The kidney is the organ of the urinary system where urine is produced. Urine is transported to the bladder by the ureters. It is finally eliminated from the organism through the urethra.
Urine contains blood waste (urea, creatine, certain medications, etc).
It is at the level of the nephron of the kidney where the waste passes from blood to urine.
Click on to view a section of a kidney and a nephron.