Three-dimensional architecture of the ovine oviductal mucosa

The objective of this work was to establish for the first time a complete three-dimensional model of the ovine oviductal mucosa. The oviducts of 15 cyclic ewes were examined combining the direct examination of the mucosa, by scanning electron microscopy (SEM) and histology, with the SEM observation of resin moulds of the oviductal lumen. Around the ostium abdominale, all longitudinal primary folds and wide secondary are seen to form cul-de-sacs, with their opening pointing in the ovarian direction were observed. At the connection of the ampulla to the isthmus, there is a sharp change in the morphology, from a high folded structure to a smoother one. In the utero-tubal junction, the primary folds broaden and become more voluminous, the lumen has a slit-like appearance, and secondary folds form cul-de-sacs with their opening oriented towards the uterus. The areas between the folds throughout the lumen of the oviduct show a high degree of complexity. The presence of crypts was observed in all the regions studied, branched in the ampulla and spiniform in the isthmus. Marked variations were observed in the oviductal epithelium depending on the oviductal segment and the basal or apical areas of the folds. The variations found regarding the phase of the oestrous cycle were similar to those described in studies of other species. The anatomy of the oviductal mucosa provides a complex system that seems to be designed to regulate the movement of fluids and the passage of cells within the oviductal canal.