To better understand premenstrual syndrome, 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.

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 of the female reproductive tract includes:

• The uterus, cervix, and vaginal canal
• The fallopian tubes: these paired structures connect each ovary to the uterus.
• The ovaries: one on each side of the uterus. The normal ovary is approximately the size of an unshelled almond.