EXCRETORY PROCESS

Trough the renal artery. The blood charged with toxic substances reaches the kidneys. In this way, the waste that carries blood is retained in the kidney and urine is formed. 

Then the urine passes through the urinary tract. The ureters are two tubes that leave one of each kidney and go to the urinary bladder. For them carry urine formed in the kidneys. The blood leaves the kidney through the renal vein. 

It no longer contains urea or uric acid, but it still has carbon dioxide. For that reason it passes to the vena cava and from there to the heart to finally go to the lungs.