Which organ plays a primary role in regulating acid-base balance by excreting excess H+?

The kidney plays a crucial role in maintaining the body's acid-base balance primarily by excreting excess hydrogen ions (H+) into the urine. This process involves the regulation of bicarbonate levels as well. When the blood becomes too acidic, the kidneys help to excrete more H+ and retain bicarbonate, which acts as a buffer to neutralize acidity in the blood.

The process of renal regulation of acid-base balance is slow in comparison to respiratory control, but it is essential for long-term regulation. The kidneys adjust the amount of H+ excreted based on the body's needs and the prevailing pH of the blood. In cases of acidosis, the kidneys conserve bicarbonate ions and excrete more hydrogen ions. Conversely, in alkalosis, they might excrete bicarbonate and retain H+ to restore balance.

In contrast, while the liver, lungs, and pancreas contribute to the overall metabolism and homeostasis of the body, they do not directly regulate acid-base balance as significantly as the kidneys. The liver metabolizes nutrients and produces various substances, while the lungs primarily manage acid-base balance through carbon dioxide regulation. The pancreas's main functions relate to digestion and hormone production rather than direct involvement in acid-base balance regulation.