what hormone stimulates an egg to mature inside one of the ovaries
By definition, the menstrual cycle begins with the showtime day of bleeding, which is counted as day ane. The wheel ends only before the next menstrual catamenia. Menstrual cycles unremarkably range from nigh 25 to 36 days. Merely 10 to xv% of women have cycles that are exactly 28 days. Also, in at least 20% of women, cycles are irregular. That is, they are longer or shorter than the normal range. Commonly, the cycles vary the most and the intervals between periods are longest in the years immediately after menstruation starts (menarche) and before menopause.
Menstrual haemorrhage lasts 3 to vii days, averaging 5 days. Blood loss during a wheel normally ranges from ane/2 to 2 ane/2 ounces. A sanitary pad or tampon, depending on the type, can hold up to an ounce of blood. Menstrual claret, different blood resulting from an injury, commonly 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 has iii phases:
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Follicular (before release of the egg)
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Ovulatory (egg release)
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Luteal (after egg release)
Changes During the Menstrual Wheel
| The menstrual cycle is regulated past the complex interaction of hormones: luteinizing hormone, follicle-stimulating hormone, and the female sex hormones estrogen and progesterone . The menstrual cycle has three phases:
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 issue, 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. After in this phase, every bit 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 later on 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 nearly of this phase, the estrogen level is high. Progesterone and estrogen cause the lining of the uterus to thicken more than, to fix for possible fertilization. If the egg is not fertilized, the corpus luteum degenerates and no longer produces progesterone , the estrogen level decreases, the summit layers of the lining interruption down and are shed, and menstrual haemorrhage occurs (the first of a new menstrual wheel). If the egg is fertilized, the corpus luteum continues to function during early pregnancy. It helps maintain the pregnancy. |
The follicular phase begins on the beginning solar day of menstrual bleeding (day 1). Just the main event in this phase is the development of follicles in the ovaries.
At the beginning of the follicular phase, the lining of the uterus (endometrium) is thick with fluids and nutrients designed to nourish an embryo. If no egg has been fertilized, estrogen and progesterone levels are low. As a result, the height layers of the endometrium are shed, and menstrual bleeding occurs.
About this time, the pituitary gland slightly increases its product of follicle-stimulating hormone. This hormone then stimulates the growth of 3 to 30 follicles. Each follicle contains an egg. Subsequently in the phase, every bit the level of this hormone decreases, only one of these follicles (called the dominant follicle) continues to grow. Information technology soon begins to produce estrogen, and the other stimulated follicles brainstorm to suspension down. The increasing estrogen also begins to gear up the uterus and stimulates the luteinizing hormone surge.
On boilerplate, the follicular phase lasts about thirteen or 14 days. Of the iii phases, this phase varies the well-nigh in length. It tends to get shorter near menopause. This phase ends when the level of luteinizing hormone increases dramatically (surges). The surge results in release of the egg (ovulation) and marks the commencement of the next phase.
The ovulatory stage begins when the level of luteinizing hormone surges. Luteinizing hormone stimulates the dominant follicle to bulge from the surface of the ovary and finally rupture, releasing the egg. The level of follicle-stimulating hormone increases to a lesser degree. The office of the increase in follicle-stimulating hormone is non understood.
The ovulatory phase ordinarily lasts xvi to 32 hours. It ends when the egg is released, virtually 10 to 12 hours after the surge in the level of luteinizing hormone. The egg tin can exist fertilized for only up to about 12 hours after its release.
The surge in luteinizing hormone can be detected by measuring the level of this hormone in urine. This measurement can be used to determine when women are fertile. Fertilization is more than likely when sperm are nowadays in the reproductive tract before the egg is released. Most pregnancies occur when intercourse occurs within 3 days before ovulation.
Effectually the time of ovulation, some women feel a dull pain on one side of the lower belly. This pain is known as mittelschmerz (literally, middle pain). The pain may final for a few minutes to a few hours. The pain is normally felt on the aforementioned side every bit the ovary that released the egg, but the precise crusade of the pain is unknown. The pain may precede or follow the rupture of the follicle and may not occur in all cycles.
Egg release does not alternating betwixt the two ovaries and appears to be random. If 1 ovary is removed, the remaining ovary releases an egg every month.
The luteal phase begins after ovulation. Information technology lasts nearly 14 days (unless fertilization occurs) and ends simply before a menstrual period.
In this stage, the ruptured follicle closes after releasing the egg and forms a structure chosen a corpus luteum, which produces increasing quantities of progesterone . The progesterone produced past the corpus luteum does the following:
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Prepares the uterus in case an embryo is implanted
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Causes the endometrium to thicken, filling with fluids and nutrients to attend a potential embryo
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Causes the mucus in the neck to thicken, so that sperm or bacteria are less probable to enter the uterus
During most of the luteal phase, the estrogen level is high. Estrogen also stimulates the endometrium to thicken.
The increase in estrogen and progesterone levels causes milk ducts in the breasts to widen (dilate). Equally a event, the breasts may keen and become tender.
If the egg is not fertilized or if the fertilized egg does non implant, the corpus luteum degenerates subsequently 14 days, levels of estrogen and progesterone decrease, and a new menstrual bicycle begins.
If the embryo is implanted, the cells around the developing embryo brainstorm to produce a hormone called human being chorionic gonadotropin. This hormone maintains the corpus luteum, which continues to produce progesterone , until the growing fetus tin produce its own hormones. Pregnancy tests are based on detecting an increase in the human chorionic gonadotropin level.
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