The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that make pregnancy possible. The ovarian cycle controls the production and release of eggs and the cyclic release of estrogen and blogger.com uterine cycle governs the preparation and maintenance of the lining of the uterus (womb) to May 13, · Objective To estimate the real world effectiveness of the Pfizer-BioNTech BNTb2 and Oxford-AstraZeneca ChAdOx1-S vaccines against confirmed covid symptoms (including the UK variant of concern B), admissions to hospital, and deaths. Design Test negative case-control study. Setting Community testing for covid in England The design of experiments (DOE, DOX, or experimental design) is the design of any task that aims to describe and explain the variation of information under conditions that are hypothesized to reflect the blogger.com term is generally associated with experiments in which the design introduces conditions that directly affect the variation, but may also refer to the design of quasi-experiments
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The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that make pregnancy possible. The ovarian cycle controls the production and release of eggs and the cyclic release of estrogen and progesterone. The uterine cycle governs the preparation and maintenance of the lining of the uterus womb to receive a fertilized egg.
These cycles are concurrent and coordinated, normally last between 21 and 35 days in adult women, with a median length of 28 days, and continue for about 30—45 years. Naturally occurring hormones drive the cycles; the cyclical rise and fall of the follicle stimulating hormone prompts the production and growth of oocytes immature egg cells.
The hormone estrogen stimulates the uterus lining to thicken to accommodate an embryo should fertilization occur. The blood supply of the thickened lining endometrium provides nutrients to a successfully implanted embryo.
If implantation does not occur, the lining breaks down and blood is released. Triggered by falling progesterone levels, menstruation a "period", in common parlance is the cyclical shedding of the lining, and is a sign that pregnancy has not occurred. Each cycle occurs in phases based on events in the ovary ovarian cycle or the uterus uterine cycle. The ovarian cycle consists of the follicular phaseovulationand the luteal phase ; the uterine cycle consists of the menstrual, proliferative and secretory phases.
Day one of the menstrual cycle is the first day of the period, which lasts for about five days. Around day fourteen, an egg is usually released from the ovary, simmons laboratories case study summary. Menarche the onset of the first period usually occurs around the age of twelve years, simmons laboratories case study summary.
The menstrual cycle can cause some women to experience problems that disrupt daily lives. These can include crampstender breasts, tiredness, simmons laboratories case study summary premenstrual syndrome. The menstrual cycle can be modified by hormonal birth control. The menstrual cycle encompasses the ovarian and uterine cycles. The ovarian cycle describes changes that occur in the follicles of the ovary[1] whereas the uterine cycle describes changes in the endometrial lining of the uterus.
Both cycles can be divided into phases. The ovarian cycle consists of alternating follicular and luteal phasesand the uterine cycle consists of menstruationthe proliferative phase, and the secretory phase.
The hypothalamus releases gonadotropin-releasing hormone GnRHwhich causes the nearby anterior pituitary gland to release follicle-stimulating hormone FSH and luteinizing hormone LH. Before pubertyGnRH is released in low steady quantities and at a steady simmons laboratories case study summary. After puberty, GnRH is released in large pulses, and the frequency and magnitude of these determine how much FSH and LH are produced by the pituitary.
Measured from the first day of one menstruation to the first day of the next, the length of a menstrual cycle varies but has a median length of 28 days.
Between menarche and menopause the human ovaries regularly alternate between luteal and follicular phases during the monthly menstrual cycle. Follicles in the ovary begin developing under the influence of a complex interplay of hormones, and after several days one, or occasionally two, become dominant, while non-dominant follicles shrink and die.
About mid-cycle, some 10—12 hours after the luteinizing hormone LH surges, [4] the dominant follicle releases an oocytein an event called ovulation. After ovulation, the oocyte lives for 24 hours or less simmons laboratories case study summary fertilization[11] while the remains of the dominant follicle in the ovary become a corpus luteum — a body with the primary function of producing large amounts of the hormone progesterone.
Simmons laboratories case study summary thickness of the endometrium continues to increase in response to mounting levels of estrogen, which is released by the antral follicle a mature ovarian follicle into the blood circulation, simmons laboratories case study summary. Peak levels of estrogen are reached at around day thirteen of the cycle and coincide with ovulation.
If implantation does not occur within about two weeks, the corpus luteum degenerates into the corpus albicanswhich does not produce hormones, causing a sharp drop in levels of both progesterone and estrogen. This drop causes the uterus to lose its lining in menstruation; it is around this time that the lowest levels of estrogen are reached.
In an ovulatory menstrual cycle, the ovarian and uterine cycles are concurrent and coordinated and last between 21 and 35 days in an adult woman, with a population average of 27—29 days.
The ovaries contain a finite number of egg stem cellsgranulosa cells and theca cellswhich together form primordial follicles. This decreases to around 2 million by the time a girl is born, andby the time she has her first simmons laboratories case study summary. On average, one egg matures and is released during ovulation each month after menarche.
The other cells are discarded as polar bodieswhich cannot be fertilized. During this phase usually only one ovarian follicle fully matures and gets ready to release an egg. Through the influence of a rise in follicle stimulating hormone FSH during the first days of the cycle, simmons laboratories case study summary, a few ovarian follicles are stimulated.
These follicles, simmons laboratories case study summary, which have been developing for the better part of a year in a process known as folliculogenesiscompete with each other for dominance. All but one of these follicles will stop growing, while one dominant follicle — the one that has the most FSH receptors — will continue to maturity. The remaining follicles die in a process called follicular atresia.
The follicle that reaches maturity is called an antral follicle, and it contains the ovum egg cell. The theca cells develop receptors that bind LH, simmons laboratories case study summary, and in response secrete large amounts of androstenedione. At the same time the granulosa cells surrounding the maturing follicle develop receptors that bind FSH, and in response start secreting androstenedione, which is converted to estrogen by simmons laboratories case study summary enzyme aromatase.
The estrogen inhibits further production of FSH and LH by the pituitary gland. This negative feedback regulates levels of FSH and LH. The dominant follicle continues simmons laboratories case study summary secrete estrogen, and the rising estrogen levels make the pituitary more responsive to GnRH from the hypothalamus. As estrogen increases this becomes a positive feedback signal, which makes the pituitary secrete more FSH and LH.
This surge of FSH and LH usually occurs one to two days before ovulation and is responsible for stimulating the rupture of the antral follicle and release of the oocyte. Around day fourteen, the egg is released from the ovary. The release of LH matures the egg and weakens the follicle wall in the ovary, causing the fully developed follicle to release its oocyte.
If it is not fertilized by a sperm, the oocyte degenerates. The mature egg has a diameter of about 0. Which of the two ovaries — left or right — ovulates appears random; [30] no left and right coordinating process is known.
After about a day, an unfertilized egg disintegrates or dissolves in the fallopian tube, and a fertilized egg reaches the uterus in three to five days.
Fertilization usually takes place in the ampullathe widest section of the fallopian tubes. A fertilized egg immediately starts the process of embryogenesis development. The developing embryo takes about three days to reach the uterus, and another three days to implant into the endometrium. It has usually reached the blastocyst stage at the time of implantation: this is when pregnancy begins.
The syncytiotrophoblast the outer layer of the resulting embryo-containing blastocyst that later becomes the outer layer of the placenta produces human chorionic gonadotropin hCGwhich is very similar to LH and preserves the corpus luteum.
During the first few months of pregnancy, the corpus luteum continues to secrete progesterone and estrogens at slightly higher levels than those at ovulation.
After this and for the rest of the pregnancy, the placenta secretes high levels of these hormones — along with human chorionic gonadotropin hCGwhich stimulates the corpus luteum to secrete more progesterone and estrogens, blocking the menstrual cycle. Lasting about 14 days, [4] the simmons laboratories case study summary phase is the final phase of the ovarian cycle and it corresponds to the secretory phase of the uterine cycle.
During the luteal phase, the pituitary hormones FSH and LH cause the remaining parts of the dominant follicle to transform into the corpus luteum, which produces progesterone.
The hormones produced by the corpus luteum also suppress production of the FSH and LH that the corpus luteum needs to maintain itself. The level of FSH and LH fall quickly, and the corpus luteum atrophies. From the time of ovulation until progesterone withdrawal has caused menstruation to begin, the process typically takes about two weeks. For an individual woman, the follicular phase often varies in length from cycle to cycle; by contrast, the length of her luteal phase will be fairly consistent from cycle to simmons laboratories case study summary at 10 to 16 days average 14 days.
The uterine cycle has three phases: menses, proliferative and secretory. Menstruation also called menstrual bleeding, menses or a period is the first and simmons laboratories case study summary evident phase of the uterine cycle and first occurs at puberty. Called menarche, the first period occurs at the age of around twelve or thirteen years. Menstruation is initiated each month by falling levels of estrogen and progesterone and the release of prostaglandins[20] which constrict the spiral arteries.
This causes them to spasmcontract and break up. Later the whole layer is lost and only the bottom layer, the stratum basalis, is left in place. The flow of blood normally serves as a sign that a woman has simmons laboratories case study summary become pregnant, but this cannot be taken as certainty, as several factors can cause bleeding during pregnancy. The average age of menopause in women is 52 years, and it typically occurs between 45 and 55 years of age.
Eumenorrhea denotes normal, regular menstruation that lasts for around the first 5 days of the cycle. The proliferative phase is the second phase of the uterine cycle when estrogen causes the lining of the uterus to grow and proliferate. The estrogens initiate the formation of a new layer of endometrium in the uterus with the spiral arterioles.
As estrogen levels increase, cells in the cervix produce a type of cervical mucus [52] that has a higher pH and is less viscous than usual, rendering it more friendly to sperm. The secretory phase is the final phase of the uterine cycle and it corresponds to the luteal phase of the ovarian cycle.
During the secretory phase, the corpus luteum produces progesterone, simmons laboratories case study summary, which plays a vital role in making the endometrium receptive to the implantation of a blastocyst a fertilized egg, which has begun to grow. If pregnancy does not occur the ovarian and uterine cycles start over again. Only two thirds of overtly normal menstrual cycles are ovulatory, that is, cycles in which ovulation occurs. During the first two years following menarche, ovulation is absent in around half of cycles.
Stress, simmons laboratories case study summary, anxiety and eating disorders can cause a fall in GnRH, and a disruption of the menstrual cycle. Around menopause, hormone feedback dysregulation leads to anovulatory cycles, simmons laboratories case study summary. Although anovulation is not considered a disease, it can be a sign of an underlying condition such as polycystic ovary syndrome. These changes are reversible as the stressors decrease or, in the simmons laboratories case study summary of the simmons laboratories case study summary, as she adapts to the training.
Although a normal and natural process, [64] some women experience problems sufficient to disrupt their lives as a result of their menstrual cycle. There are common culturally communicated misbeliefs that the menstrual cycle affects women's moods, causes depression or irritability, or that menstruation is a painful, shameful or unclean experience. Often a woman's normal mood variation is falsely attributed to the menstrual cycle. Much of the research is weak, but there appears to be a very small increase in mood fluctuations during the luteal and menstrual phases, and a corresponding decrease during the rest of the cycle.
The result can be subtle physiological and observable changes to women's athletic performance including strength, aerobic, and anaerobic performance. In some women, ovulation features a characteristic pain [d] called mittelschmerz a German term meaning middle pain. The cause of the pain is associated with the ruptured follicle, causing a small amount of blood loss. Even when normal, the changes in hormone levels during the menstrual cycle can increase the incidence of disorders such as autoimmune diseasessimmons laboratories case study summary, [79] which might be caused by estrogen enhancement of the immune system.
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Feb 21, · The Chronic Care Model (CCM) uses a systematic approach to restructuring medical care to create partnerships between health systems and communities. The objective of this study was to describe how researchers have applied CCM in US primary care settings to provide care for people who have diabetes and to describe outcomes of CCM implementation The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that make pregnancy possible. The ovarian cycle controls the production and release of eggs and the cyclic release of estrogen and blogger.com uterine cycle governs the preparation and maintenance of the lining of the uterus (womb) to May 13, · Objective To estimate the real world effectiveness of the Pfizer-BioNTech BNTb2 and Oxford-AstraZeneca ChAdOx1-S vaccines against confirmed covid symptoms (including the UK variant of concern B), admissions to hospital, and deaths. Design Test negative case-control study. Setting Community testing for covid in England
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