The kidneys filter blood and remove waste to produce urine, which travels through thin tubes called ureters to the bladder. The bladder stores urine until it is full, at which point the body signals that it is time to urinate and the urine exits through the urethra. The urinary system works to filter waste from the bloodstream, transport urine from the kidneys to the bladder for storage, and then expel urine from the body.