Acid-base Balance

Abstract

The acid-base systems function is to maintain the blood and intracellular pH within a narrow range with normal, increased or decreased metabolic acid production and excretion rates. The usual end point of metabolism is the production of an acid, primarily carbonic acid (H₂CO₃) as well as sulfuric, phosphoric and small amounts of organic acids. The pH is regulated by physiologic buffers, by production of base (primarily bicarbonate) and by control of acid excretion by the lungs and kidneys. The primary volatile acid, H₂CO₃ is excreted as CO₂ by the lungs and as H₊ and ammonium ion (NH₄₊) by the kidneys. Fixed acids such as sulfuric, phosphoric and the organic acids are excreted by the kidneys. Carbonic acid and bicarbonate amount balance in the blood must be maintained at a constant ratio of 1:20 in order to keep the plasma’s hydrogen ion concentration at a constant value (pH 7.4).