Here's why:

* Filtering blood: The kidneys are responsible for filtering waste products and excess fluids from the blood.

* Producing urine: The filtered waste products and fluids are then combined to form urine.

* Regulating electrolytes: The kidneys play a crucial role in maintaining the body's electrolyte balance.

* Producing hormones: The kidneys produce hormones like erythropoietin (stimulates red blood cell production) and renin (regulates blood pressure).

While the urinary system includes other organs like the bladder, ureters, and urethra, the kidneys are the primary organs responsible for its function.