Anatomy and Physiology II Practice Test

Which substance can the kidney remove that the lung cannot, aiding in pH regulation?

1. Acids

2. Bases

3. Hydrocarbons

4. Gases

The correct answer is: Bases

The kidney plays a crucial role in maintaining the body's pH balance through the regulation of bicarbonate (HCO₃⁻) and hydrogen ions (H⁺). Specifically, the kidneys are able to reabsorb bicarbonate from urine or excrete hydrogen ions into the urine, facilitating the regulation of acid-base balance in the body. This capability is essential for the precise control of blood pH, which can be impacted by various metabolic processes. While the lungs contribute to pH regulation by controlling the exhalation of carbon dioxide (a product of metabolism that combines with water to form carbonic acid), they do not have the ability to directly excrete bases or acids in the manner that kidneys do. The renal system can selectively excrete or retain substances, thereby adjusting the blood's acid-base status more directly through its tubular secretions and reabsorption processes. This unique function underscores the kidneys' importance in pH regulation, particularly in handling excess acids or bases that may accumulate in the body due to metabolic activity or disorders. In summary, the kidney’s ability to manage bases through bicarbonate reabsorption or hydrogen ion excretion is a vital aspect of its role in maintaining the acid-base homeostasis that the lungs are not equipped