A scanning electron microscopic study of the peritoneal mesothelium covering the genital tract and its ligaments in the cow

This study was undertaken to describe the surface features of the peritoneal mesothelium covering the genital tract and adjacent ligaments of the cow during the oestrous cycle. The relationship between mesothelial surface and spermatozoa was also evaluated after intra-uterine and intraperitoneal insemination. Surface features of mesothelial cells from 25 cyclic cows were examined by scanning electron microscopy and by image analysis. Presence of spermatozoa was evaluated by scanning electron microscopy in seven additional cows. In the external side of the infundibulum, the oviductal mucosa exceeds the free margin, forming a continuous band measuring 2.5-10 mm in width. This oviductal epithelium shows cyclical variations with a predominance of ciliated cells during the follicular phase. In respect of the mesothelium, no clear morphological differences were observed associated with the side of ovarian bursa (internal versus external), or with the phase of the oestrous cycle. Mesothelial cells covering the uterus and mesometrium have a higher microvilli density and length and a smaller cell surface area than in the oviduct and adjacent structures. The presence of solitary cilia in the mesosalpinx and mesotubarium superius (infundibulo-cornual ligament) of some specimens was also observed. When samples were processed without postfixation in osmium tetroxide, a layer of amorphous material covered all surfaces. After intra-uterine insemination of five cows, no spermatozoa were found on their peritoneal mesothelium. Numerous spermatozoa were found after intraperitoneal insemination being attached throughout mesothelial surfaces. These results indicate that there are morphological differences between regions, but no cyclic changes, in the surface features of mesothelial cells covering the genital tract and adjacent ligaments of the cow, and that spermatozoa can bind to mesothelial surfaces after intraperitoneal insemination.