The urinary system, or renal system, is responsible for filtering blood, regulating fluid and electrolyte balance, and excreting metabolic wastes as urine. Its primary organs are the kidneys, ureters, urinary bladder, and urethra. The kidneys filter blood to form urine, reabsorb needed substances, and secrete waste products like urea. This system is critical for maintaining blood pressure, pH balance, red blood cell production (via erythropoietin), and overall homeostasis.