[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/) › Myometrium [Reproductive system](https://durgical.com/en/anatomy/system/reproductive-system/) · [Pelvis · Female](https://durgical.com/en/anatomy/region/pelvis/) # Myometrium The myometrium is the thick muscle wall of the uterus; it contracts in labour to push the baby out and then clamps the vessels to stop bleeding. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=pelvis&variant=female&select=myometrium&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The thick smooth-muscle wall of the uterus. ## What it does Contracts in labour and clamps the vessels after birth to stop bleeding. ## Key points - Risk factors for atony: an overdistended uterus (twins, excess amniotic fluid, a large baby), long or very fast labour, infection, fibroids and a retained placenta - Fibroids are named by position: submucous (bulging into the cavity; most linked with heavy bleeding and infertility), intramural, and subserous (sometimes on a stalk) - Adenomyosis: endometrial glands inside the myometrium make the uterus diffusely enlarged, globular and tender - In pregnancy the uterus grows mainly by enlargement (hypertrophy) of its muscle cells, and its oxytocin receptors increase toward term ## Key facts **Where** Thick smooth-muscle wall of the uterus (inner longitudinal, middle interlacing vascular, outer longitudinal layers) **Blood supply** Arcuate and radial branches of the uterine artery **Nerve** Uterovaginal plexus (from [inferior hypogastric plexus](https://durgical.com/en/anatomy/inferior-hypogastric-plexus/)): sympathetic T10–L1, parasympathetic S2–S4 **Function** Contractions of labour (oxytocin); after birth the interlacing fibres clamp the vessels ('living ligatures') ## Relations **Superficial** Perimetrium (serosa) over the body and fundus; at the sides the [broad ligament](https://durgical.com/en/anatomy/broad-ligament-of-uterus/), from which the [uterine artery](https://durgical.com/en/anatomy/uterine-artery/) sends arcuate branches into the vascular middle layer **Deep** [Endometrium](https://durgical.com/en/anatomy/endometrium/), with no submucosa between them ## Examination - Bimanual examination: a fibroid uterus is enlarged, firm and irregular; a uterus with adenomyosis is evenly enlarged, softer and tender - Fundal palpation after birth: a firm, contracted uterus at or below the umbilicus is normal; a soft, boggy, high uterus means atony ## On imaging Ultrasound shows fibroids as well-defined, usually hypoechoic masses that cast shadows. T2-weighted MRI maps their number and position before surgery (well-defined and dark) and shows adenomyosis as a thickened junctional zone (often quoted as over 12 mm). ## Common problems - Fibroids (leiomyomas) grow from it. - Poor contraction after birth (uterine atony) is the main cause of heavy bleeding after delivery. ## 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 - Atony is managed in steps: fundal massage and bimanual compression with uterotonic drugs, then compression sutures, uterine or [internal iliac artery](https://durgical.com/en/anatomy/internal-iliac-artery/) ligation or embolisation, and hysterectomy as the last resort - Myomectomy removes fibroids and keeps the uterus; a deep myometrial scar can rupture in a later labour - Uterine artery embolisation shrinks symptomatic fibroids by cutting off their blood supply - Red degeneration: a fibroid outgrows its blood supply in pregnancy, causing acute localised pain ## Memory aid Causes of postpartum haemorrhage, the 4 Ts: Tone (atony, the commonest), Trauma, Tissue (retained placenta) and Thrombin (clotting problems). ## Related conditions - [Postpartum haemorrhage](https://durgical.com/en/conditions/postpartum-haemorrhage/) - [Placental abruption](https://durgical.com/en/conditions/placental-abruption/) - [Uterine fibroids (leiomyomas)](https://durgical.com/en/conditions/uterine-fibroids/) - [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/) - [Preterm labour and birth](https://durgical.com/en/conditions/preterm-labour-and-birth/) - [Puerperal infection (postpartum endometritis and maternal sepsis)](https://durgical.com/en/conditions/puerperal-infection/) - [Placenta accreta spectrum](https://durgical.com/en/conditions/placenta-accreta-spectrum/) - [Uterine rupture](https://durgical.com/en/conditions/uterine-rupture/) - [Gestational trophoblastic neoplasia (choriocarcinoma)](https://durgical.com/en/conditions/gestational-trophoblastic-neoplasia/) ## Test yourself Think of the answer, then tap the question to see it. ## What is the commonest cause of postpartum haemorrhage, and how does the myometrium normally prevent it? Uterine atony (Tone, first of the 4 Ts); normally the contracting myometrium clamps the vessels after birth. ## Which factors increase the risk of myometrial atony after birth? An overdistended uterus (twins, excess fluid, large baby), long or very fast labour, infection, fibroids and a retained placenta. ## Which fibroids, by position, are most linked with heavy bleeding and infertility? Submucous fibroids, which bulge into the uterine cavity. ## How does a uterus with adenomyosis differ from a fibroid uterus on bimanual examination? Adenomyosis: evenly enlarged, softer and tender (globular). Fibroids: enlarged, firm and irregular. ## What is red degeneration of a fibroid? In pregnancy a fibroid outgrows its blood supply, causing acute localised pain. [Add to my cards (5)](https://durgical.app/estudiar/?add=/en/anatomy/myometrium/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** myometrium TA2 3520 **Official Spanish (DeCS)** Miometrio DeCS D009215 **English (TA2)** Myometrium **Also called** muscular coat 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=9407); [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/myometrium/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/myometrium/