The kidneys have an important role to play in homeostasis in humans. They filter out the urea, and excess minerals in the blood. They use up some glucose to power this process but they do nothing to the proteins in the blood.
1. Renal Artery - blood flows into the kidney
2. Renal Vein - "treated" blood flows out.
3. Pelvic Sac - where the urea and some minerals are deposited.
6. Ureter - takes the urea etc... to the bladder.