The oviducts of 31 cyclic cows were examined to study the structure and nature of the oviductal mucosa. The general distribution of spermatozoa within the oviductal mucosa was studied in five additional cows. The oviductal infundibulum is an asymmetric funnel-shaped structure surrounding the ostium. It is divided along the free boarder of the mesosalpinx and presents one wide and one narrow side. The mucosa of the wide side possesses a system of low interconnected cords that converge distally forming primary folds. The folds on the narrow side start sharply from the free margin and fuse toward the ostium abdominale. Areas between folds throughout the lumen of the oviduct show a high degree of complex organization. Interfold spaces are occupied by secondary and small interconnected folds which join to form a system of cul-de-sacs. In the infundibulum, these cul-de-sacs open toward the ovary, while cul-de-sacs present in the caudal isthmus and in the UTJ open toward the uterus. Marked variations were observed in the oviductal epithelium depending on the oviductal segment, basal or apical areas of the folds, and phase of the oestrous cycle. Near to the time of ovulation, numerous spermatozoa were found in the periphery of the caudal isthmus within pockets of basal interfold areas, as well as within pockets and cul-de-sacs of the tubo-uterine junction. Individual spermatozoa were also observed in peripheral areas of the ampullary-isthmic junction and ampulla. The topography of the oviduct provides a complex system of regulation which may influence not only the passage of gametes and/or embryos, but also movement of fluid within the oviductal canal.
Copyright 2000 Wiley-Liss, Inc.