lecture 32 Flashcards
what is the product of filtration?
creates a plasma-like filtrate of the blood
what is the rate of filtration at glomerular?
125mL/min = 180L/day
what supplies the blood for filtration?
afferent arterioles
why does the DCT come back onto the efferent arteriole?
to control blood pressure by sensing how much NaCl has reached DCT
what is the blood flow to the renal system?
1-1.2L/min = 20-25% of cardiac output
Why does the renal system have high blood flow?
high flow for filtration rather than metabolism
where does filtration take place?
in the glomerulus
what is the filtration membrane composed of?
fenestrated epithelium
basement membrane
podocytes with foot processes and filtration slits
what are the driving forces of glomerular filtration?
forces/ pressure gradients between glomerular capillary / capillary space
permeability of glomerular
surface area of glomerular
4 forces determining net filtration?
GHP
BCOP
CsHP
CsCOP
what is the value of net filtration pressure?
+10mmHG
what is the main pressure of the glomerular?
Blood pressure (+50mmHg)
what are the two opposing forces?
blood colloid osmotic pressure and capsular hydrostatic pressure
what are the values of the two opposing forces?
- 25mmHg
- 15mmHg
why is the capsular colloid osmotic pressure 0?
no protein in capsular space
what is the equation for clearance?
U x V / P (mL/min)
what are the defining factors of renal clearance?
concentration of Substance in urine
volume of urine produced per unit time
concentration of substance in plasma
what does the renal clearance describe?
the rate at which substance S is cleared by the kidneys per unit time
what is GFR?
glomerular filtration rate
amount of fluid filtered per unit time
Why does GFR decline?
it declines slowly from age 30
To be used as a measure of GFR a substance must?
mot be reabsorbed by tubule
not be secreted into the tubule
not be metabolised
two main substances that can measure GFR?
inulin
creatinine
what is inulin?
polysaccharide not metabolised by body
must be injected
what is creatinine?
waste product produced by muscles
already in body
what does it mean if plasma creatinine is low?
both kidneys are working
what is the creatinine value for only one working kidney?
60mL/min
how much of plasma is filtered?
renal blood flow is 25%/min = 1.25L
50% of blood is plasma
only 125mL/min is filtered
=> 20% (125/625)
what is the filtration fraction?
(GFR/RPF) = 20%
what is filtered load?
amount of a particular substance filtered per minute?
filtered load =?
GFR x solute plasma conc.
