A fluid-filled cavity called antrum is present in:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Tertiary follicle
An ovarian follicle grows in stages: primary, secondary, tertiary and then the mature Graafian follicle. The antrum appears at the tertiary stage.
(1) Primary follicle — Incorrect. The oocyte is surrounded by a single layer of granulosa cells. There is no cavity.
(2) Secondary follicle — Incorrect. It has more layers of granulosa cells and a new theca layer, but still no fluid-filled cavity.
(3) Tertiary follicle — Correct. It is the stage with a fluid-filled cavity, the antrum. Its theca is organised into an inner theca interna and an outer theca externa.
(4) Ruptured follicle — Incorrect. At ovulation the Graafian follicle ruptures and releases the ovum. The remains become the corpus luteum.
NCERT Extract:
Gametogenesis – …
