Icon module 21

Anatomic relationship between the genital and urinary systems

The development of the genital apparatus accompanies that of the urinary system (formation of the urinary apparatus). It also has its origin in the intermediate mesoderm (stage 9) and urogenital sinus (stage 15). The primordial germ cells (stage 7) share in the formation of the gonads, but have an ectodermal origin (stage 3). In males, the development of the testes is closely tied with that of the mesonephros. In females, on the other hand, the mesonephros plays no role at all.

Color code for the genital tract module
Color code for the genital tract module
Paramesonephros, Müller, etc.:
Mesonephros, Wolff, etc:
Sinus urogenital, entoblaste, etc:


The intermediate mesoblast is the origin of an elongated structure, the urogenital ridge (crista urogenitalis), which lies on both sides of the midline between the lateral mesoderm and the root of the dorsal mesenterium of the embryo. It consists of two main components, the nephrogenic cord, out of which the urinary apparatus arises and the genital ridge (stage 14) as the origin of the gonads. The genital ridge extends from the upper thorax region to the level of the cloaca. The true gonad anlage develops, though, out of only the middle area.
The cranial and caudal parts of the urogenital ridge form the upper and lower gonadal bands, respectively, that as embryonic structures secure the gonads cranially and caudally (more info: the development of the ligaments).

Fig. 3 - Sexually indifferent embryo
Migration of the primordial germ cells into the genital ridge

  1. Coelomic epithelium
  2. Local mesenchyma (in proliferation)
  3. Gonadal cord
  4. Primordial germ cells (PGC)
  5. Mesenchyma
  6. Allantois
  7. Omphalomesenteric duct
  8. Intestine
  9. Dorsal mesentery
  10. Genital ridge
  11. Nephrogenic cord
  12. Mesonephric duct (Wolff)
  13. Mesonephric tubule
  14. Aorta

Fig. 3

Small picture:
Anlage of the genital ridge at 5 weeks.

Main picture: development of the indifferent gonad with the migration of primordial germ cells (PGC) at around the 6th week.

Note! The module's color code is not used in this diagram.