The human body maintains pH balance by regulating the levels of acid and base in the body. This is done through a variety of mechanisms, including the kidneys, lungs, and digestive system. The kidneys help to regulate the acid-base balance by excreting excess acids or bases in the urine. The lungs help to regulate the acid-base balance by exhaling carbon dioxide, which is an acid. The digestive system helps to regulate the acid-base balance by breaking down food into its component parts and releasing acids or bases into the bloodstream.