Dialysis is a process of assisting kidneys do what they normally do, which is remove nitrogenous wastes that are a by product of various body processes. Sometimes the kidneys either decrease their ability to perform this function, or shut down altogther in their ability to remove wastes in the form of urea. A dialysis machine removes the blood from the patient and filters it through a semipermeable membrane, with the blood on one side and a substance which serves as a dysilate on the other, which helps the waste products diffuse across the membrane. The dysilate then goes to a waste receptacle while the cleansed blood is returned to the patient. Kidneys normally remove wastes in the form of urea by filtering the blood through a series of nephrons, which are fan-shaped structures inside the kidney. The waste is combined with a little water to keep it in a liquid format and transferred to a slender tube called a ureter, which transfers the urine to the urinary bladder. While dialysis machines serve an invaluable service to those with decreased or nonexistent kidney function, they are unable to perform the kidneys endocrine functions, which are to maintain water balance and provide important substances necessary for red blood cell production and bone production.