Gonads arise from what type of mesoderm

The exact developmental pathways that guide the specification of different cell types within the mesoderm are not well understood. We have analyzed the developmental relationship between two mesodermal tissues in the Drosophila embryo, the gonadal mesoderm and the fat body. Both tissues arise from lateral mesoderm within the eve domain. Primitive gonad genital ridge develops near a mesonephric duct and a paramesonephric duct, as paired thickenings of the coelomic epithelial layer that lines the body cavity, specifically in the region that overlays the surface of the mesonephros.

Bipotential gonad, that able to adopt either male or female fate, is the first sign of development of the reproductive organs, which appears in mouse at around E Development of a testis male or an ovary female is triggered by the expression and proper function of Sry , the testis-determining gene. The primary sex cords in the male will eventually mature to become the sperm-nurturing seminiferous tubules. In the female, the primary sex cords will contribute to nurturing tissue of developing ova.

The gonad consists of germ cells and somatic cells. The primordial germ cells PGCs do not arise within the genital ridge. Thanks to the collaboration of three factors - the folding of the embryo , chemotactic factors and ameboid movements - they get from here into the wall of the intestinal tract within the embryo again and, via the dorsal mesentery, into the gonadal ridge During their migration, which takes place between the 4th and 6th weeks , they multiply through mitosis.

The primordial germ cells PGC. Like the nephrogenic cord the gonadal ridge extends from the heart region to the location near the cloaca. In the time between the 4th and 6th week the middle section of this gonadal ridge develops into a gonad anlage in that cells of the coelomic epithelium proliferate there. The immigrated PGC 14 penetrate into this thickened zone of the coelomic epithelium. The indifferent gonads thus assemble themselves from cells of various origins, whereby, as a result, the primordial germ cells and the local somatic blastema influence each other reciprocally The local coelomic mesenchyma underneath also multiplies.

The coelomic epithelium , which now becomes multi-layered, loses for now its basal membrane.