The kidneys, urinary tract, and the majority of the reproductive organs arise in the intermediate mesoderm. The kidney goes through three stages of development that mimic filogenesis (biological evolution) of the kidney; pronephros, mesonephros, and metanephros.

The pronephros arises at the C3-T1 vertebral levels by the dorsal proliferation of cords of cells. Such cords become pronephric tubules that grow caudally and get connections in order to form a common pronephritic duct that extends caudally toward the cloaca. Beyond the pronephros it is termed the Wolffian duct. The tubules of the pronephros are in continuity with the coelomic cavity. The pronephric kidney does not work in humans, but it seems to induce the normal formation of the further renal structures.

The mesonephros develops by the formation of menonephric tubules from the intermediate mesoderm of the C6-L3 vertebral levels. The tubules of...