The document discusses acid-base balance and how the kidneys regulate pH levels in the blood. It notes that the normal pH range for blood is 7.35-7.45. The kidneys play a key role in regulating acid-base balance by reabsorbing bicarbonate ions and secreting hydrogen ions in response to acidosis to restore pH levels. In alkalosis, the kidneys secrete bicarbonate ions and reabsorb hydrogen ions. The kidneys are ultimately responsible for eliminating metabolic acids and bases from the body to maintain normal pH.

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Normal Acid-Base Balance
• Normal pH 7.35-7.45
• Narrow normal range
• Compatible with life 6.8 - 8.0
___/______/___/______/___
6.8 7.35
7.45 8.0
Acid Alkaline

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PH Scale

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Acid & Base
• Acid:
• An acid is "when hydrogen ions accumulate in a solution"
• It becomes more acidic
• [H+] increases = more acidity
• CO2 is an example of an acid.
Base:
A base is chemical that will remove hydrogen ions
from the solution
Bicarbonate is an example of a base.

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Acid and Base Containing
Food:
• To maintain health, the diet should consist of
60% alkaline forming foods and 40% acid
forming foods. To restore health, the diet should
consist of 80% alkaline forming foods and 20%
acid forming foods.
• Generally, alkaline forming foods include: most
fruits, green vegetables, peas, beans, lentils,
spices, herbs,seasonings,seeds and nuts.
• Generally, acid forming foods include: meat, fish,
poultry, eggs, grains, and legumes.

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Citric Acid And Lactic Acid
Although both citric acid and lactic acid are
acids
BUT
Citric acid leads to Alkalosis while Lactic
acid to Acidosis due to metabolism

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Acidoses & Alkalosis
• An abnormality in one or more of the pH
control mechanisms can cause one of two
major disturbances in Acid-BaseAcid-Base balance
– AcidosisAcidosis
– AlkalosisAlkalosis

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Acidosis
• Acidosis is excessive blood acidity caused by an
overabundance of acid in the blood or a loss of
bicarbonate from the blood (metabolic acidosis), or by a
buildup of carbon dioxide in the blood that results from
poor lung function or slow breathing (respiratory
acidosis).
• Blood acidity increases when people ingest substances
that contain or produce acid or when the lungs do not
expel enough carbon dioxide.

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Metabolic Acidosis
• Bicarbonate deficit - blood concentrations of
bicarb drop below 22mEq/L
• Causes:
–Loss of bicarbonate through diarrhea or
renal dysfunction
–Accumulation of acids (lactic acid or
ketones) which may occur in starvation
or high fever.
–Failure of kidneys to excrete H+

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Metabolic Acidosis(Cont)
- metabolic balance before
onset of acidosis pH 7.4
metabolic acidosis pH 7.1
HCO3
-
decreases because of
excess presence of ketones,
chloride or organic ions
- body’s
compensation- hyperactive breathing to “ blow off ”
CO2
- kidneys conserve HCO3
-
and eliminate
H+
ions in acidic urine
-therapy required to restore metabolic
balance

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Alkalosis
• Alkalosis is excessive blood alkalinity
caused by an overabundance of
bicarbonate in the blood or a loss of acid
from the blood (metabolic alkalosis), or by
a low level of carbon dioxide in the blood
that results from rapid or deep breathing
(respiratory alkalosis).

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Metabolic alkalosis
• Metabolic alkalosis is due to the gain of base
or the loss of acid. The primary abnormality is an
increased HCO3.
• Cause
• Caused from an increase in bicarbonate in
the blood because of ingestion of excess
bicarbonate in the form of an antacid (Tums),
eating excess fruits (vegetarian diets and fat
diets), loss of acid from vomiting, or loss of
potassium from diuretics.

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Metabolic alkalosis(contd)
- metabolic balance before onset of
alkalosis
- pH = 7.4
metabolic alkalosis pH = 7.7
- HCO3
-
increases because of loss of
chloride ions or excess ingestion of
NaHCO3
- body’s compensation
- breathing suppressed to hold CO2
- kidneys conserve H+
ions and
eliminate HCO3
-
in alkaline urine
- therapy required to restore metabolic
balance

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Effects Of Ph Change On Cell :
• Acidosis and alkalosis are not diseases
but rather are the results of a wide variety
of disorders
• pH changes have dramatic effects on
normal cell function
– 1)1) Changes in excitability of nerve and
muscle cells
– 2)2) Influences enzyme activity
– 3)3) Influences KK++
levels

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RESPONSES TO
ACIDOSIS AND ALKALOSIS
• Mechanisms protect the body against life-
threatening changes in hydrogen ion
concentration are
– 1) Buffering Systems in Body Fluids1) Buffering Systems in Body Fluids
– 2) Respiratory Responses2) Respiratory Responses
– 3) Renal Responses3) Renal Responses
– 4) Intracellular Shifts of Ions4) Intracellular Shifts of Ions

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RESPONSES TO
ACIDOSIS AND ALKALOSIS
• Buffer system: temporary solution
• ~Respiratory mechanism provide short
time regulation
• ~Renal mechanism : permanent solution

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• RENAL REGULATION OF
METABOLIC ACIDOSIS
AND ALKALOSIS

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Renal Regulation (Contd):
• Only the kidneys can rid the body of acids
generated by cellular metabolism
(nonvolatile or fixed acids)
• The kidney in response:
– To AcidosisTo Acidosis
• Retains bicarbonate ions and
eliminates hydrogen ions
– To AlkalosisTo Alkalosis
• Eliminates bicarbonate ions and
retains hydrogen ions

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Renal Regulation (Contd):
• To maintain normal pH, the kidneys must
perform 2 physiologic functions.
• 1.Reabsorb all the filtered HCO3:
• A function principally of the proximal
tubule.
• 2. To excrete the daily H+ load:
• A function of the collecting duct.

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Renal Regulation (Contd):
• Chemical buffers can tie up excess acids or bases, but
they cannot eliminate them from the body
• The lungs can eliminate carbonic acid by eliminating
carbon dioxide
• Only the kidneys can rid the body of metabolic acids
(phosphoric, uric, and lactic acids and ketones) and
prevent metabolic acidosis
• The ultimate acid-base regulatory organs are the kidneys
• The most important renal mechanisms for regulating
acid-base balance are conserving (reabsorbing) or
generating new bicarbonate ions and excreting
bicarbonate ions
• Losing a bicarbonate ion is the same as gaining a
hydrogen ion; reabsorbing a bicarbonate ion is the same
as losing a hydrogen ion

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Renal Regulation (Contd):
Reabsorption of Bicarbonate:
• Plasma bicarbonate is freely filtered at the glomerulus.
• Carbonic acid formed in filtrate dissociates to release
carbon dioxide and water
• Carbon dioxide then diffuses into tubule cells, where it
acts to trigger further hydrogen ion secretion
• For each hydrogen ion secreted, a sodium ion and a
bicarbonate ion are reabsorbed by the PCT cells
• Secreted hydrogen ions form carbonic acid
• Thus, bicarbonate disappears from filtrate at the same
rate that it enters the peritubular capillary blood

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Reabsorption of Bicarbonate
Ions:

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Renal Regulation (Contd):
• Generating New Bicarbonate Ions:
• Two mechanisms carried out by tubule
cells generate new bicarbonate ions
• Both involve renal excretion of acid via
secretion and excretion of hydrogen ions
or ammonium ions (NH4+)

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Renal Regulation (Contd):
Excretion Of Buffered H Ions:
Alpha intercalated cells of the renal
tubules can synthesize new
bicarbonate ions while excreting
more hydrogen ions.

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Excretion Of Buffered H+:(Cont)
• In response to acidosis hydrogen ions must be
counteracted by generating new bicarbonate
• Kidneys generate bicarbonate ions and add them to the
blood
• An equal amount of hydrogen ions are added to the
urine
• Dietary:The excreted hydrogen ions must bind to buffers
(phosphate buffer system) in the urine and excreted
• Bicarbonate generated is then moved into the interstitial
space via a cotransport system
• Passively moved into the peritubular capillary blood

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Synthesis Of New Bicarbonate &
Excretion Of Buffered H+:

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Renal Regulation (Contd):
Excretion Of Ammonium Ion :
• Ammonium ions are weak acids.
• This method uses ammonium ions
produced by the metabolism of glutamine
in PCT cells
• Each glutamine metabolized produces two
ammonium ions and two bicarbonate ions
• Bicarbonate moves to the blood and
ammonium ions are excreted in urine

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NH4+ Excretion :

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ACIDIFICATION OF URINE BY EXCRETION OF AMMONIA
Capillar
y
Distal Tubule
Cells
Tubular
urine to be
excreted
NH2
H
+
NH3
NH2
H
+
NH3
WHAT
HAPPENS
NEXT?

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Capillar
y
Distal Tubule
Cells
Tubular
Urine
NH3
Na
+
Cl-
+
H2CO
3
HCO3
-
+
NaCl
NaHCO3
Click Mouse to Start
Animation
NaHCO3
NH3Cl-
H
+
NH4Cl
Click Mouse to See
Animation Again
Notice the
H+
- Na+
exchange to
maintain
electrical
neutrality
ACIDIFICATION OF URINE BY EXCRETION OF AMMONIA
Dissociation
of carbonic
acid

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Renal Regulation (Contd):
• Bicarbonate Ion Secretion
• When the body is in alkalosis, tubular cells
secrete bicarbonate ions and reclaim
hydrogen ions and acidify the blood
• This mechanism is the opposite of
bicarbonate ion reabsorption process

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Bicarbonate Ion Secretion

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Daily Reabsorption of HCO-3 By
Kidney:
• 85% HCO-3 reabsorption (H+ Secretion)
occurs in PCT (proximal convuluted
tubule)
•  10% HCO-3 reabsorption (H+ secretion)
occurs in thick ascending LOH
•  4.9% (approx 5%) reabsorption (H+
secretion) occurs in DCT & CT.
• For each HCO3 reabsorbed, there must
be one H+ ion secreted.

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THANK YOU