Which two body systems contribute to acid-base balance of blood?

The two body systems that regulate the pH of the blood are the lungs and the kidneys. The lungs regulate the pH through breathing out the carbon dioxide. Since CO₂ is acidic, when it is accumulated in the body, the pH of blood increases. Hence, the lungs control the speed and depth of breathing. The kidneys regulate pH by filtering out the salts in our blood which makes the blood also acidic. The filtered waste are excreted out of the body as urine.