Which organ assists in regulating the acid-base balance of the circulatory system by producing bicarbonate?

• A. Kidneys
• B. Skin
• C. Lungs
• D. Liver

Answer: (A)

Bicarbonate production to regulate acid-base balance is primarily a kidney function. The kidneys maintain the blood’s bicarbonate pool by reabsorbing filtered bicarbonate and, when needed, generating new bicarbonate. They do this through tubular processes that convert other substances (like glutamine) into bicarbonate while excreting hydrogen ions in urine. This replenishes the bicarbonate buffer in the blood, helping neutralize acids and stabilize pH.

The lungs help control pH too by removing carbon dioxide, which shifts the acid-base balance, but they don’t produce bicarbonate themselves. Other organs, like the skin or liver, don’t contribute bicarbonate in meaningful amounts for this purpose.