RBF & GFR Flashcards
what % of cardiac output (CO) do the kidneys receive at rest
20%
(1 L/min, if CO is 5 L/min)
what % of the plasma volume that enters the kidneys is filtered
20%
what organ has the highest mass specific flow rate to any organ in the body
kidneys
blood volume leaving kidneys via renal vein = _____
blood volume entering kidneys via renal arteries
equation for mass specific flow rate
= flow rate / mass of the organ
renal mass specific flow =
400 ml / 100 g/min
GI and liver mass specific flow =
100 ml / 100 g/min
heart and brain mass specific flow =
50-70 ml / 100 g/min
skeletal muscle mass specific flow =
5 ml / 100 g/min
what is mass specific flow rate
the flow per gram of tissue
what does the high pressure of the glomerular capillaries cause
net filtration of fluid into the nephron
what does the low pressure of the peritubular capillaries cause
net reabsorption of fluid & solutes back into the blood stream
2 unique components of blood flow in the nephron
2 resistance vessels (arterioles) in series- on either side of glomerular capillaries
2 sets of capillary beds (divides labor of filtration & reabsorption between them)
how much RBF does the cortex receive, what does this do for the nephron
90-95%
maximizes flow dependent processes
what does the RBF look like in the medulla, and why
restricted RBF going into the medulla
bc of the high resistance of the descending peritubular capillaries
another name for peritubular capillaries
vasa recta capillaries
why is it important to have low RBF through the medulla
in order to produce & maintain the osmotic gradient between ISF and medullary portion of nephron
why might there be potential for hypoxic injury in the outer medulla
bc low RBF here could limit oxygen availability
3 reasons we need high cortical RBF
-to keep high glomerular filtration rates
-to reabsorb most of the filtered water/solutes (via active transepithelial transport)
-to deliver nutrients & O2 to renal cells to support renal metabolism
what % of total body BMR (basal metabolic rate) do the kidneys use
7.5% (mostly the cortex)
what are the 2 organs (in order) with the highest mass specific O2 consumption rate (O2 consumption / per gram of tissue)
1) heart
2) kidneys
equation for RBF
RBF = delta P / R
blood flow rate entering kidneys = _____
blood flow rate exiting kidneys
(in a healthy person) initial filtrate / tubular fluid in Bowman’s space = _____, except _____
very similar composition (of inorganic ions, organic solutes) to plasma
except very little proteins and NO blood cells