– Acids and bases are constantly produced in the body by various cellular activities. However, the pH of the body fluids is maintained within a narrow range by buffer mechanisms.

– Buffering mechanisms can maintain a constant pH only temporarily and function effectively only when there are mechanisms for excretion of excess acids and bases from the body

– Buffer and excretory systems maintain acid-base balance

– Lungs regulate blood pH by excreting CO2

– Kidneys regulate blood pH by excreting hydrogen and bicarbonate ions

– Other buffer systems: Proteins (absorb excess H+) & phosphate (controls intracellular pH)