These physical changes are regulated by changes in the For up to several years before and just after menopause, estrogen levels fluctuate widely, periods become irregular By definition, the menstrual cycle begins with the first day of bleeding, which is counted as day 1.
The cycle ends just before the next menstrual period. Menstrual cycles normally range from about 25 to 36 days. That is, they are longer or shorter than the normal range.
Usually, the cycles vary the most and the intervals between periods are longest in the years immediately after menstruation starts menarche and before menopause. Menstrual bleeding lasts 3 to 7 days, averaging 5 days.
A sanitary pad or tampon, depending on the type, can hold up to an ounce of blood. Menstrual blood, unlike blood resulting from an injury, usually does not clot unless the bleeding is very heavy. The menstrual cycle is regulated by hormones. Luteinizing hormone and follicle-stimulating hormone, which are produced by the pituitary gland, promote ovulation and stimulate the ovaries to produce estrogen and progesterone.
Estrogen and progesterone stimulate the uterus and breasts to prepare for possible fertilization. The menstrual cycle is regulated by the complex interaction of hormones: luteinizing hormone, follicle-stimulating hormone, and the female sex hormones estrogen and progesterone. The menstrual cycle begins with menstrual bleeding menstruation , which marks the first day of the follicular phase. When the follicular phase begins, levels of estrogen and progesterone are low.
As a result, the top layers of the thickened lining of the uterus endometrium break down and are shed, and menstrual bleeding occurs. About this time, the follicle-stimulating hormone level increases slightly, stimulating the development of several follicles in the ovaries. Each follicle contains an egg. Later in this phase, as the follicle-stimulating hormone level decreases, only one follicle continues to develop. This follicle produces estrogen.
The ovulatory phase begins with a surge in luteinizing hormone and follicle-stimulating hormone levels. Luteinizing hormone stimulates egg release ovulation , which usually occurs 16 to 32 hours after the surge begins. The estrogen level decreases during the surge, and the progesterone level starts to increase. During the luteal phase, luteinizing hormone and follicle-stimulating hormone levels decrease.
The ruptured follicle closes after releasing the egg and forms a corpus luteum, which produces progesterone. During most of this phase, the estrogen level is high. Stops FSH being produced so that only one egg matures in a cycle. Repairs, thickens and maintains the uterus lining.
Stimulates the pituitary gland to release LH. LH luteinising hormone. Triggers ovulation the release of a mature egg. Some women take hormone replacement therapy to replace both hormones, or they take estrogen alone. This helps relieve symptoms of menopause. Estrogen without enough progesterone may cause the lining of the uterus to thicken. This is called endometrial hyperplasia. In some cases of endometrial hyperplasia, the cells of the lining become abnormal.
This is called atypical hyperplasia. This condition can lead to cancer of the uterus. If you have abnormal bleeding along with any of the other risk factors, you may need to be tested for endometrial hyperplasia. One or more tests may be required. Your doctor may suggest you have a vaginal ultrasound exam. For this test, a small device is placed in your vagina. Fluid may be placed in your uterus. Ultrasound uses sound waves to make a picture of the uterine lining.
Endometrial hyperplasia also may be found with a biopsy of the endometrium. Your doctor puts a narrow tube inside the uterus to take a sample of cells. You may feel some cramping during the test. The cells will be sent to a lab and checked under a microscope. Endometrial biopsy results may detect cancer of the uterus. Dilation and Curettage. A special device called a curette is used to gently loosen and remove a sample of the uterine lining. This tissue then is studied in the lab to check for cancer.
If the egg is not fertilised, the corpus luteum breaks down, the production of progesterone falls and a new menstrual cycle begins. If the egg is fertilised, progesterone stimulates the growth of blood vessels that supply the lining of the womb endometrium and stimulates glands in the endometrium to secrete nutrients that nourish the early embryo.
Progesterone then prepares the tissue lining of the uterus to allow the fertilised egg to implant and helps to maintain the endometrium throughout pregnancy. During the early stages of pregnancy, progesterone is still produced by the corpus luteum and is essential for supporting the pregnancy and establishing the placenta.
During pregnancy, progesterone plays an important role in the development of the foetus it stimulates the growth of maternal breast tissue; prevents lactation ; and strengthens the pelvic wall muscles in preparation for labour. The level of progesterone in the body steadily rises throughout pregnancy until labour occurs and the baby is born. Although the corpus luteum in the ovaries is the major site of progesterone production in humans, progesterone is also produced in smaller quantities by the ovaries themselves, the adrenal glands and, during pregnancy, the placenta.
The formation of the corpus luteum which produces the majority of progesterone is triggered by a surge in luteinising hormone production by the anterior pituitary gland.
This normally occurs at approximately day 14 of the menstrual cycle and it stimulates the release of an egg from the ovary ovulation and the formation of the corpus luteum from the remnant of the follicle. The corpus luteum then secretes progesterone, which prepares the body for pregnancy. If the egg is not fertilised and no embryo is conceived, the corpus luteum breaks down and the production of progesterone decreases. As the lining of the womb is no longer maintained by progesterone from the corpus luteum, it breaks away and menstrual bleeding occurs, marking the start of a new menstrual cycle.
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