Which one of the following pairs of ovarian follicle and its feature…

The correct answer is Option (3) → Graafian follicle – Ruptures to release the secondary oocyte (ovum) from the ovary

An ovarian follicle is a primary oocyte together with the cells that surround it. It grows through a fixed series of stages: primary follicle → secondary follicle → tertiary follicle → Graafian follicle. Each stage has its own mark, so a pair is correct only when the feature belongs to that stage.

Option (1) Primary follicle – Primary oocyte surrounded by more layers of granulosa cells and a new theca — Incorrect. More layers of granulosa cells and a new theca mark the secondary follicle. A primary follicle has a primary oocyte with a single layer of granulosa cells and no theca.

Option (2) Secondary follicle – Fluid-filled cavity called antrum — Incorrect. The antrum first appears in the tertiary follicle. The secondary follicle has gained granulosa layers and a theca, but it has no fluid-filled cavity yet.

Option (3) Graafian follicle – Ruptures to release the secondary oocyte (ovum) from the ovary — Correct. The Graafian follicle is the mature follicle formed from the tertiary follicle. The secondary oocyte inside it is covered by the zona pellucida. In the middle of the menstrual cycle, the LH surge makes this follicle rupture and release the ovum; this is ovulation.

Option (4) Tertiary follicle – Primary oocyte surrounded by a layer of granulosa cells — Incorrect. A single layer of granulosa cells round the primary oocyte is the primary follicle. A tertiary follicle has a fluid-filled antrum, and its theca is organised into theca interna and theca externa.

NCERT Extract:
Gametogenesis – “… Each primary oocyte then gets surrounded by a layer of granulosa cells and is called the primary follicle (Figure 2.7). A large number of these follicles degenerate during the phase from birth to puberty. Therefore, at puberty only 60,000-80,000 primary follicles are left in each ovary. The primary follicles get surrounded by more layers of granulosa cells and a new theca and are called secondary follicles. The secondary follicle soon transforms into a tertiary follicle which is characterised by a fluid filled cavity called antrum.”
Gametogenesis – “… The tertiary follicle further changes into the mature follicle or Graafian follicle (Figure 2.7). The secondary oocyte forms a new membrane called zona pellucida surrounding it. The Graafian follicle now ruptures to release the secondary oocyte (ovum) from the ovary by the process called ovulation.”

Figure 2.7 Diagrammatic Section view of ovary