if the term
“facultative” was used in place of “obligatory” since
the uptake in the proximal tubule is facultative

Answer 22

• c) ~65%

Question 23

• 8) The renal juxtaglomerular apparatus: what do
macula densa cells do?
• a) release renin
• b) release angiotensin
• c) release factors which constrict or dilate the
associated afferent arterioles
• d) ensure that associated efferent arterioles are
normally severely constricted (i.e. essentially closed)
• e) induce leakiness in glomerular capillaries

Answer 23

c) release factors which constrict or dilate the

associated afferent arterioles

Question 24

13. Most filtered water is reabsorbed in the kidney:
    which segment of a nephron achieves the bulk of this
    reabsorption, and how is this achieved?

Answer 24

• ~65% of filtered water is reabsorbed in the PCT

* Water follows sodium by osmosis

Question 25

• 14. Diabetes mellitus refers to the production of sweet urine – explain
how and why this occurs.
• What other, related renal symptom occurs with respect to urine
formation?

Answer 25

• Saturation of the Na+-Glucose transporters in the
proximal convoluted tubule i.e. Tm is exceeded
• By leaving glucose in the urine it exerts an osmotic
pull on water, holding more water in the tubule
system
• Uncontrolled DM patients produce large volumes of
“sweet” urine (diuresis)

Question 26

• 15. The kidneys can excrete a very dilute urine or a comparatively
concentrated urine – give figures in mOsm to these extremes, and
describe how each is arrived at.

Answer 26

• Establishment and maintenance of the osmotic
medullary gradient
• and
• The action of ADH

Question 27

• 19.	The	kidneys	activate	or	produce	all	but	one	of	the	following		–
which	is	the	odd	one	out?
• a)	vit D	
• b)	erythropoietin	
• c)	antidiuretic	hormone	
• d)	renin
• e)	the	original	statement	is	incorrect	– the	kidneys	produce	or	
activate	all	of	the	above

Answer 27

• c) antidiuretic hormone

Question 28

20. Presuming that the transport maximum for glucose
    carriers in the proximal tubule of the kidney is
    300mg/100ml filtrate, what would happen if the
    filtrate contained 350 mg glucose/100ml
    • a) the excess glucose will be taken up the distal tubule,
    and urine volume will remain unchanged
    • b) excess glucose will be taken up the collecting duct
    and bladder, at the expense of water, meaning a
    hypotonic diuresis will occur
    • c) the excess glucose will remain in the urine, occupy
    space, and therefore reduce water loss, reducing the
    volume of urine lost
    • d) the excess glucose will remain in the urine, attract
    water osmotically, meaning a diuresis will occur

Answer 28

d) the excess glucose will remain in the urine, attract

water osmotically, meaning a diuresis will occur

Question 29

21. Approximately what maximum tissue osmolarity is
    created by the long loops of Henle, and it what tissue
    is this created?
    • a) ~120 mOsmols,……in the medulla
    • b) ~1200 mOsmols,……in the cortex
    • c) ~2100 mOsmols,……in both the cortex and medulla
    • d) ~1200 mOsmols,……in the medulla
    • e) ~ 300 mOsmols, ……in both the cortex and medulla

Answer 29

• d) ~1200 mOsmols,……in the medulla

Question 30

• 22. Why don’t we suddenly produce a large volume
of urine when our blood pressure rises during
exercise, for example?
• a) in fact we do, but the excess urine is reabsorbed
by the bladder
• b) the myogenic response reduces flow through the
afferent glomerular arteriole
• c) sodium pumps in the proximal tubule are inhibited
by high blood pressure
• d) sympathetic nerves reduce blood flow to the
kidneys
• e) both b) and d) can be involved

Answer 30

e) both b) and d) can be involved

Question 31

• 23. What is the role of angiotensin converting enzyme (ACE)
• a) to activate conversion of renin to angiotensin I
• b) to convert angiotensin I to angiotensin II
• c) to activate conversion of renin to angiotensin II
• d) to convert angiotensin I to renin
• e) to convert angiotensin II to aldosterone

Answer 31

• b) to convert angiotensin I to angiotensin II

Question 32

• 24. What stimulates the release of aldosterone?
• a) low plasma Na+
• b) drop in arterial BP
• c) high plasma K+
• d) angiotensin II
• e) all of the above

Answer 32

• e) all of the above

Question 33

25.	What	stimulates	release	of	renin?	
• a)	low	BP	
• b)	low	GFR	
• c)	sympathetic	activity	
• d)	all	of	the	above	
• e)	none	of	the	above,	renin	is	always	present	and	simply	needs	to	be	
activated

Answer 33

d) all of the above

Question 34

• 26. What specific properties of the renal vasa recta
facilitate it’s role in maintaining low [NaCl] in the
medulla
• a) slow moving blood
• b) the presence of a vascular loop that, essentially,
follows the loop of Henle
• c) high COP
• d) all of the above
• e) all of the above, but only if the original statement
stated that the vasa recta helped maintain high [NaCl]
in the medulla

Answer 34

• e) all of the above, but only if the original statement
stated that the vasa recta helped maintain high [NaCl]
in the medulla

Question 35

• 27. This hormone directly inhibits sodium and water retention by the
kidneys
• a) aldosterone
• b) renin
• c) atrial natriuretic peptide
• d) angiotensin
• e) options a) and b) both serve this function

Answer 35

• c) atrial natriuretic peptide

Question 36

• 28. Cells of the juxtaglomerular apparatus are in direct contact with….
• a) the proximal convoluted tubule
• b) the loop of Henle
• c) the collecting ducts
• d) the distal convoluted tubule
• e) the vasa recta

Answer 36

• d) the distal convoluted tubule