Final Exam

Question 1

what is the rate of renal blood flow?

Answer 1

1200 ml/minute

Question 2

what part of kidney has a high flow rate?

Answer 2

cortex

Question 3

blood enters glomerulus via _______ and leaves via ______

Answer 3

afferent arteriole; efferent arteriole

Question 4

endothelial cells have fenestrations. what do fenestrations allow?

Answer 4

allow filtration to occur at a faster rate

Question 5

what is GFR?

Answer 5

• rate at which plasma moves through glomerular capillaries
• females: 85-125 ml/min for 2 kidneys
• males: 97-140 ml/min for 2 kidneys

Question 6

at what age do children reach adult proportions in regards to GFR?

Answer 6

around 2 years of age

Question 7

what is the driving force of GFR?

Answer 7

• glomerular capillary hydrostatic pressure

Question 8

why does GFR lower with age?

Answer 8

as you age, you lose gomeruli

Question 9

pressure _____ as it goes from renal artery to arterioles

Answer 9

decreases

Question 10

determinants of GFR

Answer 10

GFR = Kf (Pgc - (Pt + COPgc))

Question 11

what is Kf?

Answer 11

• Kf = ultrafiltration coefficient. includes capillary surface area and fluid permeability
• tells us how open the filter is
• lower Kf = lower GFR

Question 12

what is Pgc?

Answer 12

Pgc = glomerular capillary pressure

Question 13

what is Pt?

Answer 13

• tubular pressure
• works against Pgc

Question 14

what is COP?

Answer 14

• colloid osmotic pressure
• pressure that is set up by the fact that there is albumin in the blood/plasma but there is no albumin on urine side
• albumin unable to get through filtration barrier
• water molecules on other side diffuse back in order to dilute albumin concentration
• the pressure of flow going backwards is called colloid osmotic pressure

Question 15

what is UFP?

Answer 15

• net filtration pressure (ultra)
  UFP = (Pgc - (Pt + COPgc))

Question 16

characteristics of a substance used to measure GFR

Answer 16

• must be freely filtered
• must not be reabsorbed or secreted
• must not be synthesized or catabolized by the kidney
• must not alter GFR

Question 17

substances used to measure GFR

Answer 17

• inulin (gold standard)
• creatinine (clinical standard)
• cystatin C

Question 18

why is creatinine the clinical standard?

Answer 18

• creatinine is excreted mainly by filtration
• produced by skeletal muscle at a constant rate from creatinine-phosphate

Question 19

what is the equation to calculate how much of a substance is secreted?

Answer 19

amount excreted = amount filtered - amount reabsorbed + amount secreted

Question 20

what RPF?

Answer 20

renal plasma flow rate

Question 21

P in x GFR = U in x V

Answer 21

P in = plasma inulin
U in = amount of inulin in urine
V = volume of urine over 24 hours

Question 22

measuring GFR - creatinine

Answer 22

GFR = ([Cr] urine x urinne flow rate (V/24hours)) / [Cr] plasma

Question 23

measuring GFR - creatinine - requirements

Answer 23

• 12-24 hour urine collection (timed)
• mid-point blood sample
• [Cr] in urine and plasma

Question 24

_____ clearance slightly _____ GFR

Answer 24

creatinine; overestimates

Question 25

plasma [creatinine] reflects _____ in _____-_____ conditions

Answer 25

GFR; steady-state

Question 26

creatinine is produced by _____ muscle at a _____ rate

Answer 26

skeletal; constant

Question 27

plasma _____ is _____ under _____ circumstances

Answer 27

[Cr]; constant; normal

Question 28

range of normal plasma [Cr] is _____

Answer 28

50-110 µmol/L

Question 29

if GFR _____, then excretion < production, so plasma [Cr] _____

Answer 29

decreases; increases