An ovarian follicle is an oocyte together with the surrounding supporting cells in an ovary. Follicle development changes both the oocyte's environment and the organization of the surrounding tissue. Growing follicles acquire granulosa and theca cell layers; later stages can develop a fluid-filled cavity.[ref]
Anatomy and Physiology 2e by J. Gordon Betts and others. Section 27.2, ovarian follicles and follicular development
A follicle is thus more than an egg under another name. Its supporting cells participate in signaling and steroid production, while interactions with the oocyte support development. Following ovulation, remaining follicular tissue can become the corpus luteum. The oocyte's fate and the supporting tissue's fate therefore diverge during the same reproductive event.
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