The Excretory system is responsible for the elimination of wastes produced by homeostasis. There are several parts of the body that are involved in this process,such as sweat glands,the liver,the lungs and the kidney system. Since we are focusing on the formation of urine within the kidneys, we will simply overviewing the kidney's role in excretion.
Every human has two kidneys.
The blood arrives at the kidney via the renal artery,which splits into many afferent arterioles. These arterioles go to the Bowman's Capsules of nephrons,where the wastes are taken out of the blood by pressure filtration. Peritubular capillaries also surround the nephron so substances can be taken in and out of the blood. The renal cortex is the outer layer of the kidney and the medulla is the inner layer of the kidney. The renal pelvis takes urine away from the kidney via the ureter.