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a longitudinal dorsolateral tract of intermediate mesoderm; the primordium for both mesonephric and metanephric tubules.
either of the paired longitudinal ridges of tissue that lie along the dorsal surface of the coelom in the early developing vertebrate embryo. It is formed from the fusion of the nephrotome tissue and gives rise to the structures making up the embryonic urogenital system. See also mesonephros, metanephros, pronephros.