Urinary system diagram – The urinary system, also referred to as renal system, consists of the kidneys, bladder, urethra and ureters. Each kidney consists of millions of functional units. Urinary system primary purpose is to remove waste from the body (urea and uric acid) as well as to regulate electrolyte balance (e.g. sodium, calcium and potassium), regulate acid-base homeostasis and maintain blood pressure. The urinary system diagram below with labels shows the various parts of this system.