Renal physiology 2 Flashcards
What type of filtration occurs in the golmerulus and what does this reuqire
Relative non-selective free filtration -
Requires – filtration barrier, driving force, blood flow
What are the four factors to the driving force of glomerular filtration
Osmotic pressure apply a pull
Hydrostatic pressure apply a push
Promoting filtration
glomerular hydrostatic pressure ~50mmHg
Capsular colloid osmotic pressure ~0
Inhibiting filtration
Capsular hydrostatic pressure ~15mmHg
Blood colloid osmotic pressure ~ 25mmHg
Define + value
renal blood flow,
renal plasma flow
glomerular filtration rate
and filtration factor
Renal blood flow = % of CO as renal flow ~ 1/5 CO
Renal plasma flow = % of RBF as plasma 0.55*RBF ~625ml/min
Filtration fraction = amount of RPF filtered ~20%
Glomerular filtration rate = amount of plasma filtered FF * RPF
~125ml/min -> 180ml/day
- GFR tightly regulated > decrease with age
What are the requirements for a substance to be a good metric of the glomerular filtration rate
Common usage
Must be free filtered
Must not be absorbed or secreted
Creatinine (biproduct of muscles) often used
inulin (undigestable polysacharide) used but must be injected
How can GFR be approximated using a viable substance
creatinine normally used as an indicator of GFR
Conc plotted againt GFR
Meaning -
125 - functional
60 - 1 kidney functional (perfectly viable)
25 - kidney failing to remove waste
15 - kidney failure
What is the renal filtered load
total amount of a substance which is filtered
RFL = conc in plasma * GFR
- all renal filtered load is not nessissarily excreated
