The kidneys maintain pH balance by reabsorbing bicarbonate and secreting hydrogen ions.
The Kidneys' Role in pH Balance
The kidneys play a crucial role in maintaining the body's acid-base balance (pH). They achieve this through two primary mechanisms, as highlighted in the reference:
- Reabsorbing Bicarbonate (HCO3-): The kidneys reclaim bicarbonate from the urine and return it to the bloodstream. Bicarbonate acts as a buffer, helping to neutralize acids in the blood.
- Secreting Hydrogen Ions (H+): The kidneys secrete hydrogen ions into the urine. This process removes acid from the body.
Key Principle: The kidneys fine-tune pH levels by adjusting the amounts of bicarbonate reabsorbed and hydrogen ions secreted.
How the Kidneys Adjust pH
The kidneys continuously monitor the blood's pH. If the blood is too acidic, the kidneys will:
- Reabsorb More Bicarbonate: This increases the concentration of bicarbonate in the blood, which helps to neutralize the excess acid.
- Secrete More Hydrogen Ions: This removes more acid from the body via the urine.
Conversely, if the blood is too alkaline (basic), the kidneys will:
- Reabsorb Less Bicarbonate: This decreases the concentration of bicarbonate in the blood.
- Secrete Fewer Hydrogen Ions: This reduces the removal of acid from the body.
Summary Table: Kidney's pH Regulation
| Condition | Kidney's Action | Effect on Blood pH |
|---|---|---|
| Acidic Blood | More Bicarbonate Reabsorption, More Hydrogen Ion Secretion | Increases pH |
| Alkaline Blood | Less Bicarbonate Reabsorption, Less Hydrogen Ion Secretion | Decreases pH |
