ABSTRACT
The urinary and genital systems are closely associated in their development. Both arise from the intermediate mesoderm. In the human, two nephric structures, the mesonephros and metanephros, as temporary and permanent excretory organs respectively, arise during development (the concept of pronephros does not apply in humans). Development of the urinary system depends on directed growth and mutual inductive influence of different structures. Committed mesenchymal cells, under the influence of signals from the extracellular matrix, proliferate and form nephrogenic cords (urogenital ridges) on both sides of the aorta. Mesonephric tubules form in the ridge and gain connection to the mesonephric duct. The mesonephric duct opens into the cloaca.
