STRUCTURE OF GERMINAL DISK REGION OF HENS OVARIAN FOLLICLE DURING RAPID GROWTH PHASE

Abstract

In a study on yolk transport mechanisms in Gallus domesticus, the germinal disc region of the ovarian follicle was examined by EM and compared with the non-disc region. The germinal disc is visible as a small white plaque at the surface of the yellow yolk mass of the oocyte in the final growth stage. Differences between the 2 regions were noted in the granulosa cell layer and in the surface layer of the oocyte. Above the disc the granulosa cells were more closely packed and less regularly arranged as a result of their mitotic activity. The oocyte surface layer was characterized by numerous microvilli and by coated vesicles, 70nm and 120nm diameter, which diminished in number with oocyte growth. By contrast, the surface of the bulk of the oocyte was indented with deep pouches and a layer of fuzzy material covered the external leaflet of the oolemma. Numerous coated pits and vesicles, 300nm diameter, were present in the cytoplasm. In the disc region, movement of plasma yolk precursors through the granulosa layer apparently was restricted and the inability of the germinal disc to incorporate yellow yolk precursors probably was related to differences in the oolemmal surface coat and the populations of coated vesicles.