3 - renal filtration, reabsorption and secretion

Question 1

3 basic renal processes?

Answer 1

filtration
reabsorption
secretion

Question 2

where does filtration take place?

Answer 2

glomerulus

Question 3

~% of plasma is in the filtrate?

Answer 3

20%

Question 4

normal GFR?

Answer 4

180 litres/day

125ml/min

Question 5

benefit of normal GFR being very high?

Answer 5

ample opportunities to -
regulate ECF volume and composition
eliminate harmful substances

Question 6

reabsorption in the PCT?

Answer 6

NaCl
H2O
amino acids
sugars

Question 7

reabsorption in the DCT?

Answer 7

NaCl

H2O

Question 8

purpose of secretion?

Answer 8

to specifically remove harmful substances

Question 9

why can damage to kidneys be lethal?

Answer 9

large blood supply and cardiac output

Question 10

consequence of having large cardiac output on the kidneys?

Answer 10

increased vulnerability of vascular disease

Question 11

how much cardiac output do the kidneys receive?

Answer 11

20-25%

Question 12

renal plasma flow?

Answer 12

660mls/min

Question 13

function of hydrostatic forces?

Answer 13

favours filtration by pushing blood into bowman’s capsule

Question 14

function of oncotic pressure forces?

Answer 14

favours reabsorption

Question 15

3 factors affecting the permselectivity of the glomerular barrier and substances being absorbed?

Answer 15

molcular size
electrical charge
shape of molecule

Question 16

what is the filtration fraction?

Answer 16

GFR / renal plasma flow x100

Question 17

why is Pgc higher than other capillaries?

Answer 17

due to the low resistance of the afferent arterioles

Question 18

what maximises pressure conditions within bowman’s capsules?

Answer 18

afferent arterioles being short, wide and therefore low resistance and pressure
AND
efferent arterioles being long, narrow and therefore high resistance and pressure

Question 19

Pgc - what is it always higher than and what is the result of this?

Answer 19

always higher than oncotic pressure -

therefore, filtration is always favoured

Question 20

golden rule of circulation?

Answer 20

high resistance causes increased hydrostatic pressure upstream while decreasing pressure downstream

Question 21

what occurs at glomerular capillaries?

Answer 21

ONLY filtration

Question 22

1y factor affecting GFR?

Answer 22

Pgc - which is dependent on afferent and efferent arteriolar diameter

Question 23

3 extrinsic factors affecting GFR?

Answer 23

sympathetic nerves
circulating catecholamines
angiotensin II

Question 24

effect of sympathetic n on GFR?

Answer 24

afferent and efferent vasoconstriction

Question 25

effect of circulating catecholamines on GFR?

Answer 25

afferent vasoconstriction

Question 26

effect of angiotensin II on GFR?

Answer 26

vasoconstriction of efferent at low concentrations, | vasoconstriction of efferent AND afferent at high concentrations

Question 27

result of increase in resistance of afferent arteriole?

Answer 27

decreased pressure of capillary blood | -> decreased GFR

Question 28

result of increase in resistance of efferent arteriole?

Answer 28

increased pressure of capillary blood | -> increased GFR

Question 29

result of decrease in resistance of afferent arteriole?

Answer 29

increased pressure of capillary blood | -> increased GFR

Question 30

normal range of BP?

Answer 30

60-130 mmHg

Question 31

what occurs when BP <60mmHg?

Answer 31

glomerular filtration decreases

Question 32

what occurs when BP=50mmHg?

Answer 32

glomerular filtration stops altogether

Question 33

result of increasing mean arterial pressure?

Answer 33

increased afferent arteriole constriction and therefore decreased pressure of capillary blood

Question 34

is auto regulation dependent on anything?

Answer 34

it is independent of nerves and hormones and it occurs in denervated and isolated kidneys

Question 35

what plays an important role in auto regulation?

Answer 35

blood volume

Question 36

reabsorption of peritubular capillaries - describe the efferent arterioles relationship to hydrostatic pressure?

Answer 36

efferent arterioles are long and narrow, therefore increasing the resistance and pressure this decreases the pressure of the blood and so the hydrostatic pressure also decreases to ~15mmHg