Which organ is primarily responsible for the elimination of excess hydrogen ions from the body?

The kidneys are primarily responsible for the elimination of excess hydrogen ions from the body. They play a crucial role in maintaining acid-base balance by regulating the concentration of hydrogen ions in the blood. This regulation involves the filtration of blood, reabsorption of bicarbonate, and secretion of hydrogen ions into the urine.

When the body is in a state of acidosis, where there is an excess of hydrogen ions, the kidneys respond by increasing the secretion of these ions into the urine while retaining bicarbonate, which helps to buffer the acidity. This process effectively helps to neutralize excess acids and maintain the pH within a narrow, optimal range essential for various biochemical processes.

Other organs, such as the lungs, primarily help in the regulation of carbon dioxide levels, which indirectly influences hydrogen ion concentration through the carbonic acid-bicarbonate buffer system. While the liver is involved in metabolic processes and detoxification, it does not directly eliminate hydrogen ions. The heart's function is to pump blood and does not play a role in hydrogen ion regulation. Therefore, the kidneys are the key organ in directly managing the body's hydrogen ion levels.