Now in the intercalated disc, one step further
you must know that this hydrogen that is being
pumped out into the lumen or the urine works
to the hydrogen-potassium pump. It all begins
with the sodium-potassium pump on the basolateral
membrane. Now be careful there all that I
wish for you to do technically is to work
with that hydrogen. One other piece of news
that I wish to give to you here is that
hydrogen that is being pumped out. Do you
see it now versus NH4. That is ammonium, and that
is an incredibly important buffer actually
most to be hydrogen is buffered through ammonia. Do you
remember where ammonia was produced and synthesized?
Way back in the proximal convoluted tubule.
I told you at that time that we would see
here in terms of its buffering effect with
hydrogen. So ammonia, NH3 when it takes up
hydrogen is now called ammonium or you have titrated
acid and that is going to be a phosphate.
So whenever you have heard in physiology as
titrated acid, this then means that this is
then going to pick up hydrogen in the hopes
of trying to buffer that hydrogen and tell
me about that bicarb is this reabsorbed, is
it newly synthesized? It is newly synthesized.
Where every single cell goes through glycolysis,
doesn't it? As human beings, we have aerobic
glycolysis hopefully majority of the time
and so therefore as you go through TCA cycle,
take a look at the very left there, you see
that carbon dioxide, where is it coming from?
TCA cycle. You give outside carbon dioxide.
All of this is going to help you contribute to
the forward movement and production of hydrogen
and bicarb. That hydrogen potassium pump located
in the collecting duct , primary site for
hydrogen to get rid of. Potassium technically
is reabsorbed, but now this is titratable
acid. Please know. Pay attention that phosphate
to you should mean titratable acidity. Now
that is more technical. It is more of a research
thing, but know the name, memorize it, please.
Is this majority of how hydrogen is buffered?
No, no, no. It is one of the ways. This is
the majority of how hydrogen is buffered.
Look and highlight in your head NH3. That
is ammonia. It will then pick up the hydrogen
and end up forming ammonium and we talked
about ammonia in greater detail earlier. We
talk about ammonia having a alkaline nature.
We talked about the struvite staghorn stone
with magnesium ammonia phosphate. Talked about
asterixis as well, with liver damage.
Both titratable acids in ammonia, acidifies
the urine. Bicarb is synthesized and reabsorbed
into the ECF. This is the primary site for
regeneration of a bicarb if need be.