Lecture 5 - glomerular filtration 2

Question 1

What are the determinants of glomerular filtration?

Answer 1

Question 2

What is hydraulic conductivity?

Answer 2

defined as the flux of water (and small solutes) per unit time for a defined pressure gradient and surface area.

Question 3

What is the hydraulic conductivity of the glomerular capillary wall?

Answer 3

is 40 - 50 fold higher than other capillaries.

Question 4

What is the surface area of the glomerular capillary wall determined by?

Answer 4

▸ Determined by the available area for filtration

▸ Can be altered in many disease states

Question 5

What is the surface area?

Answer 5

▸ Human glomeruli measure, on average, 200 µm in diameter

▸ Estimated surface area of single glomeruli: 0.15 mm2

▸ Estimated glomerular number: ~ 2 X 106

▸ Total glomerular capillary surface area : ~ 0.3 m2

▸ Mesangial cells (contractile) may be able to modulate available surface area in response to vasoactive substances (e.g. Angiotensin II)

▸ Podocytes (actin cytoskeleton) may be involved in regulation of Kf by adjustment of filtration slit width

Question 6

What is the ultrafiltration coefficient (Kf) ?

Answer 6

the product of the hydraulic conductivity and the glomerular capillary surface area.

Question 7

What does glomerular filtration depend on?

Answer 7

1. Ultrafiltration coefficient (Kf)
2. Net Starling forces

Question 8

There is ……. across the entire length og the glomerular capillaries

Answer 8

net filtration