Final answer:
The kidneys control acid-base balance by secreting varying amounts of substances. They excrete less bicarbonate in urine when the blood pH is low and more bicarbonate when the blood pH is high. The kidneys also help maintain homeostasis by controlling the volume of extracellular fluids.
Step-by-step explanation:
The kidneys play a vital role in regulating the acid-base balance in the body by secreting varying amounts of substances. When the blood pH is too low, the kidneys excrete less bicarbonate, which is basic, in the urine. Conversely, when the blood pH is too high, the kidneys excrete more bicarbonate in the urine.
Additionally, the kidneys assist in maintaining homeostasis by controlling the volume of extracellular fluids, including the blood, through the excretion of salt and water.