Light micrograph of a mature, ovarian (Graafian) follicle. The large pale pink body is a fluid- filled cavity known as the follicular antrum. In the follicle lies a single egg, the oocyte, which is surrounded by a layer of cells, the corona radiata. This is attached to the follicular wall by thin bridges of cells, which break down just before ovulation. At ovulation, the mature follicle ruptures and the ovum is released into the peritoneal cavity, where it is received into the fallopian tube for possible fertilisation. Below the large ripe follicle is a smaller follicle at an earlier stage of development. Magnification: x20 at 6x4.5cm size