Today's Word of the Day means...
metanephros met·a·neph·ros (mět'ə-něf'rəs, -rŏs')
n. pl. met·a·neph·roi (-roi')
The third and final excretory organ that develops in a vertebrate embryo. In birds, reptiles, and mammals it replaces the mesonephros as the functional excretory organ and develops into the adult kidney.
permanent kidney in reptiles, birds, and mammals, developing by the 10th week in human embryos from the lower part of the Wolffian duct, and replacing the embryonic structure called the mesonephros. It consists of a compact, paired organ containing many nephrons; a ureter separate from the Wolffian duct leads from the metanephros to the bladder.