BIOPHOTO ASSOCIATES / SCIENCE PHOTO LIBRARY BIOPHOTO ASSOCIATES / SCIENCE PHOTO LIBRARY
Graafian follicle. Light micrograph of a section through a Graafian follicle containing a nearly mature egg, in the cortex of a healthy ovary. At lower centre is the rounded full-grown secondary oocyte (egg). It must undergo meiotic division before it can be fertilised. The egg is surrounded by pink cells forming a corona radiata (CR). The CR is made of zona granulosa cells that stretch around the periphery of the follicle. A large grey follicular antrum is fluid-filled. At ovulation, the Graafian follicle ruptures and the mature egg (ovum) surrounded by CR leaves the ovary to pass into a fallopian tube for fertilisation. Stained with Azan. Magnification: x18 at 35mm size.
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