Suarez Susan S
Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Int J Dev Biol. 2008;52(5-6):455-62. doi: 10.1387/ijdb.072527ss.
The oviduct plays a vital role in ensuring successful fertilization and normal early embryonic development. The male inseminates many thousands or even millions of sperm, but this alone does not ensure that fertilization will be successful. The female tract, particularly the oviduct, provides filters that select for normal vigorously motile sperm. In conjunction with molecules in the seminal plasma and on sperm, the female tract regulates how and when sperm pass though the tract to reach the site of fertilization. Various regulatory processes control sperm passage into and through the oviduct. In some species, the uterotubal junction opens and closes to regulate when sperm may enter; furthermore, passage through the junction requires certain proteins on the sperm surface. Most of the sperm that manage to enter the oviduct soon become trapped and held in a reservoir. In marsupials and insectivores, this involves trapping sperm in mucosal crypts; while in most other mammalian species, this involves binding sperm to the oviductal epithelium. As the time of ovulation approaches, the sperm in the reservoir undergo capacitation, including motility hyperactivation. Capacitating sperm shed proteins that bind them to the mucosal epithelium, while hyperactivation assists the sperm in pulling off of the epithelium and escaping out of mucosal pockets. The process of sperm release is gradual, reducing chances of polyspermic fertilization. Released sperm may be guided towards the oocyte by secretions of the oviduct, cumulus cells, or oocyte. Hyperactivation likely assists sperm in penetrating the cumulus matrix and is absolutely required for penetrating the oocyte zona pellucida and achieving fertilization.
输卵管在确保成功受精和正常早期胚胎发育方面起着至关重要的作用。雄性会排出成千上万甚至数百万的精子，但仅凭这一点并不能确保受精成功。雌性生殖道，尤其是输卵管，会提供筛选机制，选择正常且活力旺盛的精子。与精浆中和精子上的分子协同作用，雌性生殖道会调节精子通过生殖道到达受精部位的方式和时间。各种调节过程控制着精子进入和通过输卵管。在一些物种中，子宫输卵管连接处会打开和关闭，以调节精子何时可以进入；此外，通过该连接处需要精子表面有特定的蛋白质。大多数成功进入输卵管的精子很快就会被困在一个储存库中。在有袋类动物和食虫动物中，这涉及将精子困在黏膜隐窝中；而在大多数其他哺乳动物物种中，这涉及将精子与输卵管上皮结合。随着排卵时间的临近，储存库中的精子会经历获能，包括运动超激活。获能的精子会脱落使其与黏膜上皮结合的蛋白质，而超激活则有助于精子脱离上皮并从黏膜小窝中逸出。精子释放的过程是渐进的，减少了多精受精的可能性。释放出的精子可能会被输卵管、卵丘细胞或卵母细胞的分泌物引导至卵母细胞。超激活可能有助于精子穿透卵丘基质，并且是穿透卵母细胞透明带并实现受精绝对必需的。
