Menstruation

Figure showing the progression of the menstrual cycle and the different hormones contributing to it

Menstruation, often referred to as a period or monthly, is the physiological process whereby the uterus sheds its inner lining, known as the endometrium, resulting in the discharge of blood and mucus through the vagina. This process is a central part of the female reproductive cycle and is regulated by fluctuating levels of hormones.

Onset of Menstruation

Menstruation usually begins between the ages of twelve and fifteen, an event known as menarche. In certain cases, menstruation may start as early as eight years of age and still be considered within normal limits. The average age of menarche tends to be later in developing countries and earlier in developed ones.

Menstrual Cycle

The menstrual cycle typically lasts 21 to 45 days in adolescents and 21 to 31 days in adults, with an average of 28 days. Menstrual bleeding or 'menses' usually lasts between 2 to 7 days. Menstruation ceases during pregnancy and may not resume during initial months of breastfeeding. Menstruation also ceases permanently after menopause, which usually occurs between the ages of 45 and 55.

Symptoms Associated with Menstruation

Up to 80% of women report experiencing symptoms prior to menstruation. These symptoms may include acne, breast tenderness, bloating, fatigue, irritability, and mood changes. When these symptoms interfere with daily life, they may be classified as premenstrual syndrome (PMS). Severe PMS symptoms occur in approximately 3 to 8% of women.

Irregularities and Disorders

Irregularities in the menstrual cycle, such as the absence of menstruation (amenorrhea) or painful menstruation (dysmenorrhea), can often be a sign of underlying health issues. Amenorrhea is defined as the absence of menstruation by age 15, or a lapse of 90 days without a period. Abnormal bleeding, such as intermenstrual bleeding or heavy menstrual bleeding, can also occur.

Menstruation in Other Animals

Menstruation is not exclusive to humans and also occurs in other primates, including apes and monkeys.

Hormonal Regulation

The menstrual cycle is regulated by a complex interplay of hormones, particularly estrogen and progesterone, which lead to the growth and shedding of the uterine lining. If an egg, released from the ovary around the 14th day of the cycle, is not fertilized, the thickened uterine lining is shed during menstruation. If fertilization occurs, the uterine lining serves to nourish the developing embryo.

External links

• Museum of Menstruation

See Also

• Menarche
• Menopause
• Premenstrual syndrome
• Amenorrhea
• Dysmenorrhea

References

Menstruation Resources
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