The uterus has 3 layers:
- Endometrium. This is the inner lining.
- Myometrium. This is the thick middle muscle layer of the corpus. This expands during pregnancy to hold the growing fetus.
- Serosa. This is the outer smooth layer. It covers the uterus.
In women who still have their periods, one ovary releases an egg into a fallopian tube each month. During this time, the endometrium becomes thicker to prepare for a fertilized egg. If the egg isn’t fertilized, it leaves the uterus through the vagina. Your endometrial lining is shed as your menstrual period. If the egg joins with a male sperm cell, this fertilized egg attaches to the endometrium. The uterus protects the growing fetus during pregnancy. During labor, the muscles of the myometrium help push the baby out through the cervix. The smooth serosa makes it easy for the uterus to move in the pelvis as needed.
The female hormones estrogen and progesterone maintain this healthy process. Your ovaries make most of these hormones.