How do the kidneys regulate pH in the body?

The kidneys play a crucial role in maintaining the body's acid-base balance, primarily through the processes of excreting hydrogen ions and reabsorbing bicarbonate. When the blood becomes too acidic, the kidneys will excrete excess hydrogen ions into the urine. This action helps to reduce the acidity of the blood by removing acid. Simultaneously, the kidneys reabsorb bicarbonate from the urine back into the bloodstream. Bicarbonate acts as a buffer that can neutralize excess acid in the body.

This dual function of excreting hydrogen ions and reabsorbing bicarbonate allows the kidneys to effectively manage the blood’s pH levels, maintaining homeostasis within the body. This regulatory mechanism is essential for various bodily functions, including enzyme activity and overall metabolic processes. Thus, the explanation highlights why this particular choice is the correct one for understanding how the kidneys contribute to pH regulation in the body.