urinary

Question 1

List 5 different functions of the kidneys (5 marks).

Answer 1

• removal of wastes from blood
• regulation of blood volume
• regulation of plasma concentration of electrolytes
• regulation of plasma pH (excretion of H+)
• production of erythropoeitin
• conversion of vitamin D to active form

Question 2

List four nitrogenous wastes and describe the origin of each in metabolism (4
marks).

Answer 2

• urea from protein catabolism
• ammonia from protein catabolism
• creatinine from muscle metabolism or diet
• urobilinogen from blood degradation
• uric acid from nucleic acid degradation

Question 3

Name the three main processes that occur during the formation of urine and outline
where each occurs (3 marks).

Answer 3

• filtration occurs between the glomerulus and and the glomerular capsule
• reabsorption occurs in the proximal and distal convoluted tubules, loop of Henle and collecting duct
• secretion occurs in the proximal and distal convoluted tubules, loop of Henle and collecting duct

Question 4

The rate of flow of blood through the kidneys is normally about _____________ per minute

Answer 4

1 L

Question 5

5) The glomerular filtration rate is normally about ______________ per minute.

Answer 5

100 ml

Question 6

The rate of urine production by the kidneys is normally about __________ per
minute.

Answer 6

1ml

Question 7

List the three layers of the filtration membrane that a water molecule passes through
on its way from the blood to the glomerular filtrate.

Answer 7

1) simple squamous epithelium of lining of capillary of glomerulus
2) basement membrane
3) simple squamous epithelium of inner layer of glomerular capsule

Question 8

Explain why some molecules pass through the filtration membrane of the
glomerulus and some do not – give some examples of each kind.

Answer 8

• water and other small molecules pass through the pores in the filtration membrane
• large molecules, like most proteins, are too large to pass through the pores of the filtration membrane

Question 9

Describe the three major forces that are important in glomerular filtration and
explain how they act (2 marks).

Answer 9

1) blood pressure (~60 mm Hg) in the afferent arteriole is high and promotes filtration
2) capsule pressure results from the present of fluid in the glomerular capsule and inhibits filtration
3) osmotic pressure occurs because the concentration of proteins is greater in the plasma of the glomerulus than in the filtrate in the capsule and inhibits filtration

Question 10

Describe the mechanism for autoregulation in the glomerulus and how it influences
kidney function.

Answer 10

-afferent arterioles constrict in response to increased blood pressure and dilate in response to decreased blood pressure so as to maintain relatively a constant glomerular filtration rate even though systemic blood pressure changes

Question 11

Describe the effect of sympathetic stimulation on kidney function.

Answer 11

-activation of the sympathetic nervous system results in constriction of afferent arterioles and decreased glomerular filtration rate

Question 12

The renin-angiotensin system is activated in response to ___________________

Answer 12

decreased blood pressure

Question 13

List two actions of angiotensin

Answer 13

• constriction of most systemic blood vessels, resulting in increased blood pressure
• constriction of afferent arterioles, resulting in decreased glomerular filtration rate

Question 14

14) Angiotensin II is produced from _____________ in response to ______________

Answer 14

angiotensin I; angiotensin converting enzyme (ACE)

Question 15

Most of the water of the filtrate is reabsorbed by a region of the kidney tubule called
the __________________.

Answer 15

proximal convoluted tubule

Question 16

List 6 substances that are reabsorbed by the proximal tubule and describe the
mechanism by which each is reabsorbed (3 marks).

Answer 16

1) Na+ - active transport, together with another solute molecule
2) K+ - passive transport, because of concentration gradient
3) glucose - active transport, together with Na+
4) amino acids - active transport, along with Na+
5) bicarbonate-active transport, along with Na+
6) lactic acid-active transport, along with Na+
7) water-osmosis because of the concentration gradient resulting from active transport of Na+ and other solutes
8) there are others to choose from

Question 17

Describe the differences between the descending and ascending limbs of the loop of
Henle, in terms of reabsorption (3 marks).

Answer 17

• the descending limb is permeable to water so water moves out of the loop into the interstitial fluid and reaches a concentration equal to that in the surrounding interstitial fluid
• the ascending limb is impermeable to water but Na+, K+ and Cl- can be pumped out of the filtrate , lowering its concentration so that it becomes less concentrated than the plasma

Question 18

Describe how solute concentration varies throughout the interstitial fluid of the
kidney.

Answer 18

• in the cortex, the concentration of the interstitial fluid is comparable to that of the blood - about 300 mOsm/L
• the concentration of the interstitial fluid increases towards the medulla reaching a maximum concentration of about 1200 mOsm/L

Question 19

Describe the main substances that are reabsorbed by the distal tubule and the
mechanisms involved.

Answer 19

• Na+ and Cl- are reabsorbed by active transport
• Ca2+ is reabsorbed by active transport that is controlled by the hormone PTH
• water is reabsorbed by osmosis

Question 20

Describe the main substances that are reabsorbed by the collecting duct and the
mechanisms involved.

Answer 20

• Na+ is reabsorbed by active transport

- water is reabsorbed by osmosis

Question 21

Aldosterone is released by the _____________ in response to:

a) ____________________ b) ____________________ c) ____________________

Answer 21

adrenal cortex

a) angiotensin II
b) low plasma Na+
c) high plasma K+

Question 22

Explain where and how aldosterone acts.

Answer 22

• aldosterone acts to increase the action of transport proteins in the distal convoluted tubule that reabsorb Na+ and secrete K+
• aldostere has three actions:
  1) increased retention of Na+ in plasma
  2) increased retention of water in plasma (because of Na+ retention)
  3) increased elimination of K+

Question 23

List three substances that are secreted into the tubular filtrat

Answer 23

1) hydrogen ions (H+)
2) potassium ions (K+)
3) some organic ions, like antibiotics

Question 24

The other name of ADH is ______________

Answer 24

vasopressin

Question 25

Describe where ADH is produced and what triggers its production.

Answer 25

-ADH is produced in the hypothalamus (released from posterior pituitary) when osmoreceptors in the hypothalamus are stimulated by increased solute concentration of the blood (dehydration)

Question 26

Describe the action of ADH in the kidneys and the effects that this has on general
physiology (2 marks).

Answer 26

• ADH increases the number of aquporin proteins (water channels) in the distal convoluted tubule and collecting duct, allowing more water to be reabsorbed from the filtrate
• increased water reabsorption reduces urinary output, increases blood volume and tends to increase blood pressure

Question 27

The movement of urine through the ureters is the result of _________________,
which is stimulated by ______________________.

Answer 27

peristalsis

parasympathetic nervous activity

Question 28

Describe the control of urination in the normal adult (2 marks).

Answer 28

• stretch receptors in the bladder send signals to the lower spinal cord and then to the pons
• the pons communicates with higher centers and when it is “judged” to be a good time, impulses are conducted along parasympathetic pathways to detrusor muscle of bladder (to contract) and to internal and external urinary sphincters (to relax)