Hi,
The nephron is the functional unit of the kidney. They are responsible for the actual purification and filtration of the blood. Being part of the homeostatic mechanism of the body, the nephron helps regulate the amount of water, salts, glucose, urea and other minerals in the body. This link may be helpful: http://en.wikipedia.org/wiki/Renal_tubule#Renal_tubule
Take care and regards.
The kidneys process about 200 quarts of blood to sift out about 2 quarts of waste products and extra water. The waste and extra water become urine, which flows to your bladder through tubes called ureters. Your bladder stores urine until you go to the bathroom.