Figure 5
From: Ultrastructural changes in oocytes during folliculogenesis in domestic mammals
Development of the zona pellucida (ZP) and cortical granules during follicular growth. A: Cat primary follicle with a completely formed ZP. B: Pig primary follicle without ZP. C: Bitch small secondary follicle in which patches of ZP material start to be deposited around the oocyte (arrows). D: Detail of a granulosa cell projection through the ZP into the oocyte where gap junctions (arrows) can be seen in a pig secondary follicle. E: Cow large secondary follicle with cortical granules organized in clusters. Observe the organelle-free zone around the oocyte nucleus. F: Cat secondary follicle with cortical granules (arrows) aligned close to the oocyte plasma membrane. Note the microvilli on the oocyte plasma membrane protruding into the ZP. O: oocyte, Nu: nucleus, GC: granulosa cells, ZP: zona pellucida, *: nucleolus, Mt: mitochondria, Mv: Microvilli.