Glomerular Filtration

Question 1

filtration volume per day of kidneys

Answer 1

180L/day

Question 2

the 3 basic renal processes

Answer 2

1. filtration
2. reabsorption
3. secretion (i.e. substances being excreted)

Question 3

what is excreted in proximal tubule

Answer 3

organic ions and drug metabolites

Question 4

what is excreted at distal tubule

Answer 4

K+ and H+

Question 5

what is reabsorbed in proximal tubule

Answer 5

NaCl, water, amino acids and glucose

Question 6

what is reabsorbed in distal tubule

Answer 6

NaCl and water

Question 7

if kidneys recieve 1200ml/min of blood how long does it take for the total BV to pass renal circulation

Answer 7

4 and a bit minutes

Question 8

how much red blood cells pass into bowman’s capsule

Answer 8

none

Question 9

how much plasma protein passes into the bowman’s capsule

Answer 9

very little but still some

Question 10

what is oncotic pressure

Answer 10

osmotic pressure created by proteins

Question 11

what is hydrostatic pressure

Answer 11

pressure exerted by a fluid

Question 12

what does Pgc stand for

Answer 12

glomerular capillary pressure

Question 13

what is the normal glomerular capillary pressure

Answer 13

55mmHg

Question 14

if you have resistance, hydrostatic pressure upstream is…

Answer 14

increased

Question 15

if you have resistance downstream, hydrostatic pressure is…

Answer 15

decreased

Question 16

what feature of glomerular capillaries (afferent and efferent) gives a high pressure

Answer 16

they are narrow

Question 17

which is higher, Pgc or oncotic and hydrostatic pressure of bowmen’s capsule

Answer 17

Pgc, because stuff needs to be pushed out of capillary and into bowman’s capsule

Question 18

net filtration pressure at renal corpuscle

Answer 18

10mmHg

Question 19

what are the pressures pushing back on glomerular capillary from bowmen’s capsule

Answer 19

osmotic pressure of proteins and hydrostatic pressure

Question 20

extrinsic controls of GFR

Answer 20

1. sympathetic nerves
2. circulating catecholamines (e.g. dopamine, E and NE)
3. angiotensin II

Question 21

what is normal GFR

Answer 21

125ml/min

Question 22

extrinsic controls of GFR have their effect

Answer 22

by constricting the afferent and/or efferent arterioles

Question 23

if the afferent arteriole is constricted what will be the effect on GFR

Answer 23

increased resistance of afferent –> decreased Pgc –> decreased GFR

Question 24

if the afferent arteriole is dilated what will be the effect on GFR

Answer 24

reduced resistance of afferent –> increased Pgc –> increased GFR

Question 25

if the efferent arteriole is constricted what will be the effect on GFR

Answer 25

increaesed resistance in efferent –> increased Pgc –> increased GFR

Question 26

intrinsic control of GFR

Answer 26

autoregulation by renal vasculature effective over a range of 60-130mmHg

Question 27

consequence on filtration when mean BP =< 50mmHg

Answer 27

filtration ceases

Question 28

if there is haemorrhage elsewhere in body what will be the kidney circulation response

Answer 28

extrinsic control can override autoregulation to direct blood to more immediately vital organ i.e. brain, heart, lungs

Question 29

what % of plasma passes into bowman’s capsule

Answer 29

20%

Question 30

how much of the plasma filtrate is reabsorbed

Answer 30

> 19%

Question 31

contents of plasma

Answer 31

95% water, proteins (albumin), glucose, clotting factors and electrolytes

Question 32

capillaries that filtrate is reabsorbed into from nephron

Answer 32

peritubular capillaries

Question 33

what do peritubular capillaries drain into

Answer 33

interlobular vein

Question 34

pathway of blood from renal artery to renal vein

Answer 34

renal artery –> segmental branch –> interlobular artery –> arcuate artery –> afferent arteriole –> glomerulus –> efferent arteriole –> peritubular capillary –> interlobular vein –> renal vein

Question 35

what % of fluid that is filtered through the glomerulus is excreted

Answer 35

1%

Question 36

pressure in peritubular capillary

Answer 36

lower ~15mmHg so that the nephron tubule pressure is greater and filtrate can be reabsorbed

Question 37

oncotic pressure of reabsorption

Answer 37

20% of blood plasma has been removed so the blood then in the peritubular capillaries has a higher concentration of proteins. Therefore there is also an osmotic oncotic pressure to reabsorb from the nephron tubules.