The myometrium: birth, fists and fibroids
What is it? The middle of the three layers that form the wall of the uterus (womb). The myometrium makes up the bulk of the uterus and is made of densely packed, powerful muscle — powerful enough to help push a baby out. Where does the name come from? From the Greek words mys , meaning muscle, and metra , which means uterus. In what way does it undergo an amazing transformation? During pregnancy the uterus has to increase enormously in size and then, just as amazingly, return to its original state very soon after the birth. This is largely thanks to the remarkably adaptable myometrium. Before pregnancy, the uterus is fist-shaped and almost solid, with a tiny cavity of just 10ml. By the time the baby is due, the uterus has transformed into a thin-walled balloon with a capacity that is now more than 500 times greater; and yet it is still capable of strong, painful contractions. How does it manage to change so much? Rather than enlarging by producing new muscle cells, the myometrium expands during pregnancy because its cells actually stretch, growing longer and longer, until they are about half a millimetre long at the time of the birth. Why may women have their myometrium removed? Fibroids grow from cells in the myometrium. These very common, benign growths often don’t cause symptoms and don’t need treatment. If treatment is needed, one method is to remove them, either by taking out the whole uterus (hysterectomy) or just the fibroid (myomectomy), leaving the uterus intact.