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mesonephros mes·o·neph·ros (měz'ə-něf'rəs, -rŏs', měs'-)
n. pl. mes·o·neph·roi (-něf'roi')
The second of the three excretory organs that develop in a vertebrate embryo, replaced by the metanephros in higher vertebrates. Also called wolffian body.
permanent kidney of amphibians and most fish, developing posterior to and replacing the pronephros of the embryonic and larval stages. It is a paired organ consisting of a set of nephrons having capsules that filter blood from the glomerulus and tubules whose cells reabsorb water and nutrients and secrete nitrogenous wastes. Glomeruli are absent in some marine fish; urine then forms solely in the tubules, a process that conserves water. The tubules empty into a long tube, the Wolffian duct, a remnant of the pronephros. In more advanced vertebrates the mesonephros develops in the embryo but is replaced after the 10th week in humans by the metanephros.