endometru

The endometrium is the mucous membrane that lines the inside of the uterus. It consists of two layers: the functional layer, which thickens and sheds during each menstrual cycle, and the basalis layer, which remains to regenerate the lining. The tissue contains glandular epithelium, stroma, and a rich network of blood vessels, including spiral arteries that remodel across the cycle.

During the menstrual cycle, ovarian hormones drive changes: estrogen promotes proliferation and thickening in the proliferative (follicular) phase; after ovulation, progesterone induces secretory changes with glandular secretions and decidualization of the stroma, preparing the lining for possible embryo implantation. If fertilization does not occur, the functional layer is shed as menstrual blood, and the cycle begins again.

Embryologically, the endometrium develops from the Müllerian ducts. In pregnancy, the stroma undergoes decidualization and endometrial glands increase secretions to support implantation until placental function is established.

Clinical relevance includes assessment of endometrial thickness to evaluate abnormal uterine bleeding and infertility. Pathologies include endometrial hyperplasia and endometrial cancer, often linked to estrogen exposure, as well as endometritis and postmenopausal atrophy. Diagnostic approaches commonly involve transvaginal ultrasound to measure thickness and endometrial biopsy for histology.