Oviduct function in cows and pigs: With special reference to sperm capacitation
Rodriguez Martinez, H.
Asian-Australasian Journal of Animal Sciences 14(Special Issue): 28-37
2001
ISSN/ISBN: 1011-2367 Document Number: 507982
In cows and pigs, the oviduct is the place where sperm transport is ultimately regulated to facilitate normal fertilization of the ovulated oocyte/s. To pursue this function, the organ contains a particular segment, the sperm reservoir, which ensures the storage of spermatozoa with maintained viability and fertilizing capacity. Experimental evidence indicates the process of sperm capacitation is delayed in the sperm reservoir during the lengthy pre-ovulatory oestrus that characterizes these species, by interactions between spermatozoa, the luminal epithelium and the tubal secretion. Sperm capacitation seems to be, however, facilitated by the tubal fluid at the upper segments, when spermatozoa are sequentially released from the reservoir, in relation to ovulation and imminent gamete encounter. One of the roles of the oviduct is thus to reduce the numbers of these potentially fertile spermatozoa being released from the reservoir to physiological figures when they encounter the oocyte/s, thus lowering the chances for lethal polyspermia to occur. The oviduct is also responsible for the effective pick-up of the newly ovulated oocyte/s, as well as oocyte transport and final maturation of the zona pellucida, offering -as such- the best milieu for gamete interaction during fertilisation. Following the formation of the zygote/s, the oviduct controls the transport of the early embryo/s to a synchronous, hormonally well-prepared secretory endometrium, facilitating further development of the conceptus/es. Oviductal function depends on the concerted action of its muscle wall, its lining epithelium and the intraluminal fluid where gametes and embryos bathe in. Such interactions are modulated by a proper endocrinological interplay and any deviations concur to impair fertilisation, allowing lethal polyspermia or asynchrony in embryo transport to occur, ultimately resulting in infertility. This overview of oviduct structure and function addresses particularly sperm capacitation and fertilisation in vivo, in an attempt to describe possible reasons behind failures seen during in vitro fertilisation (IVF), a yet unsolved problem in the establishment of reproductive biotechnologies in domestic farm animals.