Which organ is involved in regulation of all of the following: acid-base balance, blood pressure, water balance, and removal of nitrogen wastes?

The kidney plays a crucial role in the regulation of acid-base balance, blood pressure, water balance, and the removal of nitrogenous wastes, making it the correct answer.

To maintain acid-base balance, the kidneys regulate the excretion of hydrogen ions and reabsorption of bicarbonate from urine, which helps to stabilize the pH of the blood. They also influence blood pressure through the renin-angiotensin-aldosterone system; by controlling the volume of blood (through water reabsorption) and the constriction of blood vessels, the kidneys help maintain adequate blood pressure levels.

Water balance is directly managed by the kidneys as they filter blood, allowing for the reabsorption of water based on the body's hydration status. This process is crucial for maintaining homeostasis regarding fluid levels in the body.

Additionally, the kidneys are responsible for the excretion of nitrogenous wastes, such as urea and creatinine, which are byproducts of protein metabolism. Through filtration and secretion processes in the nephrons, the kidneys ensure that these potentially toxic waste products are eliminated from the body.

The liver, while essential for metabolism and detoxification, does not directly regulate these functions in the same way. The lungs regulate carbon dioxide levels for acid