metanephros /-nef″rəs/ pl. metanephra, metanephroi [Gk, meta + nephros, kidney] , the third, and permanent, excretory organ to develop in the vertebrate embryo. It consists of a complex structure of secretory and collecting tubules that develop into the kidney. In most mammals there is limited functional use of the metanephric kidney during fetal life because waste materials are transferred across the placenta to the mother for elimination. Also called hind kidney. See also kidney, mesonephros, pronephros.
