[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Histology](https://durgical.com/en/histology/) › [Reproductive system](https://durgical.com/en/histology/#a-reproductive) › Uterus and the endometrial cycle [Histology](https://durgical.com/en/histology/) · [Reproductive system](https://durgical.com/en/histology/#a-reproductive) # Uterus and the endometrial cycle - Organ The lining of the uterus grows, gets ready and is shed each month, following the hormones of the ovary. Updated 2026-11-01 **See it in 3D:** [Endometrium](https://durgical.com/en/anatomy/endometrium/) · [Body of uterus](https://durgical.com/en/anatomy/body-of-uterus/) · [Myometrium](https://durgical.com/en/anatomy/myometrium/) ## Key points - Functional layer: shed; basal layer: stays and regenerates; spiral arteries supply the functional layer and straight arteries the basal layer. - Proliferative phase: estradiol; straight tubular glands with mitoses. - Secretory phase: progesterone; glycogen vacuoles below the nucleus soon after ovulation, then tortuous saw-tooth glands and an edematous stroma. - Menstruation: progesterone falls, spiral arteries constrict, ischemia follows and the functional layer is shed. - Estrogen without progesterone causes endometrial hyperplasia and raises the risk of endometrioid carcinoma. ## What it is The uterine wall has three layers: endometrium (mucosa), myometrium (smooth muscle) and perimetrium (serosa). The endometrium has a functional layer, which changes and is lost at menstruation, and a basal layer, which stays and regenerates it. Estradiol makes the endometrium grow and progesterone makes it secretory and ready for implantation. Dating the endometrium by its glands and stroma is a classic histology question. ## Structure - Endometrium: simple columnar epithelium with ciliated and secretory cells, tubular glands and a very cellular stroma. - Myometrium: thick interlacing bundles of smooth muscle with vessels; it grows a lot in pregnancy by hypertrophy and hyperplasia. - In pregnancy the stroma becomes decidua: large, polygonal, pale cells. ## Function - Prepare a bed for embryo implantation each cycle. - Form the maternal part of the placenta (decidua basalis). - Expel the fetus at birth by contraction of the myometrium. ## Endometrial phases (reference 28-day cycle) | Phase | Hormone in charge | What you see | | --- | --- | --- | | Menstrual (days 1 to 4) | Fall in progesterone and estradiol | Collapsed stroma, blood and shedding of the functional layer | | Proliferative (days 5 to 14) | Estradiol from the follicle | Straight glands with mitoses; dense stroma; the endometrium thickens | | Early secretory (days 15 to 19) | Progesterone from the corpus luteum | Glycogen vacuoles below the nucleus of gland cells | | Late secretory (days 20 to 28) | Progesterone | Tortuous glands with secretion in the lumen, edematous stroma, predecidual change around spiral arteries | ## Clinical notes - Endometriosis: endometrial glands and stroma outside the uterus; pelvic pain and infertility. - Adenomyosis: endometrium inside the myometrium; a large, painful uterus. - Leiomyomas (fibroids): benign smooth muscle tumours, the most common tumours of the uterus. - Postmenopausal bleeding: the endometrium must be studied because of the risk of carcinoma. ## Memory aid Estradiol builds the house and progesterone furnishes it; if nobody moves in, the spiral-artery scaffolding collapses and the functional layer goes. ## Test yourself Think of the answer, then tap the question to see it. ## Which endometrial layer is lost at menstruation, and which regenerates it? The functional layer is lost; the basal layer stays and regenerates it. ## Which finding marks the start of the secretory phase? Glycogen vacuoles below the nucleus of the gland cells, soon after ovulation. ## Which hormone drives the proliferative phase? Estradiol from the growing follicles. ## Why does estrogen unopposed by progesterone raise the risk of endometrial cancer? It drives continuous gland proliferation, which can lead to hyperplasia and then to endometrioid carcinoma. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/histology/uterus-and-the-endometrial-cycle/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Endometrium](https://durgical.com/en/anatomy/endometrium/) - [Body of uterus](https://durgical.com/en/anatomy/body-of-uterus/) - [Myometrium](https://durgical.com/en/anatomy/myometrium/) ## Related - [Ovary: follicles, ovulation and corpus luteum](https://durgical.com/en/histology/ovary-follicles-ovulation-and-corpus-luteum/) - [Cervix and vagina: the transformation zone](https://durgical.com/en/histology/cervix-and-vagina-the-transformation-zone/) - [Placenta](https://durgical.com/en/histology/placenta/) - [Smooth muscle](https://durgical.com/en/histology/smooth-muscle/) ## Related conditions - [Endometriosis](https://durgical.com/en/conditions/endometriosis/) - [Endometrial cancer](https://durgical.com/en/conditions/endometrial-cancer/) - [Uterine fibroids (leiomyomas)](https://durgical.com/en/conditions/uterine-fibroids/) - [Adenomyosis](https://durgical.com/en/conditions/adenomyosis/) [← 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); [Genital Tract](https://training.seer.cancer.gov/anatomy/reproductive/female/tract.html) (National Cancer Institute, SEER Training Modules, 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/histology/uterus-and-the-endometrial-cycle/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/histology/uterus-and-the-endometrial-cycle/