Kidney always so simple; in cartilaginous fish and some amphibians, there is also a shorter duct, similar to the amniote ureter, which drains the posterior (metanephric) parts of the kidney, and joins with the archinephric duct at the bladder or cloaca. Indeed, in many cartilaginous fish, the anterior portion of the kidney may degenerate or cease to function altogether in the adult. In the most primitive vertebrates, the hagfish and lampreys, the kidney is unusually simple: it consists of a row of nephrons, each emptying directly into the archinephric duct. Invertebrates may possess excretory organs that are sometimes referred to as
Tube cleaning to deposits which may also cause tube failure. Depending on application, conveying medium and tube material, the following methods of tube cleaning are available: In medical field, "lost" tubes are tubes which have to be replaced after single use. This is not genuine tube cleaning in the proper sense and is very often applied in the medical sector, for instance with cannulas of syringes, infusion needles or medical appliances, such as kidney machines at dialysis. The reasons for the single use are primarily the elimination of infection risks but also the fact that cleaning would be very expensive and, particularly