26. Renal Control of Acid/Base Balance Flashcards
What range does blood pH need to remain in?
7.35-7.45
What processes increase the amount of acid in blood?
- Metabolism produces CO2
- Breakdown of food produces non-volatile acids
- Metabolic intermediates (eg. lactic acid)
What are the 4 buffering systems in the body?
Bicarbonate
Phosphate
Haemoglobin
Plasma and cell proteins
What organs maintain blood pH?
Lungs (blow off CO2)
Kidneys (Control HCO3-)
What does blood pH depend on?
Ratio of HCO3- to H2CO3-
In practice, pCO2 is used for H2CO3
What concentration of HCO3- do the kidneys maintain?
24mmol/L
What pCO2 is maintained at by the lungs?
40mmHg
What concentration is H2CO3 maintained at?
1.2mmol/L
What is the Henderson-Hasselbach equation?
pKa+ log (base/acid)
What ratio of HCO3-/H2CO3 is needed to maintain a pH of 7.4?
20:1
What compensation occurs when acid is added to the blood?
- Bicarbonate is used up as a buffer
H2CO3 is broken to CO@ and H2O - CO2 can be blown off by the lungs
- Kidneys add new HCO3- to the blood and secrete H+
How do the kidneys control pH balance?
Reabsorb filtered bicarb
Make new bicarbonate (equal to amount used up by buffering)
Tubular secretion of H+
How is HCO3- reabsorbed?
H2CO3 converted to water and CO2 in the filtrate
These recombine in the tubular cell to produce H+ and HCO3-
HCO3- crosses basolateral membrane and H+ is secreted
How is bicarbonate made in the tubular cell?
CO2 from blood combined with OH- from water
Remaining H+ is buffered by HPO4^2-
What transporters are used to secrete H+?
ATP-driven H+ pump in CD
Na/H exchanger in PCT, DT, CD
H/K exchanger
