Glomerular Filtration

Question 1

why are the kidneys so venerable to vascular disease?

Answer 1

they receive a high blood flow (20-25%) of cardiac output

Question 2

what is the normal glomerular filtration rate?

Answer 2

125mls/min

Question 3

what is the glomerular filtration dependent on?

Answer 3

balance between hydrostatic forces favouring filtration and oncotic pressure favouring reabsorption

Question 4

what determines the filterability of solutes across the glomerular filtration barrier?

Answer 4

> molecular size
shape
electrical charge

Question 5

what are the three layers of the filtration membrane?

Answer 5

> glomerular endothelial cells
basal lamina
slit membrane between podocytes

Question 6

why is the glomerular capillary pressure higher than most capillaries?

Answer 6

the afferent arteriole is short and wide, offering little resistance to flow

Question 7

describe to efferent arteriole in the glomerulu

Answer 7

long and narrow, offering a high post capillary resistance

Question 8

true or false:

high resistance means there will be and increase in pressure up stream and a decrease in pressure downstream

Answer 8

true

Question 9

at the glomerulus dos hydrostatic pressure exceed oncotic pressure?

Answer 9

yes as this favours filtration

Question 10

what is the primary factor affecting GFR?

Answer 10

the hydrostatic pressure in the glomerular capillary

Question 11

what is the extrinsic control of GFR?

Answer 11

> sympathetic vasoconstriction nerves
circulating catecholamines
angiotensin 2

Question 12

what does circulating catecholiamines constrict?

Answer 12

the afferent capillary

Question 13

what does angiotensin 2 constrict in the kidney?

Answer 13

> low: efferent

> high: afferent and efferent

Question 14

how does renal vasculature intrinsically adjust its resistance?

Answer 14

autoregulation

Question 15

what is the autonomic affect if the afferent arteriole in the kidney is the mean arterial pressure increases?

Answer 15

there is an increase in constriction to prevent rise in glomerular capillary pressure

Question 16

what is the auto regulatory range in man?

Answer 16

60-130mmHg

Question 17

in blood volume compromise (haemorrhage) describe the interaction between the intrinsic and extrinsic controls?

Answer 17

activation of the sympathetic vasoconstriction nerves and angiotensin 2 overrides autoregulation liberating more blood from the kidney to other important organs

Question 18

true or false:

the hydrostatic pressure is very high in peritubular capillaries

Answer 18

false (the pressure is overcoming the frictional resistance in efferent arterioles)

Question 19

in peritubular capillaries what is higher the oncotic pressure of the hydrostatic pressure?

Answer 19

oncotic pressure

Question 20

how much of the plasma is filtered into the bowmans capsule?

Answer 20

20%

Question 21

what is filtered at the glomerulus then reabsorbed within the tubule?

Answer 21

> 99% H2O
100% glucose
99.5% Na+
50% urea