urogenital ridge

n.
  1. One of the paired longitudinal ridges developing in the dorsal body wall of the embryo, formed at first by the growing mesonephros and later by the mesonephros and the gonad.mesonephric fold Wolffian ridge
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.