Extraordinary organ

Any of a class of organs comprising the brain, the marrow, the bones, the vessels, the uterus, and the gallbladder, distinguished from the bowels on the grounds that they do not decompose food and convey waste and from the viscera on the grounds they do not produce and store essence. The gallbladder is an exception, because it is classed both as a bowel and as an extraordinary organ. It is considered a bowel because it plays a role in the processing and conveyance of food, and stands in exterior-interior relationship with its paired viscus, the liver. However, the bile that it produces is regarded as a clear fluid rather than as waste; hence it is also classed among the extraordinary organs.