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[Histology](https://durgical.com/en/histology/) · [Reproductive system](https://durgical.com/en/histology/#a-reproductive)

# Ovary: follicles, ovulation and corpus luteum

- Organ

The ovary keeps immature eggs in follicles; each cycle one matures, is released and leaves a corpus luteum that makes progesterone.

Updated 2026-11-01

**See it in 3D:** [Ovaries](https://durgical.com/en/anatomy/ovary/)

## Key points

- The primary oocyte is arrested in prophase of meiosis I from fetal life until shortly before ovulation.
- Before ovulation it finishes meiosis I and a secondary oocyte arrested in metaphase II is released; it completes meiosis only if fertilised.
- Two-cell model: the theca interna makes androgens under LH and the granulosa turns them into estradiol with aromatase, under FSH.
- The LH surge triggers ovulation; the corpus luteum makes progesterone and, without pregnancy, regresses to a corpus albicans.
- Most follicles never ovulate: they undergo atresia.

## What it is

The ovary has a cortex with follicles at different stages and a medulla with vessels. Each follicle is an oocyte surrounded by granulosa cells and, as it grows, by theca. Every month the gonadotropins recruit follicles; one becomes dominant, ovulates and its wall turns into the corpus luteum. The follicle stages and their hormones are the basis of the menstrual cycle and of diseases such as polycystic ovary syndrome.

## Structure

- Surface: simple cuboidal epithelium (misnamed germinal) over a dense tunica albuginea.
- Cortex: primordial follicles at the periphery and growing follicles deeper, in a very cellular stroma.
- Corpus luteum: a folded mass of granulosa lutein cells (large, pale) and theca lutein cells (small, at the edges).

## Function

- Make mature oocytes, usually one per cycle.
- Make estradiol in the follicular phase and progesterone in the luteal phase.
- Support early pregnancy through the corpus luteum, kept alive by hCG, until the placenta takes over hormone production.

## Follicle stages

| Stage | What it looks like | Key point |
| --- | --- | --- |
| Primordial | Primary oocyte with one layer of flat cells | Ovarian reserve; the most numerous |
| Primary | Cuboidal granulosa, first one layer then several; the zona pellucida appears | Growth begins |
| Secondary (antral) | Fluid spaces that form an antrum; theca interna and externa | Theca makes androgens and granulosa makes estradiol |
| [Mature (Graafian)](https://durgical.com/en/conditions/ovarian-cyst/) | Large antrum; oocyte on the cumulus oophorus, ringed by the corona radiata | Ovulates with the LH surge; if it fails to ovulate it may persist as a follicular cyst |
| Corpus luteum | Large, pale, lipid-rich lutein cells in a folded wall | Progesterone; kept alive by hCG in pregnancy |
| Corpus albicans | White hyaline scar | End of the corpus luteum without pregnancy |

## Clinical notes

- Polycystic ovary syndrome: many small antral follicles at the periphery, hyperplastic theca and androgen excess, with anovulation.
- Functional cysts (follicular or corpus luteum): common and almost always benign; they can rupture or twist the ovary.
- Most ovarian cancers are surface epithelial; high-grade serous carcinoma is the deadliest.

## Memory aid

The follicle grows like a house: first a bare room (primordial), then brick walls (primary), then a pool (antrum), and at the end the empty house becomes a progesterone factory.

## Test yourself

Think of the answer, then tap the question to see it.

## In which phase of meiosis is the oocyte of a primordial follicle arrested?

In prophase of meiosis I (diplotene), from fetal life until shortly before ovulation.

## Which follicle cell makes androgens and which turns them into estradiol?

The theca interna makes androgens under LH; the granulosa aromatises them to estradiol under FSH.

## What does the follicle become after ovulation, and what does it secrete?

The corpus luteum, which secretes mainly progesterone and some estradiol.

## What keeps the corpus luteum alive in early pregnancy?

The hCG made by the trophoblast.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/histology/ovary-follicles-ovulation-and-corpus-luteum/)

## See it in 3D

The structures of Durgical's 3D anatomy where it is found.

- [Ovaries](https://durgical.com/en/anatomy/ovary/)

## Related

- [Uterus and the endometrial cycle](https://durgical.com/en/histology/uterus-and-the-endometrial-cycle/)
- [Uterine tube](https://durgical.com/en/histology/uterine-tube/)
- [Cell cycle, mitosis and meiosis](https://durgical.com/en/histology/cell-cycle-mitosis-and-meiosis/)
- [Pituitary: adenohypophysis and neurohypophysis](https://durgical.com/en/histology/pituitary-adenohypophysis-and-neurohypophysis/)

## Related conditions

- [Polycystic ovary syndrome](https://durgical.com/en/conditions/polycystic-ovary-syndrome/)
- [Ovarian cyst](https://durgical.com/en/conditions/ovarian-cyst/)
- [Ovarian cancer](https://durgical.com/en/conditions/ovarian-cancer/)

[← All of histology](https://durgical.com/en/histology/)

Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.

Sources: [27.2 Anatomy and Physiology of the Ovarian Reproductive System](https://openstax.org/books/anatomy-and-physiology-2e/pages/27-2-anatomy-and-physiology-of-the-ovarian-reproductive-system) (OpenStax, Rice University, 2022); [Ovaries](https://training.seer.cancer.gov/anatomy/reproductive/female/ovaries.html) (National Cancer Institute, SEER Training Modules, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/histology/ovary-follicles-ovulation-and-corpus-luteum/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/histology/ovary-follicles-ovulation-and-corpus-luteum/