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
Urinary bladder (Chinese medicine) Urinary bladder (Chinese medicine) As distinct from the Western medical concept of Urinary bladder, this concept from Traditional Chinese Medicine is more a way of describing a set of interrelated functions than an anatomical organ. (See Zang Fu theory) The Bladder is a Yang (Fu) organ; its paired Yin (Zang) organ is the Kidney. Both are associated with the element of water and the emotion of fear. As opposed to western medicine, where the bladders function is the storage and excretion of urine, the bladder in Traditional Chinese Medicine has extended functions, including how fluids are transformed during urine production.