lecture 32

Question 1

what is the product of filtration?

Answer 1

creates a plasma-like filtrate of the blood

Question 2

what is the rate of filtration at glomerular?

Answer 2

125mL/min = 180L/day

Question 3

what supplies the blood for filtration?

Answer 3

afferent arterioles

Question 4

why does the DCT come back onto the efferent arteriole?

Answer 4

to control blood pressure by sensing how much NaCl has reached DCT

Question 5

what is the blood flow to the renal system?

Answer 5

1-1.2L/min = 20-25% of cardiac output

Question 6

Why does the renal system have high blood flow?

Answer 6

high flow for filtration rather than metabolism

Question 7

where does filtration take place?

Answer 7

in the glomerulus

Question 8

what is the filtration membrane composed of?

Answer 8

fenestrated epithelium
basement membrane
podocytes with foot processes and filtration slits

Question 9

what are the driving forces of glomerular filtration?

Answer 9

forces/ pressure gradients between glomerular capillary / capillary space
permeability of glomerular
surface area of glomerular

Question 10

4 forces determining net filtration?

Answer 10

GHP
BCOP
CsHP
CsCOP

Question 11

what is the value of net filtration pressure?

Answer 11

+10mmHG

Question 12

what is the main pressure of the glomerular?

Answer 12

Blood pressure (+50mmHg)

Question 13

what are the two opposing forces?

Answer 13

blood colloid osmotic pressure and capsular hydrostatic pressure

Question 14

what are the values of the two opposing forces?

Answer 14

• 25mmHg

- 15mmHg

Question 15

why is the capsular colloid osmotic pressure 0?

Answer 15

no protein in capsular space

Question 16

what is the equation for clearance?

Answer 16

U x V / P (mL/min)

Question 17

what are the defining factors of renal clearance?

Answer 17

concentration of Substance in urine
volume of urine produced per unit time
concentration of substance in plasma

Question 18

what does the renal clearance describe?

Answer 18

the rate at which substance S is cleared by the kidneys per unit time

Question 19

what is GFR?

Answer 19

glomerular filtration rate

amount of fluid filtered per unit time

Question 20

Why does GFR decline?

Answer 20

it declines slowly from age 30

Question 21

To be used as a measure of GFR a substance must?

Answer 21

mot be reabsorbed by tubule
not be secreted into the tubule
not be metabolised

Question 22

two main substances that can measure GFR?

Answer 22

inulin

creatinine

Question 23

what is inulin?

Answer 23

polysaccharide not metabolised by body

must be injected

Question 24

what is creatinine?

Answer 24

waste product produced by muscles

already in body

Question 25

what does it mean if plasma creatinine is low?

Answer 25

both kidneys are working

Question 26

what is the creatinine value for only one working kidney?

Answer 26

60mL/min

Question 27

how much of plasma is filtered?

Answer 27

renal blood flow is 25%/min = 1.25L
50% of blood is plasma
only 125mL/min is filtered
=> 20% (125/625)

Question 28

what is the filtration fraction?

Answer 28

(GFR/RPF) = 20%

Question 29

what is filtered load?

Answer 29

amount of a particular substance filtered per minute?

Question 30

filtered load =?

Answer 30

GFR x solute plasma conc.