Acid–Base Physiology

  • Alluru S. ReddiEmail author


Acid–base physiology deals with the maintenance of normal hydrogen ion concentration (abbreviated as [H+]) in body fluids. The normal [H+] in the extracellular fluid is about 40 nmol/L or 40 nEq/L (range 38–42 nmol/L), which is precisely regulated by an interplay between body buffers, lungs, and kidneys. Since many functions of the cell are dependent on the optimum [H+], it is extremely important to maintain [H+] in blood ~ 40 nmol/L. Any deviation from this [H+] results either in acidemia ([H+] > 40 nmol/L) or alkalemia ([H+] < 40 nmol/L). This chapter provides an overview of the role of buffers, lungs, and kidneys in regulating [H+] in body fluids. The [H+] in blood is so low that it is not measured routinely. However, the [H+] is measured as pH, which is expressed as \( \text{pH}=-\log \,[{{\text{H}}^{\text{+}}}] \). Thus, pH is defined as the negative logarithm of the [H+]. An inverse relationship exists between pH and [H+]. In other words, as the pH increases, the [H+] decreases and vice versa. Cells cannot function at a pH below 6.8 and above 7.8. The normal arterial pH ranges from 7.38 to 7.42, which translates to a [H+] of 38–42 nmol/L. Blood pH is under constant threat by endogenous acid and base loads. If not removed, these loads can cause severe disturbances in blood pH, and thus impair cellular function. However, three important regulatory systems prevent changes in pH and thus maintain blood pH in the normal range. These protective systems, as previously stated, are buffers, lungs, and kidneys.


Acid–base physiology Production of endogenous acids Production of endogenous bases Maintenance of normal pH Urinary acidification 

Suggested Reading

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Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  1. 1.Department of Medicine Division of Nephrology and HypertensionRutgers New Jersey Medical SchoolNewarkUSA

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