Desjardins C
J Anim Sci. 1978;47 Suppl 2:56-79.
Sexual development is an ordered process that begins at the moment of fertilization and terminates with the production and transfer of viable gametes. The formation of the male gonad depends upon genes located on both sex chromosomes and autosomes. Differentiation and growth of the male reproductive system is directed by the fetal testis through the production of a putative peptide which causes the regression of the Mullerian ducts and the secretion of testosterone which virilizes the Wolffian duct and thereby directs the differentiation of the internal accessory structures of reproduction. A third hormone, dihydrotestosterone, is synthesized intracellularly from testosterone within the urogenital sinus and tubercle. The action of this hormone controls the formation of the prostate and the external genitalia characteristic of the male phenotype. The postnatal growth of the testis and accessory sex tissues follows a characteristic curvilinear pattern with the most prominent increments coincident with the onset in testosterone production. Spermatogonial differentiation may proceed in the absence of hypophyseal or gonadal hormones but the respective maturation divisions of primary and secondary spermatocytes and the completion of spermiogenesis are clearly dependent upon testicular steroids produced under the influence of LH. Germ cells differentiate in a unique environment created, in part, by the blood testis barrier which arises as a result of tight-junctional complexes formed between adjacent Sertoli cells. Sertoli cells actively secrete fluids and export an androgen binding protein under the influence of androgens and FSH. Maintenance of spermatogenesis depends on high intratubular concentrations of testosterone, provided in part by the steroidogenic actions of LH on the Leydig cell and, in part, by the production of androgen binding protein by the Sertoli cell. Thus, both gonadotropins act in concert to maintain germ cell production. Selective removal of either LH or FSH curtails sperm production but testosterone supplementation, in adequate amounts, allows spermatogenesis to proceed in the absence of the pituitary gland.
性发育是一个有序的过程，始于受精之时，止于有活力配子的产生和传递。雄性性腺的形成取决于位于性染色体和常染色体上的基因。雄性生殖系统的分化和生长由胎儿睾丸通过产生一种假定的肽来引导，该肽导致苗勒管退化，以及分泌睾酮，睾酮使沃尔夫管男性化，从而引导内部附属生殖结构的分化。第三种激素，双氢睾酮，在泌尿生殖窦和结节内由睾酮在细胞内合成。这种激素的作用控制前列腺的形成和男性表型特有的外生殖器的形成。睾丸和附属生殖组织的出生后生长遵循一种特征性的曲线模式，最显著的增长与睾酮分泌开始时一致。精原细胞的分化可以在没有垂体或性腺激素的情况下进行，但初级和次级精母细胞各自的成熟分裂以及精子发生的完成显然依赖于在促黄体生成素影响下产生的睾丸类固醇。生殖细胞在一个独特的环境中分化，部分是由血睾屏障形成的，血睾屏障是相邻支持细胞之间形成紧密连接复合体的结果。支持细胞在雄激素和促卵泡生成素的影响下积极分泌液体并输出雄激素结合蛋白。精子发生的维持取决于管内高浓度的睾酮，部分由促黄体生成素对睾丸间质细胞的类固醇生成作用提供，部分由支持细胞产生雄激素结合蛋白提供。因此，两种促性腺激素协同作用以维持生殖细胞的产生。选择性去除促黄体生成素或促卵泡生成素会减少精子产生，但适量补充睾酮可使精子发生在没有垂体的情况下继续进行。
