In the 6th week, the primordial germ cells infiltrate into both gonadal ridges. The primordial germ cells become surrounded by the coelomic epithelial cells that have proliferated and advanced into the depths of the mesenchyma. These germinal cords are still connected with the surface of the coelomic epithelium. At this point, the male and female gonadal primordia cannot be distinguished and, for this reason, this condition is referred to as the indifferent gonadal primordium.
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Commentary
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The gonads (= gonadal ridge + primordial germ cells) are extended, arched bodies in the somatic cavity.
Their cranial and caudal parts later form themselves back into gonadal ligaments, while the remainder proliferates further to testis and ovary, which soon exceeds the mesonephros in size.
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