Glomerular Filtration

Question 1

List the route fluid travels in glomerular filtration.

Answer 1

1. Fenestrated endothelium
2. BM
3. Parietal epithelium (podocytes) b/t foot processes

Question 2

Rank from most to least likely to be in the glomerular filtrate: anionic, neutral and cationic.

Answer 2

Cationic > neutral > anionic

b/c BM is negatively charged

Question 3

Define Permselectivity

Answer 3

:size and charge determine if it can pass (the glomerulus)

Question 4

List the two factors affecting glom barrier passage.

Answer 4

Size (radius-but also shape and deformability)

Charge (only affects macromolecules)

Question 5

What molecules can freely pass through the glomerular barrier?

Answer 5

Molecules <7000 d : water, small ions, glucose, AA, small hormones

Question 6

Describe two reasons why there could be protein in the urine.

Answer 6

Glomerular proteinuria –> damage to glomerulus that allows it through
Tubular proteinuria –> proximal tubules are damaged not reabsorbing the proteins

Question 7

What is the equation for Glomerular filtration rate (GFR)?

Answer 7

GFR= Kf x NFP
Kf= ultrafiltration coefficient (product of permeability and SA)
NFP= net filtration pressure (what we can influence most, RAAS system)

Question 8

What is the equation for Net Filtration Pressure?

Answer 8

NFP= (Pgc - pi gc) - (Pbs - pi bs)
Pgc=hydraulic pressure in glomerular capillary
pi gc= plasma oncotic P in glomerular capillary
Pbs= Hydraulic pressure in Bowmans space
pi bs= Oncotic pressure in Bowmans space.

Question 9

Does the capillary hydraulic P change greatly b/t the beginning and end of the glomerular capillaries?

Answer 9

NO

Question 10

Does net filtration pressure change much b/t the beginning and end of the glomerular capillaries?

Answer 10

YES

oncotic pressure increases going along the tubule , removing water, protein remains, intercapillary pressure has gone up

Question 11

How does relaxation of glomerular mesangial cells, expanding the glomerular filter affect GFR?

Answer 11

Inc GFR, inc. size of filter will allow more filtration.

Question 12

How does afferent arteriolar dilation affect GFR?

Answer 12

Inc. GFR- inc. the fluid coming in, inc. the pressure

Question 13

How does efferent arteriolar dilation affect GFR?

Answer 13

Dec. GFR because lets pressure off the glomerular capillary system

Question 14

How does obstruction to the tubule or extrarenal urinary system affect GFR?

Answer 14

Decrease GFR b/c inc. pressure in bowmans space –> dec. GFR

Question 15

How does increased systemic oncotic pressure affect GFR?

Answer 15

Dec. GFR will negate some of the pressure in the glomerulus.

Question 16

How does decreased renal plasma flow affect GFR?

Answer 16

Dec. GFR, need higher filtration pressure to make up the GFR.

Question 17

How would you predict inc. protein binding would affect renal excretion of a drug excreted largely by glomerular filtration?

Answer 17

Decreased excretion.

Question 18

Benazepril selectively dilates the post-glomerular arteriole. In a patient with glomerular proteinuria, how would you predict it would affect proteinuria?

Answer 18

Decreased proteinuria, reduces pressure in the capillaries, less solute drag and protein goes down.

Question 19

How might an inc. in intraglomerular pressure influence the quantity of protein found in the final urine?

Answer 19

Inc. proteinuria

Question 20

What effect would a relative reduction in postglomerular arteriolar resistance have on filtration fraction?

Answer 20

Decreased filtration fraction.

Question 21

What effect would an inc. in filtration fraction have on peritubular capillary reabsorption?

Answer 21

Inc. reabsorption

Question 22

What are 4 things that qualify as “Nephronic Syndrome”?

Answer 22

1. Proteinuria
2. Hypoalbuminemia
3. Edema
4. Hyperlipidemia