Explain more in simple terms how kidney regulates acid, base balance

• When the body is too acidic (low pH), the kidneys secrete more $H^+$ into the urine to remove acid and reabsorb more $HCO_3^-$ back into the blood to buffer the acid.
• When the body is too alkaline (high pH), the kidneys reabsorb less $HCO_3^-$ (allowing it to be excreted) and secrete less $H^+$ (or even reabsorb it) to conserve acid.

This selective secretion and reabsorption primarily occur in the distal convoluted tubule and collecting duct of the nephron, ensuring that blood pH remains stable.