(menses) The monthly flow of blood from the female genital tract.

Menstruation, or period, is normal vaginal bleeding that occurs as part of a woman's monthly cycle. Every month, your body prepares for pregnancy. If no pregnancy occurs, the uterus, or womb, sheds its lining. The menstrual blood is partly blood and partly tissue from inside the uterus. It passes out of the body through the vagina. Periods usually start between age 11 and 14 and continue until menopause at about age 51. They usually last from three to five days. Besides bleeding from the vagina, you may have: Abdominal or pelvic cramping pain; Lower back pain; Bloating and sore breasts; Food cravings; Mood swings and irritability; Headache and fatigue. Premenstrual syndrome, or PMS, is a group of symptoms that start before the period. It can include emotional and physical symptoms. Consult your health care provider if you have big changes in your cycle. They may be signs of other problems that should be treated. NIH: National Institute of Child Health and Human Development

Periodic discharge of blood and tissue from the uterus. From puberty until menopause, menstruation occurs about every 28 days when a woman is not pregnant.

The cyclic, physiologic discharge through the vagina of blood and endometrial tissues from the nonpregnant uterus.

The normal physiologic discharge through the vagina of blood and mucosal tissues from the nonpregnant uterus.

The periodic shedding of the ENDOMETRIUM and associated menstrual bleeding in the MENSTRUAL CYCLE of humans and primates. Menstruation is due to the decline in circulating PROGESTERONE, and occurs at the late LUTEAL PHASE when LUTEOLYSIS of the CORPUS LUTEUM takes place.

Menstruation, periodic discharge from the vagina of blood, secretions, and disintegrating mucous membrane that had lined the uterus. The biological significance of the process in humans can best be explained by reference to the reproductive function in other mammals. In a number of species of wild...