- Related Topics:
- menstrual cycle
- dysmenorrhea
menstruation
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What is menstruation?
Menstruation, also known as a period or monthlies, refers to the periodic discharge of blood, secretions, and disintegrating mucous membrane from the vagina. This discharge comes from the shedding of the endometrium, the lining of the uterus, when pregnancy does not occur. The process recurs in a cycle, typically lasting about 28 days, and marks the beginning and end of each menstrual cycle. Menstruation usually lasts around five days, though duration and flow can vary. The menstrual cycle continues until menopause, marking the end of a woman's reproductive life.
8 Britannica Sources- ovary: Regulation of ovarian function
- menstruation
- menopause: Menopause and ovarian function
- Synonyms of menstruation
- human development: Development of the reproductive organs and secondary sex characteristics
- human reproductive system: The endometrium in the menstrual cycle
- reproductive system disease: Menorrhagia
- menstrual cycle
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What happens during the menstrual cycle?
The menstrual cycle involves recurring changes in hormone levels that cause physical changes in the uterus and ovaries, preparing the female body for pregnancy.
The cycle starts with the increasing secretion of follicle-stimulating hormone (FSH), which causes follicles to mature. As follicles mature, they secrete more estradiol, triggering a surge in luteinizing hormone (LH) secretion, causing the mature Graafian follicle to rupture. After ovulation, serum LH, FSH, and estradiol concentrations decrease, and the corpus luteum produces estrogen and progesterone. Decreasing estrogen and progesterone levels result in constriction of uterine arteries, interrupting oxygen and nutrient delivery to the endometrium, which is then sloughed off, causing menstruation. A new menstrual cycle then begins.
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Why does menstruation occur?
Menstruation occurs as part of the menstrual cycle, which prepares the endometrium for a possible pregnancy. The cycle has four phases: menstrual, postmenstrual, proliferative, and secretory.
Estrogen and progesterone stimulate the uterine lining to thicken. Ovulation occurs mid-cycle. If the egg is not fertilized, the corpus luteum degenerates, causing a drop in estrogen and progesterone. This leads to the breakdown of the endometrium, resulting in menstruation.
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What are common symptoms people experience during menstruation?
During menstruation, many women experience a range of physical and emotional symptoms, known as premenstrual syndrome (PMS). Physical symptoms include headaches, cramps, backaches, bloating, and changes in bowel habits like constipation or diarrhea. Emotionally, women may experience irritability, lethargy, mood swings, hostility, confusion, aggression, or depression. Some women also have sore breasts and pelvic discomfort. The severity of these symptoms varies among women, and they typically begin 7 to 14 days before menstruation, subsiding within 24 hours after it starts.
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How can menstruation affect a person's health and daily life?
Menstruation can affect a person's health and daily life in several ways. Many women experience premenstrual syndrome (PMS), a condition with physical and emotional symptoms that start 7 to 14 days before menstruation and end within 24 hours after it begins.
Physical symptoms of PMS include headaches, cramps, backaches, bloating, constipation or diarrhea, and breast soreness. Emotional and psychiatric symptoms range from irritability, lethargy, and mood swings to hostility, confusion, aggression, and depression. Some women suffer from dysmenorrhea, or painful menstruation, which can interfere with daily activities. Abnormal menstrual function can include excessive blood loss, irregular bleeding, or absence of menstruation.
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menstruation, periodic discharge from the vagina of blood, secretions, and disintegrating mucous membrane that had lined the uterus.
Biological significance
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 sheep, for example, there is only one breeding season in the year; during this season a cycle of changes takes place in the reproductive organs, characterized by ripening and release of ova from the ovaries, increased blood supply to the genital tract, growth of the uterus, and proliferation of its lining. There is a discharge of blood and mucus from the uterus and vagina, and this is the time when coition may take place. Pregnancy normally follows, but if the ewe is not served by the ram the changes retrogress until the next breeding season. This cycle of changes is termed the estrous cycle.
In many domesticated sheep there is more than one estrous cycle in the breeding season. If the ewe does not become pregnant in the first cycle there is a short resting phase; then ovulation is repeated and another cycle of activity of the reproductive system takes place. After each breeding period, with its succession of estrous cycles, there is a relatively long resting phase.
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In most female primates, including women, there is no resting phase; an unbroken series of estrous cycles occurs throughout the year, and pregnancy can occur in any one of them.
In some animals a variety of external stimuli act through the central nervous system on the hypothalamic region of the brain. The hypothalamus controls the release from the pituitary gland of hormones that induce ripening of ovarian follicles—ova and the cellular structures that enclose them. These pituitary hormones, called gonadotropic hormones, are carried to the ovaries by way of the bloodstream. In primates the hypothalamic mechanism normally is independent of external stimuli, and regular discharge of ova into the tubes leading to the uterus occurs even in the absence of coitus. Under the influence of the pituitary gonadotropic hormones, the ovary produces other hormones, which cause growth and increased vascularity of the uterus and vagina. These hormones are estrogens—chiefly 17 beta-estradiol—and progesterone. It is as though the ovary prepares the uterus for the reception of the ovum that is released in the particular cycle.
The menarche
The first menstruation, or menarche, usually occurs between ages 10 and 16, but in a few otherwise normal children menstruation may begin sooner or may be delayed. If the menstrual periods have not started by the age of 16 gynecological investigation is indicated. The menarche is preceded by other signs of estrogenic activity, such as enlargement of the breasts and the uterus and growth of pubic hair. The ovarian response to gonadotropic hormones may be erratic at first, so that irregular or heavy bleeding sometimes occurs, but this irregularity nearly always disappears spontaneously.