Section of ovary: follicles to corpus luteumअंडाशय की काट: पुटिका से पीत पिंड तक

NCERT Fig 2.7 · Class 12 Biology · Chapter 2 · interactive diagram

Parts and their functions

• Primary follicle (प्राथमिक पुटक) — A primary oocyte surrounded by a layer of granulosa cells. Many follicles degenerate from birth to puberty — only 60,000–80,000 remain in each ovary at puberty.
• Secondary follicle (द्वितीयक पुटक) — Primary follicle gets more layers of granulosa cells and a new theca.
• Tertiary follicle (तृतीयक पुटक) — Has a fluid-filled cavity, the ANTRUM; theca organises into theca interna and theca externa. The primary oocyte now completes meiosis I.
• Graafian follicle (ग्राफी पुटक) — The mature follicle. It holds the secondary oocyte, which has formed a new membrane, the zona pellucida.
• Ovulation (अंडोत्सर्ग) — The Graafian follicle ruptures and releases the secondary oocyte (ovum). Triggered by the LH surge, around day 14.
• Corpus luteum (पीत पिंड) — Remains of the Graafian follicle after ovulation; secretes large amounts of PROGESTERONE, which maintains the endometrium.
• Cortex (वल्कुट) — Peripheral zone of the ovarian stroma, where follicles develop.
• Medulla (मध्यांश) — Inner zone of the stroma.
• Blood vessels (रक्त वाहिकाएँ) — Supply the ovary.

Steps

1. Primary follicle: primary oocyte + a layer of granulosa cells.
2. Secondary follicle: more granulosa layers + theca.
3. Tertiary follicle: fluid-filled antrum; theca interna & externa.
4. Graafian follicle: secondary oocyte with zona pellucida.
5. Ovulation: the follicle ruptures and releases the ovum (secondary oocyte).
6. Corpus luteum forms from the ruptured follicle and secretes progesterone.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 2.7. Report a mistake