Antralfollikel

Antralfollikel, or antral follicle, is a developmental stage of the ovarian follicle characterized by the formation of a fluid-filled cavity called the antrum. This cavity forms within the granulosa cell compartment as follicular fluid accumulates, creating a distinct antral chamber that separates the cumulus oophorus from the surrounding somatic layers.

Morphologically, an antral follicle contains an oocyte surrounded by cumulus cells, a stratified layer of granulosa cells, and thecal layers—the theca interna and theca externa. The growing antral follicle is supplied by follicular fluid that concentrates signaling molecules and hormones such as estrogens and inhibins.

Development and function: The antral phase arises from secondary follicles under gonadotropin influence, notably FSH, and progresses to a preovulatory Graafian (preovulatory) follicle. As the antrum enlarges, the follicle becomes more responsive to the LH surge that triggers ovulation and rupture, releasing the oocyte with its surrounding cumulus into the reproductive tract; the remaining follicular tissue forms the corpus luteum.

Clinical relevance: The number and size of antral follicles can be assessed as the antral follicle count (AFC), an indicator of ovarian reserve used in fertility evaluations and in assisted reproduction. Antral follicle dynamics reflect hormonal status and reproductive health.