Graafian follicle

The term Graaf follicle (vesicular follicle) refers to a mature ovarian follicle in the final stage of development following ovulation. Sometimes, however, this name refers purely to the preovulatory phase, a few hours before ovulation.

It is formed by an oocyte (about 130 μm in diameter) and surrounding supporting (follicular or granulose) cells. It has a spherical shape, in which there is an enlargement of the cavity (antra), which is filled with a fluid, between the follicular cells. The oocyte is located at the edge of this internal cavity, it is surrounded on all sides by an island of follicular cells - these cells therefore form the so-called cumulus oophorus. Surrounding the oocyte is an amorphous envelope, the 'zona pellucida.

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