Extracellular Acid-Base Balance

Extracellular acid-base balance refers to the regulation of the pH in the body's extracellular fluid (ECF), which is essential for maintaining normal physiological function and cellular metabolism. The ECF includes blood plasma and interstitial fluid, and its pH is tightly regulated within a narrow range (typically 7.35–7.45) to prevent protein denaturation, enzyme malfunction, and disruption of ion channels. The body uses buffer systems (bicarbonate/carbon dioxide, plasma proteins, phosphate), respiratory regulation (CO2 exhalation), and renal regulation (acid/base excretion/reabsorption) to maintain this balance. Key players include carbonic anhydrases, Na+/bicarbonate cotransporters, anion exchangers, and proton pumps. Disorders like acidemia and alkalemia arise when regulatory mechanisms fail, often due to respiratory, renal, or metabolic disturbances.