follicular antrum

antral cavity

Region of ovarian follicle filled with follicular fluid.

Type Organ
Parent Structure anatomical space
Latin Name antral cavity
FMA ID 18675

Frequently Asked Questions

When does the follicular antrum form?
The follicular antrum begins to form during the transition from secondary to tertiary follicle, typically in the late preantral stage. Accumulating follicular fluid secreted by granulosa cells coalesces into a single fluid-filled cavity. This process, called antrum formation or cavitation, marks a major turning point in folliculogenesis and is estrogen-dependent.
What is the structural significance of the follicular antrum?
The antrum divides the granulosa cells into two functional populations: the mural granulosa cells lining the follicle wall, and the cumulus granulosa cells surrounding the oocyte. This spatial organization determines how hormonal signals are processed and how the oocyte communicates with supporting cells through gap junctions.
How does the follicular antrum change during follicle maturation?
As the follicle matures from early antral to the preovulatory (Graafian) stage, the antrum expands dramatically — from microscopic to over 15 mm. This expansion is driven by continued fluid secretion and is reflected in ultrasound measurements used to monitor follicle development during fertility treatments.

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Educational Disclaimer

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Data sources: Terminologia Anatomica, Foundational Model of Anatomy, Wikidata.