[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Pelvis · Female](https://durgical.com/en/anatomy/region/pelvis/) › Endometrium [Reproductive system](https://durgical.com/en/anatomy/system/reproductive-system/) · [Pelvis · Female](https://durgical.com/en/anatomy/region/pelvis/) # Endometrium The endometrium is the inner lining of the uterus; it thickens each menstrual cycle and is shed as the period if no pregnancy implants. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=pelvis&variant=female&select=endometrium&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The inner lining of the uterus. ## What it does Thickens each cycle under oestrogen and progesterone and is shed as the period if no pregnancy implants. ## Key points - The basal layer survives each period and regrows the functional layer; damage to it (vigorous curettage, infection) causes intrauterine adhesions (Asherman syndrome) - As progesterone falls at the end of the cycle the spiral arteries constrict, the functional layer becomes ischaemic and is shed - Unopposed oestrogen (obesity, anovulation as in polycystic [ovary](https://durgical.com/en/anatomy/ovary/) syndrome, oestrogen-only therapy) drives hyperplasia and endometrioid cancer - In postmenopausal bleeding a thin endometrium on transvaginal ultrasound (about 4 mm or less in many guidelines) makes cancer unlikely; a thicker one leads to sampling ## Key facts **Where** Mucosa lining the uterine cavity: functional layer (shed) over a basal layer **Blood supply** Radial then spiral arteries (functional layer) and straight arteries (basal layer), from the [uterine artery](https://durgical.com/en/anatomy/uterine-artery/) **Nerve** Uterovaginal plexus (from [inferior hypogastric plexus](https://durgical.com/en/anatomy/inferior-hypogastric-plexus/)): sympathetic T10–L1, parasympathetic S2–S4 **Function** Proliferates (oestrogen) and becomes secretory (progesterone) each cycle; shed at menstruation; site of implantation ## Relations **Deep** [Myometrium](https://durgical.com/en/anatomy/myometrium/), with no submucosa between them; the irregular border is part of the junctional zone **Superficial** The uterine cavity; continuous with the lining of the [uterine tubes](https://durgical.com/en/anatomy/uterine-tube/) at the tubal openings and with the endocervical canal at the internal os ## How to find it Not palpable. Seen directly at hysteroscopy, where its colour, thickness, polyps and focal lesions guide a targeted biopsy, and sampled blindly with a thin suction cannula passed through the [cervix](https://durgical.com/en/anatomy/cervix-of-uterus/). ## On imaging Transvaginal ultrasound measures the double-layer thickness in the sagittal plane: a thin bright line after menstruation, a triple-line pattern in the proliferative phase and a thick, evenly bright lining in the secretory phase. Saline infusion sonohysterography outlines polyps and submucous fibroids. ## Common problems - Endometriosis: tissue like it grows outside the uterus. - Polyps and thickening; endometrial cancer (warning sign: bleeding after menopause). ## How it is diagnosed Pelvic examination and ultrasound (often transvaginal); hysteroscopy or a sample of the lining (biopsy) when needed; MRI for some cases. ## Treatment - Medicines or a hormonal intrauterine device for heavy bleeding. - Removal of fibroids (myomectomy) or blocking their blood supply (embolisation). - Hysterectomy (removal of the uterus) when other treatments are not enough or for cancer. - Caesarean section to deliver a baby through the [abdomen](https://durgical.com/en/anatomy/region/abdomen/). ## Clinical notes - Sampled by office aspiration biopsy, dilatation and curettage or hysteroscopy; its histology changes predictably through the proliferative and secretory phases - Asherman syndrome: scant or absent periods and infertility from adhesions after damage to the basal layer - Endometriosis: endometrial-type tissue outside the uterus, most often on the ovaries, the [uterosacral ligament](https://durgical.com/en/anatomy/uterosacral-ligament/) and the [rectouterine pouch](https://durgical.com/en/anatomy/rectouterine-pouch/); retrograde menstruation through the tubes is the leading theory - In pregnancy it becomes the decidua; where the decidua is thin or missing (over a scar) the placenta can invade too deeply (placenta accreta spectrum) ## Related conditions - [Lynch syndrome (hereditary non-polyposis colorectal cancer)](https://durgical.com/en/conditions/lynch-syndrome/) - [Miscarriage (early pregnancy loss)](https://durgical.com/en/conditions/miscarriage/) - [Uterine fibroids (leiomyomas)](https://durgical.com/en/conditions/uterine-fibroids/) - [Endometriosis](https://durgical.com/en/conditions/endometriosis/) - [Polycystic ovary syndrome](https://durgical.com/en/conditions/polycystic-ovary-syndrome/) - [Pelvic inflammatory disease](https://durgical.com/en/conditions/pelvic-inflammatory-disease/) - [Endometrial cancer](https://durgical.com/en/conditions/endometrial-cancer/) - [Adenomyosis](https://durgical.com/en/conditions/adenomyosis/) - [Abnormal uterine bleeding](https://durgical.com/en/conditions/abnormal-uterine-bleeding/) - [Dysmenorrhoea](https://durgical.com/en/conditions/dysmenorrhoea/) - [Molar pregnancy (hydatidiform mole)](https://durgical.com/en/conditions/molar-pregnancy/) - [Puerperal infection (postpartum endometritis and maternal sepsis)](https://durgical.com/en/conditions/puerperal-infection/) - [Septic and unsafe abortion](https://durgical.com/en/conditions/septic-and-unsafe-abortion/) - [Endometrial hyperplasia](https://durgical.com/en/conditions/endometrial-hyperplasia/) - [Menopause and climacteric syndrome](https://durgical.com/en/conditions/menopause-and-climacteric-syndrome/) - [Female infertility](https://durgical.com/en/conditions/female-infertility/) - [Gestational trophoblastic neoplasia (choriocarcinoma)](https://durgical.com/en/conditions/gestational-trophoblastic-neoplasia/) - [Asherman syndrome (intrauterine adhesions)](https://durgical.com/en/conditions/asherman-syndrome/) ## Test yourself Think of the answer, then tap the question to see it. ## Which layer of the endometrium survives each period, and what results if it is damaged? The basal layer, which regrows the functional layer; damage (vigorous curettage, infection) causes intrauterine adhesions: Asherman syndrome. ## What causes the functional layer of the endometrium to be shed at the end of the cycle? Falling progesterone makes the spiral arteries constrict; the functional layer becomes ischaemic and is shed. ## What drives endometrial hyperplasia and endometrioid cancer? Unopposed oestrogen: obesity, anovulation (as in polycystic ovary syndrome) or oestrogen-only therapy. ## In postmenopausal bleeding, what does a thin endometrium on transvaginal ultrasound suggest? Cancer is unlikely when it is about 4 mm or less in many guidelines; a thicker endometrium leads to sampling. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/endometrium/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** endometrium TA2 3521 **Official Spanish (DeCS)** Endometrio DeCS D004717 **English (TA2)** Endometrium **Also called** mucous membrane of uterus ## Related - [Body of uterus](https://durgical.com/en/anatomy/body-of-uterus/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=4796); [Anatomy, Abdomen and Pelvis: Uterus](https://www.ncbi.nlm.nih.gov/books/NBK470297/). ## **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/anatomy/endometrium/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/endometrium/