Originally Posted by apx85
Can anyone explain what this is and how/if it relates to GFR?
Basically, the peritubular capillaries are AFTER efferent arterioles so they help in reabsorption. If the pressure is low, more fluid is reabsorbed. If the pressure is high, more fluid is secreted.
Heres an image -
Heres a detailed explanation from a source -
"Renal circulation is unique in that it has two capillary beds; the glomerular and peri-tubular capillaries which are arranged in series and separated by efferent arterioles that help regulate the hydrostatic pressures in both sets of capillaries. High hydrostatic pressure in glomerular capillaries (about 60 mm of Hg) causes rapid fluid filtration, lower hydrostatic pressure in peritubular capillaries (about 13 mm of Hg) permits rapid fluid reabsorption. By adjusting the resistances of afferent and efferent arterioles, kidneys regulate the hydrostatic pressures in both glomerular and peritubular capillaries, thereby changing rate of glomerular filtration or tubular reabsorption in response to body homoeostatic demands."