text: The<unk>  is a part of the prenatal development, and concerns the<unk>  system and sex<unk> . The latter is a part of the stages of sexual differentiation.
  The<unk>  and reproductive<unk>  are developed from the intermediate mesoderm. The permanent<unk>  of the adult are preceded by a set of structures which are purely embryonic, and which with the exception of the ducts disappear almost entirely before the end of fetal life. These embryonic structures are on either side; the pronephros, the mesonephros and the metanephros of the kidney, and the Wolffian and Müllerian ducts of the sex<unk>  The pronephros disappears very early; the structural elements of the mesonephros mostly degenerate, but the gonad is developed in their place, with which the Wolffian duct remains as the duct in males, and the Müllerian as that of the female. Some of the tubules of the metanephros form part of the permanent kidney.
option_0: Development of the urinary and reproductive organs
option_1: Kidney development
option_2: Human embryogenesis
option_3: Eye development
option_4: Prenatal development
option_5: Female reproductive system 
option_6: Causes of umbilical region pain
option_7: Limb development