3 Glomerular Filtration

Question 1

What are the 2 forces involved in Bulk flow?

Answer 1

hydrostatic

osmotic / oncotic

Question 2

What is oncotic pressure?

Answer 2

osmotic pressure of proteins, as lil ions can freely pass over the barrier so have little effect with osmosis

Question 3

What happens to hydrostatic pressure over the length of the glomerular capillaries?

Answer 3

is remains fairly constant

Question 4

What happens to the oncotic pressure over the length of the glomerular capillaries?

Answer 4

it increases but never exceeds the hydrostatic pressure

Question 5

what are the 3 layers in the glomerular barrier to diffusion?

Answer 5

endothelial cell of glomerular capillaries

glomerular basement membrane

epithelial cells of bowman’s capsule

Question 6

What are the features of the endothelial cells of glomerular capillaries?

Answer 6

60nm fenestrations

negatively charged glycocalyx

Question 7

Name one feature of the glomerular basement membrane

Answer 7

has negatively charged proteins (like collagen)

Question 8

Do anions or cations stay in the blood more easily?

Answer 8

cations, repelled by negatively charged barrier

toxic substances are usually labelled by the liver to make them anionic - easily pass out

Question 9

What are podocytes?

Answer 9

epithelial cells of the bowman’s capsule

Question 10

name 2 features of podocytes

Answer 10

small pedicles joining with each other to form an extra barrier

foot processes…

Question 11

What effect does bulk flow have on solutes

Answer 11

they are carried with the solvent in solvent drag

Question 12

Why can’t diffusion really work in the glomerulus?

Answer 12

barrier is too thick or tortuous

Question 13

What molecules are filtered out in the glomerulus?

Answer 13

most molecules <10kDa
larger molecules if positively charged and glomerulus is a bit damaged

not usually molecules >100kDa

Question 14

What is filtration fraction?

Answer 14

the proportion of the plasma flow that is filtered by the gomerulus

ie - glomerular flow rate over renal plasma flow

Question 15

Name 2 ways we can increase glomerular capillary pressure?

Answer 15

dilate afferent arteriole

contract the efferent arteriole

Question 16

What sorts of substances do we use to measure GFR?

Answer 16

substances that are freely filtered, but neither secreted nor reabsorbed over the length of the tubules

Question 17

How can we measure creatinine in urine?

Answer 17

[creatinine urine] x volume

Question 18

How can we measure creatinine excretion rate using amount in urine?

Answer 18

[creatinine urine] x volume/time (Vdot)

Question 19

How can we measure creatinine excretion rate using GFR?

Answer 19

GFR x [creatinine plasma]

Question 20

How can we measure GFR?

Answer 20

GFR = ([Cu] x flow) / [Cp]

Question 21

What do we use to measure GFR in a single blood sample?

Answer 21

eGFR

Question 22

What is eGFR?

Answer 22

(140-Age)xmxC / [Cp]

Question 23

Why is the formula for eGFR only appropriate for adults?

Answer 23

as we age we lose nephrons, so GFR falls

this causes Cp to rise

Question 24

What might proteinuria suggest?

Answer 24

if severe - nephrotic syndrome

Question 25

What would you call a predominant dysfunction of the glomerulus?

Answer 25

glomerulonephritis

Question 26

What does Congenital Nephrotic syndrome involve?

Answer 26

problem with either Nephrin or Podocin, causing more plasma proteins to leave the blood