Morphohistological characteristics of rabbit oviduct: a proposal for a single regionalization

In rabbits, like other mammals, there are proposals for the oviduct regionalization. Reports consider different regions with inconsistent tissue characteristics, which make it difficult to compare results between studies. Our aim was to analyze morphohistological characteristics of the rabbit oviduct, such as thickness of epithelium, proportion of secretory or ciliated epithelial cells, presence of submucosa or crypts, shape of transverse sections, and thickness of smooth muscle layer, in order to identify regions and discriminate the possible limits between them. To do this, Masson's thricrome was used to identify tissue characteristics along the oviduct. Both qualitative and quantitative analyses were performed. Additionally, Mann-Whitney-U or Kruskall-Wallis tests were used to determine significant differences (P ≤ 0.05) for variables between oviductal regions. Five regions were well distinguished: fimbria, infundibulum, ampulla, isthmus, and utero-tubal junction. Each region had particular histological characteristics that permit its identification. Fimbria and infundibulum had more ciliated cells, the ampulla had a similar proportion of secretory and ciliated cells, and isthmus and utero-tubal junction had more secretory cells. Crypts were observed in all oviductal regions, mainly in isthmus and utero-tubal junction. Fimbria presented packages of smooth musculature. Infundibulum and ampulla showed a thin smooth muscle layer (circular orientation of fibers). Isthmus and utero-tubal junction had a thick smooth muscle layer (inner longitudinal and outer circular orientation of fibers). A single and precise regionalization of oviduct could be very useful to compare studies that analyze the influence of natural conditions or treatments for tissue components or regions.