Which of the following structures helps regulate the pH of blood?

The kidneys play a crucial role in regulating the pH of blood by managing the excretion and reabsorption of hydrogen ions and bicarbonate. They help maintain the acid-base balance by either excreting excess acids or bases or reabsorbing them back into the bloodstream as needed. This process ensures that blood pH remains within the narrow range necessary for optimal physiological function, typically between 7.35 and 7.45.

While the liver, spleen, and thymus have important roles in other bodily functions, they do not directly regulate blood pH in the same manner as the kidneys. The liver is primarily involved in metabolism, detoxification, and the synthesis of proteins, while the spleen is mainly responsible for filtering blood and recycling iron from red blood cells. The thymus is essential for immune function, particularly in T-cell maturation but does not have a direct impact on blood pH regulation.