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
Pneumatic bladder Pneumatic bladder A pneumatic bladder is an inflatable (pneumatic) bag technology with many applications. Pneumatic bladders are used to seal drains and ducts to contain chemical spills or gases. Pneumatic bladders are often used for the containment of chemical spills, oil spills or fire water on water to prevent them from entering the environment, usually in the form of booms. The Reef Ball Foundation uses a pneumatic bladder technology to float an artificial coral reef ("reef ball") into location, then deflate the bladder to sink the reef to the bottom. Pneumatic bladders, known as dunnage bags, are used to stabilize