The Thai Journal of Veterinary Medicine


Paisan Tienthai


In the pig, sperm transport is regulated, to facilitate normal fertilization of the ovulated oocytes, by the oviduct which contains a particular segment, the sperm reservoir. The main function of the sperm reservoir is to ensure that stored spermatozoa have maintained viability and fertilizing capacity. The process of sperm capacitation is delayed in the sperm reservoir, during the lengthy pre-ovulatory estrus by interactions between the spermatozoa, the oviduct epithelium and secretion products. Sperm capacitation seems to be facilitated by the tubal fluid in the upper segment of the oviduct releasing sperm from the reservoir in relation to the time of ovulation. One of the roles of the oviduct is to reduce the numbers of fertile spermatozoa being released from the reservoir before they encounter the oocytes, thus decreasing the chances of polyspermy. The function of the oviduct depends on the concerted action of its smooth muscle wall, lining epithelium and tubal fluid which bathe the gametes and embryos. Such interactions are modulated by a suitable hormonal interplay and any deviations combine to impair fertilization, allowing lethal polyspermy or asynchrony in embryo transport, eventually resulting in infertility. This review of the oviduct structure and function particularly addresses sperm capacitation and fertilization in vivo, in an attempt to describe some possible reasons behind failures seen during in vitro fertilization (IVF), a substantial problem in reproductive biotechnology in farm animals.



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