Myometrial

Myometrial refers to anything related to the myometrium, the thick, muscular middle layer of the uterus. The myometrium lies between the endometrium, the inner lining, and the serosa or adventitia, and it is composed predominantly of smooth muscle cells arranged in interlacing bundles within a connective tissue matrix. It functions as the contractile tissue of the uterus and is essential for parturition and uterine tone.

During pregnancy the myometrium expands significantly, increasing in mass and size through smooth muscle hypertrophy and, to a lesser extent, hyperplasia. Hormonal influences, especially estrogen and progesterone, drive these changes. After delivery, the myometrium contracts to reduce uterine size and to constrict uterine blood vessels, helping to prevent hemorrhage; this process is known as involution. Labor contractions are coordinated by hormonal signals, including oxytocin and prostaglandins.

Clinical relevance of the myometrium includes conditions such as fibroids (leiomyomas), which are benign tumors arising from myometrial smooth muscle cells and can affect bleeding, fertility, and pregnancy. Adenomyosis is a condition in which endometrial tissue infiltrates the myometrium, often causing pain and heavier menses. Myometrial pathology can be evaluated with imaging techniques like ultrasound or MRI, and the term myometrial is used in descriptions of lesions, thickness, or changes confined to this muscular layer.