The urinary system is composed of the kidneys, ureters, urinary bladder, and urethra. The kidneys filter around 180 liters of blood per day to produce around 1-2 liters of urine, removing waste and regulating fluid, electrolyte, and acid-base balance. The basic functional unit of the kidney is the nephron, which filters blood to form urine. The ureters then transport urine from the kidneys to the urinary bladder, a temporary storage organ. From here, urine exits the body through the urethra upon voluntary muscle control. Together these organs work to maintain homeostasis by filtering waste from the blood and regulating fluid balance.