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试述下丘脑—垂体—性腺轴的主要生殖激素如何调控精子的发生与发育

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正确答案:

睾丸的正常机能受下丘脑-垂体-睾丸系统自上而下的正向调节和自下而上的反馈调节, 共同维持精子的发生。

1、自上而下的正向调节下丘脑脉冲释放的 GnRH经垂体门脉送入垂体,促进垂体 LH和 FSH的合成和释放,并进入血液循环运送到睾丸。其中 LH刺激睾丸间质细胞产生雄激素,主要是睾酮。睾酮可直接进入血液循环促进雄性第二性征、副性腺、生殖管道和性行为的维持和发育;睾酮还可进入精细管维持精子的发生。 FSH作用于足细胞可产生雄激素结合蛋白 (ABP),并分泌抑制素。 ABP能和睾酮形成一种复合物与精子共同进入附睾,满足正常功能对高浓度睾酮的需要;同时,精子细胞的成熟及精子释放也需要相当水平的睾酮。

2 、自下而上的反馈调节睾酮可通过负反馈抑制下丘脑 GnRH和垂体 FSH、 LH的分泌;抑制素可通过血液以负反馈抑制垂体FSH的分泌,但对 LH无抑制作用。论述深入系统

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