Answer:
Kidneys
Explanation:
The kidneys are the major organ of the urinary system. Kidney is not only for filtration but it also play a vital role in the urinary system.
> it helps to regulate the concentration of major ions in the body fluids.
> it helps to regulate the concentration of RBCs in the blood
> the kidney also participate with the skin and liver in regulating vitamin D
> kidneys also helps in regulating the pH of extracellular fluid.
