acid base balance and renal failure Flashcards
pH of plasma
cells like us to have that pH around 7.4
what happens we have changes in pH in plasma
- when we have extremes of acidity or alkalinity then the body is always trying to bring it back through using the renal system or the respiratory system
acidosis/ acidemia
- If our pH of the plasma or interstitial fluid surrounding the cell’s goes below 7.35 then we call it acidosis or if talking about the plasma is acidemia
alkalosis or Alkaliemia
if it goes above 7.45 we would suggest it was alkalosis or Alkaliemia
how do we regulate H+ - respiration
we are producing protons all the time in the body.
- One of the ways we’re producing them is through cellular respiration.
- when we have cell metabolism, we metabolize within the cell during cellular respiration and we produce carbon dioxide
- carbon dioxide combines with water to produce carbonic acid, which is an unstable volatile acid.
- This can dissociate to protons and bicarbonate ions.
- if we gain more CO2, plasma more acidic
- if we lose more CO2, plasma more alkaline
chemical buffering to maintain equilibrium of pH
2 substances which as part of a reversible reaction can either liberate or bind free H+ depending on the [H+]
- lungs eliminate carbon dioxide
- kidneys excrete H+ and conserve HCO3
Carbonic acid and bicarbonate buffer
major buffer in ECF
- CO2 and H20 diffuse into the cytoplasm
- carbonic anhydrase and the combination of water and co2 leads to carbonic acid, which is unstable and dissociates into bicarbonate and protons
- excess H+ drives this reaction to the left, so more carbon dioxide and water produced
the henderson - Hasselbalch equation
describes the relationship between pH carbon dioxide and bicarbonate
when can metabolic acidosis occur
metabolic acidosis can occur when the concentration of bicarbonate ions Falls or when the concentration of protons increases
- so we can have metabolic acidosis if we’ve got somebody who has got undiagnosed diabetes mellitus.
- Or if you’ve got somebody who’s got renal failure and they can’t excrete the protons So the proton levels also increase and they can’t reabsorb bicarbonate.
respiratory acidosis
we can get respiratory acidosis when you can’t get rid of the carbon dioxide. So if you’ve got a respiratory issue, so for example, you’ve got COPD or chronic bronchial asthma you can’t get rid of that excess carbon dioxide. So it starts to build up in the plasma and therefore the
individual have respiratory acidosis.
metabolic alkalosis
Metabolic alkalosis occurs when we have an increase in the amount of bicarbonate. (So if you ingest large amounts of bicarbonate) or if you’re losing a lot of acid because you vomiting and losing a lot of hydrochloric acid that way that can also cause problems with metabolic alkalosis.
respiratory alkalosis
respiratory alkalosis can occur if you’re getting rid of too much carbon dioxide. So if you’re hyperventilating your breathing off too much carbon dioxide, then the pH of your plasma will increase and you’ll have alkalosis
PCT cells
- secrete H+ ions
- reabsorb HCO3-
- excrete ammonium ions (helps generate bicarbonate ions)
type 4 intercalated cells in the collecting duct
- secrete H+ ions
- reabsorb bicarbonate ions
- excrete dihydrogen phosphate ions (helps generate bicarbonate
during alkalosis what do type B intercalated cells secrete
bicarbonate
what are the 3 ways kidneys excrete H+
- carbonic anhydrase (bicarbonate reabsorption)
- phosphate buffering
- ammonia/ammonium buffering. proteins acid (COO-)/base (NH4+) accept/donate H+
what is going on all the time to provide a source of bicarbonate or protons if required
the Carbonic anhydrase equation is happening inside the cells all the time and because of that we can either produce water and carbon dioxide or we can produce bicarbonate and protons - reversible reaction.
- The bicarbonate ions can be reabsorbed along with sodium and the protons can be then secreted back out into the Lumen where they can either be excreted or they can combine with bicarbonate ions that are already in the filtrate to form carbonic acid to then form water and carbon dioxide
- water can then be excreted in the urine
- carbon Dioxide can actually be reabsorbed through some of the aquaporins.
phosphate buffering
this occurs in many of the cells in the nephron
- occurs in PCT/DCT/CD
because we’ve got this going on in all the cells we can always combine
and form protons and bicarbonate ions.
The only difference here using the phosphate buffering system is in the filtrate We can get disodium hydrogen phosphate which can dissociate quite easily to free up protons.
- protons are readily available because this has been activated they can recombine to produce sodium dihydrogen phosphate and that’s quite stable.
excretion via the ammonium ion
we’ve got metabolism of some of the amino acids
when they metabolize they can produce bicarbonate ions as a by-product which can then be reabsorbed or they can produce ammonia
-Ammonia can cross the membrane again utilizing some of the pores
- We can get movement of your ammonia into the filtrate.
- Once it’s in the filtrate. It can mop up some of those free protons to produce the ammonium ion the nh4 plus
- the ammonium ion is impermeable to the apical membrane. So once the ammonium ions been produced it won’t dissociate and it’s another way That protons can be excreted in the urine.
kidney disease UK - the facts
- 1 in 10 will suffer chronic kidney disease, affecting all ages including children
- over 3 million people in the UK are being treated ofr kidney disease
- 1 in 5 people admitted to A&E have acute kidney injury
- 40-45000 die from chronic kidney disease each year
kidney disease - diabetes
- single largest cause of renal failure
- 2.6 million diabetics and climbing
- damage to large and small renal blood vessels due to hyperglycaemia
- results in lack of blood supply and sebsequent cell death
