Antral follicle

An antral follicle, is a tertiary follicle, a developing ovarian follicle that may progress to a mature pre-ovulatory follicle known as a Graafian follicle.

Definitions differ in where the shift into an antral follicle occurs in the staging of folliculogenesis, with some stating that it occurs when entering the secondary stage, and others stating that it occurs when entering the tertiary stage.

During folliculogenesis a cavity known as an antrum is formed. Follicular fluid begins to fill the antrum and when filled the follicle is known as an antral follicle.