Light and electron microscopic study of the ovarian surface epithelium [OSE] of the adult albino rat

Twenty adult female albino rats were used in this study. They were divided into two groups. The first group included ten adult non-pregnant animals, while the second group included ten pregnant ones, that terminated at the middle of pregnancy [tenth day of gestation]. These animals were sacrificed after being anaesthetized. Then, the ovaries were extracted and prepared for light and electron microscopic examinations. The results revealed that the ovary of the non - pregnant group was covered with a single flat epithelial layer. The nuclei were found to lie in the larger portions of the cells that sent cytoplasmic attenuations, containing many vacuoles and covering the underlying tunica albuginea. This tunica was well-formed, containing many extra-cellular collagen fibrils .The fibroblasts were arranged into two or more layers, parallel to the surface epithelium. The cortical stroma showed many graafian follicles in different stages of development. The developing follicles were mostly bulging through the ovarian surface epithelium [OSE]. The ovary of the pregnant group showed OSE with some proliferative changes. These changes included proliferation of the cells of OSE and the underlying tunica albuginea, The OSE was formed of a single layer of flat epithelial cells but with more nuclei and nuclear irregularity and folding. Also, there was increased thickness of the tunica albuginea with increased vascularity and collagen fibrils,Examination of the cortical stroma showed general similarity between the pregnant and non-pregnant groups, regarding the presence of different stages of developing graafian follicles. However, these follicles were mostly not bulging through the OSE during pregnancy, despite the presence of mature graafian follicle. Also there were increased atretic follicles. This might be an indication of gradual disappearance of mature graafian follicles without rupture through OSE [without ovulation]. The changes occurring during pregnancy in OSE and underlying tunica albuginea might have a role in prevention of ovulation