Читать книгу New Concepts for Human Disorders of Sexual Development - Группа авторов - Страница 29

The undifferentiated gonadal anlagen in XY individuals show the first signs of testicular development at day 42 pc. This critical event is referred to as sex determination. As described above, it is related to the expression of the testis determining gene SRY, followed by expression of SOX9 (for details see online suppl. table 1). Gonocytes in the testis primordium proliferate rapidly by mitoses and subsequently become quiescent without entering meiosis. Morphogenesis of the testis is apparent when Sertoli cells supported by PTC form testicular cords, also hosting the gonocytes. The morphology of the testes remains stable until puberty when the cords are differentiated into seminiferous tubules at the beginning of spermatogenesis. Activation of the spermatogenic process results in an increase of the testicular volume; this observation is used as a clinical definition of the onset of puberty in boys. When looking at the tissue level, this is reflected by quantitative onset of meiotic activity of testicular germ cells and formation of a lumen shifting the seminiferous cords to tubules.