Menstruation is the technical term for getting your period. About once a month, females who have gone through puberty will experience menstrual bleeding. This happens because the lining of the uterus has prepared itself for a possible pregnancy by becoming thicker and richer in blood vessels. If pregnancy does not occur, this thickened lining is shed, accompanied by bleeding. Bleeding usually lasts for days. For most women, menstruation happens in a fairly regular, predictable pattern.
The length of time from the first day of one period to the first day of the next period normally ranges from days. The menstrual cycle is controlled by a complex orchestra of hormones, produced by two structures in the brain, the pituitary gland and the hypothalamus along with the ovaries. If you just want a quick, general overview of the menstrual cycle, read this description.
For a more detailed review of the physical and hormonal changes that happen over the menstrual cycle, click here. The menstrual cycle includes several phases. The exact timing of the phases of the cycle is a little bit different for every woman and can change over time.
Once the bleeding stops, the uterine lining also called the endometrium begins to prepare for the possibility of a pregnancy. Somewhere around day 14, an egg is released from one of the ovaries and begins its journey down the fallopian tubes to the uterus.
In this case the fertilized egg will travel to the uterus and attempt to implant in the uterine wall.
If the egg was not fertilized or implantation does not occur, hormonal changes signal the uterus to prepare to shed its lining, and the egg breaks down and is shed along with lining.
This phase of the menstrual cycle occurs from approximately day Day 1 is the first day of bright red bleeding, and the end of this phase is marked by ovulation. While menstrual bleeding does happen in the early part of this phase, the ovaries are simultaneously preparing to ovulate again.
The pituitary gland located at the base of the brain releases a hormone called FSH — follicle stimulating hormone. Eventually, one of these follicle becomes dominant and within it develops a single mature egg; the other follicles shrink back. If more than one follicle reaches maturity, this can lead to twins or more. The maturing follicle produces the hormone estrogen, which increases over the follicular phase and peaks in the day or two prior to ovulation.
The lining of the uterus endometrium becomes thicker and more enriched with blood in the second part of this phase after menstruation is over , in response to increasing levels of estrogen. The egg travels down the fallopian tube toward the uterus to be fertilized by sperm. The ovulation phase is the only time during your menstrual cycle when you can get pregnant.
Ovulation happens at around day 14 if you have a day cycle — right in the middle of your menstrual cycle. It lasts about 24 hours. Because sperm can live up to five days, pregnancy can occur if a woman has sex as much as five days prior to ovulation.
After the follicle releases its egg, it changes into the corpus luteum. This structure releases hormones, mainly progesterone and some estrogen. The rise in hormones keeps your uterine lining thick and ready for a fertilized egg to implant. If you do get pregnant, your body will produce human chorionic gonadotropin hCG.
This is the hormone pregnancy tests detect. It helps maintain the corpus luteum and keeps the uterine lining thick. This leads to decreased levels of estrogen and progesterone, which causes the onset of your period. The uterine lining will shed during your period. These include:. The luteal phase lasts for 11 to 17 days. The average length is 14 days. Some women get their period at the same time each month. Others are more irregular. The pain may last for a few minutes to a few hours.
The pain is usually felt on the same side as the ovary that released the egg, but the precise cause 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 alternate between the two ovaries and appears to be random. If one ovary is removed, the remaining ovary releases an egg every month. The luteal phase begins after ovulation. It lasts about 14 days unless fertilization occurs and ends just before a menstrual period. In this phase, the ruptured follicle closes after releasing the egg and forms a structure called a corpus luteum, which produces increasing quantities of progesterone.
The progesterone produced by the corpus luteum does the following:. Causes the endometrium to thicken, filling with fluids and nutrients to nourish a potential embryo. Causes the mucus in the cervix to thicken, so that sperm or bacteria are less likely to enter the uterus. Causes body temperature to increase slightly during the luteal phase and remain elevated until a menstrual period begins this increase in temperature can be used to estimate whether ovulation has occurred Overview of Infertility Infertility is usually defined as the inability of a couple to achieve a pregnancy after repeated intercourse without contraception for 1 year.
Frequent intercourse without birth control usually 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. As a result, the breasts may swell and become tender. If the egg is not fertilized or if the fertilized egg does not implant, the corpus luteum degenerates after 14 days, levels of estrogen and progesterone decrease, and a new menstrual cycle begins.
If the embryo is implanted, the cells around the developing embryo begin to produce a hormone called human chorionic gonadotropin. This hormone maintains the corpus luteum, which continues to produce progesterone , until the growing fetus can produce its own hormones.
Pregnancy tests are based on detecting an increase in the human chorionic gonadotropin level. Merck and Co. From developing new therapies that treat and prevent disease to helping people in need, we are committed to improving health and well-being around the world. The Manual was first published in as a service to the community.
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If pregnancy does not occur, the corpus luteum withers and dies, usually around day 22 in a day cycle. The drop in progesterone levels causes the lining of the uterus to fall away.
This is known as menstruation. The cycle then repeats. This page has been produced in consultation with and approved by:. Alcohol is responsible for most drug-related deaths in the teenage population. Androgen deficiency in women and its treatment is controversial, and more research is needed.
It is helpful to imagine assertiveness as the middle ground between aggression and passivity. IVF in-vitro-fertilization and ICSI intracytoplasmic sperm injection are assisted reproductive treatment ART procedures in which fertilisation of an egg occurs outside the body.
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