PHSI 208 Lecture Notes - Lecture 2: Renal Function, Macula Densa, Renal Blood Flow
Document Summary
Glomerular filtration rate (gfr) is the volume of fluid that filters from the glomerular capillaries into the bowman"s capsules per unit of time. Our plasma volume is about 3l, meaning that the kidneys filter our entire plasma volume approximately 60 times per day. If it was not reabsorbed, we would run out of plasma in about. Two factors influence gfr: net filtration pressure: depends on renal blood flow and blood pressure, filtration coefficient: the surface area of the glomerular capillaries available for filtration and permeability of interface between capillaries and bowman"s capsule. This is controlled by podocytes in mesangial cells. Gfr is relatively constant over a wide range of blood pressures. It is usually 180l/day, due to auto-regulatory control. Gfr is primarily regulated by renal arterioles, both afferent and efferent. Auto-regulation maintains a nearly constant gfr when mean arterial blood pressure is between. Resistance changes in renal arterioles alter renal blood flow and gfr.
