Ultrafiltration

Where does ultrafiltration occur

In the renal capsule

What is ultrafiltration ‘powered by’

High blood pressure, or hydrostatic pressure, in the glomerulus forces plasma and small solutes through glomerulus walls and into the renal capsule

How is high hydrostatic pressure created in the glomerulus

The afferent arteriole (entering renal capsule) has a wider lumen than the efferent arteriole (leaving renal capsule)

What 3 layers does filtrate pass through

Endothelium of the capillary, basement membrane and epithelium cells of the capsule (podocytes)

What is an adaptation of the endothelium of the capillary for ultrafiltration

The endothelium has tiny pores, or fenestrations, which are too small for cells and plasma proteins to leave the blood

Which structure in the renal capsule actually acts as the filter

Basement membrane

What size molecules does the basement membrane prevent passing through

Molecules with a relative molecular mass of 68,000 or larger

What are the cells of the renal capsule wall called and why

Podocytes, because they have feet-like extensions

What are the gaps between podocytes called and what do they allow

Filtration slits, allow fluid to pass into the lumen of the renal capsule

What is the main difference between glomerular filtrate and blood plasma

Glomerular filtrate lacks large plasma proteins

What determines the rate of glomerular filtration

The difference in water potential between plasma in glomerular capillaries and filtrate in renal capsule