The most caudally located of the three excretory organs appearing in the evolution of the vertebrates (the others being the pronephros and the mesonephros); in mammalian embryos, the m. develops caudal to the mesonephros during its regression, becoming the permanent kidney. SYN: hind kidney. [meta- + G. nephros, kidney]
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meta·neph·ros -'nef-rəs, -.räs n, pl -neph·roi -.rȯi either member of the final and most caudal pair of the three successive pairs of vertebrate renal organs that functions as a permanent adult kidney in reptiles, birds, and mammals but is not present at all in lower forms compare MESONEPHROS, PRONEPHROS
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n.
the excretory organ of the fetus, which develops into the kidney and is formed from the rear portion of the nephrogenic cord. It does not become functional until birth, since urea is transferred across the placenta to the mother.
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meta·neph·ros (met″ə-nefґros) pl. metanephґroi [meta- + Gr. nephros kidney] the primordium of the permanent kidney, developing later than and caudal to the mesonephros, from the mesonephric duct and nephrogenic cord. Called also definite, definitive, or hind kidney. metanephric adjMedical dictionary. 2011.