Ovary

Differentiation of the ovary does not involve TDF and represents the uninfluenced developmental pathway. At S20, the ovary is morphologically distinguishable from the testicle for the first time. The first discernible difference is the absence of testicular cords. The primordial gonadal cords become shifted toward the periphery. In this way, a cortical layer (cortex ovarii) and a medullary zone (medulla ovarii) can be seen. The germ cells lie mainly in the cortex, and only a few gonadal cords reach the less developed medulla. In the region of the hilum, the ovarian rete arises, i.e. a network of mesenchymal cells connected to the mesonephros.
From week 12 onward, an increasing number of oogonia with synchronous mitoses are observed in the cortical layer. The oogonia produce clones, similar to the spermatogonia: individual cells are interconnected by cell bridges.