DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Developing Graafian follicles. Light micrograph of a sectioned human ovary, showing two developing Graafian follicles. A Graafian follicle is a structure in the ovaries from which an ovum (egg cell) is released. It comprises an ovum (inner circle), surrounded by the zona granulosa (purple dots). The pale area in each follicle is the fluid-containing antrum. The cells in zona granulosa secrete follicle stimulating hormone (FSH) and produce oestrogen. FSH stimulates the maturation of the follicle. When mature it releases the ovum, which travels from the ovary down the Fallopian tube to the uterus. Normally, only one ovum is released each month, although several follicles develop each cycle.
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