Flashcards in Elements of Renal Function Deck (51):
regulate ECF concentration
regulate plasma electrolyte concentration
regulate acid base balance
regulate extracellular fluid volume, arterial blood presure
eliminate metabolic waste
hormones in kidney?
synthesized in kidney?
kidney is important?
integrated with many other body systems
renal failure: anemia, osteoporisis, disregulation of calcium and phosphate
kidneys a blood pressure
renal blood supply
20% cardiac output
glomerular capillaries - 60 mmHg
pressure in peritubular capillaries
lower (13 mmHg)
permits fluid reabsorption
pressure in capillary beds?
can be regulated by resistance changes in afferent and efferent arterioles
two types of nephrons?
juxtamedullary (much longer loops of henle)
short loop of henle
-surrounded by peritubular capillaries
long loop of henle
-long efferent arterioles divided into specialized peritubular capillaries (vasa recta)
runs alongside loos of henle in juxtamedullary nephron
first capillary network?
-high hydrostatic pressure
-large fluid volume filtered in bowmans capsule
second capillary network?
-low hydrostatic pressure
-law amounts of water and solute are reabsorbed
renal blood flow
very high flow
renal flow during exercise?
-blood is shunted to skeletal muscle
flow rates in regions of kidney?
slower as get more central (outer to inner medulla)
slow rate in medulla allows concentration of urine
innervation of kidney?
sympathetics on smooth muscle on arterioles and granular cells in afferent arterioles
on juxtaglomerular apparatus
-sympathetic stimulation of renin release
powerful constriction of afferent and efferent arterioles
-afferent > efferent
decreases renal blood flow
diverts renal fraction to vital organs
also stimulates renin release
stimulates Na+ reabsorption in proximal tubule, thick ascending loop of henle, distal convoluted duct, collecting duct
filtration of plasma from glomerular capillaries into bowmans capsule
transferral of substances from tubular lumen to peritubular capillaries
transferral of substances from peritubular capillaries to tubular lumen
voiding of substances in urine
urinary excretion = ?
amount filtered - reabsorbed + secreted
tubular reabsorption = ?
glomerular filtration - urinary excretion
if excretion rate > filtration rate, tubular secretion must have occurred
glomerular filtration rate
volume of plasma filtered into combined nephron of both kidneys per unit time
GFR x plasma concentration of substance
urinary excrection rate?
flow rate x concentration of substance in urine
reabsorption or secretion of substance?
difference between glomerular filtration and urinary excretion (assuming substance is not produced or metabolized by kidneys)
excretion < filtration
net reabsorption occured
excretion > filtration
net secretion occured
volume of plasma from which a substance is completely removed by kidney in given time period
describes how effectively the kidneys remove a substance from the bloodstream and excrete it in the urine
different substances have different clearance
GFR measure depends on clearance
clearance of substance = ?
concentration in urine x urine volume /
concentration of substance in plasma
Cx = Ux x V / Px ***
can be done using clearance
-if compound freely filtered, but NOT secreted, reabsorbed, produced, nor degraded by the kidneys
freely filtered, not reabsorbed, secreted, or metabolized
inulin clearance equal to GFR
problems - need to inject it
another estimate of GFR
-freely filtered, but not perfect
creatinine secretion in proximal tubule overestimates Ux; substances in blood cause overestimation of Px
two sources of error nearly cancel eachother out
P-creatinine and GFR?
not perfect, difference in lean muscle
compensatory increased proximal tubule secretion
uses of creatinine?
long term function
creatinine from muscle
BUN from liver (waste product)
urea reabsorbed by tubules can be regulated
creatinine reabsorbed remains the same
-BUN reabsorption is increased
-due to hypovolemia
creatinine doesn't change with hypovolemia
normal range or postrenal
-can be postrenal disease (obstruction)
-renal damage causes reduced reabsorption of BUN and a lower BUN/Cr ratio
another marker of GFR
-produced by all nucleated cells
-not dependent on muscle mass or gender
it goes up, GFR goes down
used to determine estimage GFR (eGFR)
para-amino hippuric acid (PAH)
freely filtered and avidly secreted
-completely cleared from plasma of peritubular capillaries
gives estimate of blood flow
renal plasma flow through the tubule
FF = GFR/RPF
RPF = renal plasma flow