[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [General embryology: weeks 1 to 8](https://durgical.com/en/embryology/#a-general) › Ovarian cycle, ovulation and the corpus luteum [Embryology](https://durgical.com/en/embryology/) · [General embryology: weeks 1 to 8](https://durgical.com/en/embryology/#a-general) # Ovarian cycle, ovulation and the corpus luteum - Process Each month a follicle matures, releases an egg and leaves a corpus luteum that prepares the uterus for a possible pregnancy. Updated 2026-11-01 **See it in 3D:** [Ovaries](https://durgical.com/en/anatomy/ovary/) · [Uterine tubes](https://durgical.com/en/anatomy/uterine-tube/) · [Infundibulum and fimbriae](https://durgical.com/en/anatomy/infundibulum-of-uterine-tube/) · [Endometrium](https://durgical.com/en/anatomy/endometrium/) ## Key points - The LH surge triggers ovulation and the resumption of meiosis I. - The luteal phase lasts about 14 days; cycle variation lies in the follicular phase. - Corpus luteum = progesterone; hCG maintains it in early pregnancy. - Two-cell theory: theca (LH, androgens) and granulosa (FSH, aromatase, estradiol). ## What it is The ovarian cycle is driven by hypothalamic GnRH and pituitary FSH and LH. In the follicular phase several follicles grow and one becomes dominant; the LH surge triggers ovulation; in the luteal phase the corpus luteum makes progesterone that keeps the endometrium secretory. If pregnancy occurs, trophoblast hCG rescues the corpus luteum. ## Key facts - Follicular phase: its length varies with the cycle; FSH recruits follicles and one dominates. - Theca interna makes androgens; granulosa converts them to estradiol (aromatase). - LH surge: the oocyte finishes meiosis I and ovulation follows shortly (around day 14 of a 28-day cycle). - Luteal phase: fairly constant, about 14 days. - Without fertilization the corpus luteum degenerates in about 10 days into the corpus albicans; progesterone falls and menstruation follows. - In pregnancy, hCG keeps the corpus luteum going until the placenta makes enough progesterone, near the end of the first trimester. ## Step by step - Primordial follicle: a primary oocyte surrounded by flat cells. - Primary follicle: cuboidal granulosa cells and the zona pellucida appear. - Secondary (antral) follicle: a fluid-filled cavity plus theca interna and externa layers. - Mature (Graafian) follicle: the oocyte sits on the cumulus oophorus, ready to leave. - Ovulation: the follicle ruptures and the tubal fimbriae pick up the oocyte with its corona radiata. - Corpus luteum: granulosa and theca cells luteinize and secrete progesterone and estrogens. ## Markers - GnRH - FSH - LH - Estradiol - Progesterone ## Clinical notes - Polycystic ovary syndrome: chronic anovulation, hyperandrogenism and many small arrested follicles. - Mid-cycle pain (Mittelschmerz): one-sided pelvic discomfort at ovulation. - Corpus luteum cyst: can rupture and bleed, mimicking ectopic pregnancy. - Ovulation day is estimated by counting 14 days back from the next period, not forward. ## Memory aid Theca 'cooks' the androgens and granulosa 'frosts' them into estradiol; when LH gives the signal, the follicle opens the door. ## Test yourself Think of the answer, then tap the question to see it. ## Which hormone triggers ovulation? The LH surge, which also makes the oocyte finish meiosis I. ## Which phase of the ovarian cycle has a nearly constant length? The luteal phase, about 14 days. Differences in cycle length lie in the follicular phase. ## What keeps the corpus luteum alive early in pregnancy? hCG from the syncytiotrophoblast, acting on the corpus luteum's LH receptor. ## Which follicle cell converts androgens to estradiol? The granulosa cell, through FSH-stimulated aromatase. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/embryology/ovarian-cycle-ovulation-and-the-corpus-luteum/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Ovaries](https://durgical.com/en/anatomy/ovary/) - [Uterine tubes](https://durgical.com/en/anatomy/uterine-tube/) - [Infundibulum and fimbriae](https://durgical.com/en/anatomy/infundibulum-of-uterine-tube/) - [Endometrium](https://durgical.com/en/anatomy/endometrium/) ## Related - [Gametogenesis: spermatogenesis and oogenesis](https://durgical.com/en/embryology/gametogenesis-spermatogenesis-and-oogenesis/) - [Fertilization: capacitation, acrosome reaction and zona reaction](https://durgical.com/en/embryology/fertilization-capacitation-acrosome-reaction-and-zona-reaction/) - [Week 1: cleavage, morula, blastocyst and implantation](https://durgical.com/en/embryology/week-1-cleavage-morula-blastocyst-and-implantation/) - [Trophoblast and hCG; gestational trophoblastic disease](https://durgical.com/en/embryology/trophoblast-and-hcg-gestational-trophoblastic-disease/) - [Gestational age vs fertilization age: how pregnancy is dated](https://durgical.com/en/embryology/gestational-age-vs-fertilization-age-how-pregnancy-is-dated/) ## Related conditions - [Polycystic ovary syndrome](https://durgical.com/en/conditions/polycystic-ovary-syndrome/) - [Ovarian cyst](https://durgical.com/en/conditions/ovarian-cyst/) - [Abnormal uterine bleeding](https://durgical.com/en/conditions/abnormal-uterine-bleeding/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: Langman's Medical Embryology, 13th ed., ch. 3: First Week of Development: Ovulation to Implantation (Wolters Kluwer, 2015); [Polyendocrine metabolic ovarian syndrome: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000369.htm) (MedlinePlus (U.S. National Library of Medicine), 2026); [Fetal development: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/002398.htm) (MedlinePlus (U.S. National Library of Medicine), 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/ovarian-cycle-ovulation-and-the-corpus-luteum/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/ovarian-cycle-ovulation-and-the-corpus-luteum/