Sex cords
In embryogenesis, the sex cords, are structures that develop from the gonadal ridges. After sexual differentiation, at day 49, the sex cords in males become the testis cords by the action of the testis-determining factor protein, which helps to develop and nourish the Sertoli cells. The testis cords are precursors to the rete testis. They play several different roles in the development of the male genitals.
In females the sex cords become the cortical cords, also called secondary cords. After further development they become the ovarian follicles.
The primitive sex cords originate from the proliferation of the epithelium of the two gonadal ridges. These epithelial cells will penetrate and invade the underlying mesenchyme to form the primitive sex cords. This occurs shortly before and during the arrival of the primordial germ cells to the paired gonadal ridges.
