To better understand painful menstrual periods, it helps to understand the anatomy of the uterus, cervix, and Fallopian tubes.

The female reproductive organs include the vagina, cervix, uterus, fallopian tubes and ovaries. The lining of the uterus is called the endometrium.

Before ovulation, the endometrium grows and becomes thick: the endometrial tissue and blood vessels support a fertilized egg when it enters the uterus.

If an egg is not fertilized, it does not attach to the endometrium and the endometrium breaks down. The uterus sheds the endometrium, which causes the bleeding associated with the menstrual period.

The uterus is composed of smooth muscle. During the normal menstrual cycle the uterus will undergo successive periods of contraction followed by relaxation. At times the contractions are more pronounced, and can cause discomfort.

Anatomy examples:

• The uterus, cervix, and vaginal canal
• The bladder
• The fallopian tubes:
• These paired structures connect each ovary to the uterus
• The ovaries:
• One on each side of the uterus. A normal adult ovary is about the size of an unshelled almond
• Female organs during a pelvic examination