Natural changes in the human female reproductive system
This article is about biological aspects of the reproductive cycle in humans. For information specific to monthly periods, see menstruation and menstruation (mammal).
Menstrual cycle
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 makes 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 an embryo. These cycles are concurrent and coordinated, normally last between 21 and 35 days, 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 (endometrium) to thicken to accommodate an embryo should fertilization occur. The blood supply of the thickened lining 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 either in the ovary (ovarian cycle) or in the uterus (uterine cycle). The ovarian cycle consists of the follicular phase, ovulation, and 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. Menarche (the onset of the first period) usually occurs around the age of 12 years.
The menstrual cycle can cause some women to experience premenstrual syndrome with symptoms that may include tender breasts, and tiredness. More severe symptoms that affect daily living are classed as premenstrual dysphoric disorder, and are experienced by 3–8% of women. During the first few days of menstruation some women experience period pain that can spread from the abdomen to the back and upper thighs. The menstrual cycle can be modified by hormonal birth control.
The menstrualcycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system...
tissue from the inner lining of the uterus through the vagina. The menstrualcycle is characterized by the rise and fall of hormones. Menstruation is...
who begin living together in close proximity would experience their menstrualcycle onsets (the onset of menstruation or menses) becoming more synchronized...
that have estrous cycles resorb the endometrium if conception does not occur during that cycle. Mammals that have menstrualcycles shed the endometrium...
A menstrual pad, or simply a pad, (also known as a sanitary pad, sanitary towel, sanitary napkin or feminine napkin) is an absorbent item worn in the...
menstrual disorder is characterized as any abnormal condition with regards to a woman's menstrualcycle. There are many different types of menstrual disorders...
Irregular menstruation is a menstrual disorder whose manifestations include irregular cycle lengths as well as metrorrhagia (vaginal bleeding between...
a normal discomfort of the menstrualcycle, these symptoms must interfere with daily living, during two menstrualcycles of prospective recording. These...
A menstrual cup is a menstrual hygiene device which is inserted into the vagina during menstruation. Its purpose is to collect menstrual fluid (blood from...
(mēn) 'month', and ἀρχή (arkhē) 'beginning') is the first menstrualcycle, or first menstrual bleeding, in female humans. From both social and medical...
the menstrualcycle, after the follicular phase. The days in which a woman is most fertile can be calculated based on the date of the last menstrual period...
is involved in the regulation of female reproductive cycles such as estrous and menstrualcycles. Estradiol is responsible for the development of female...
the first part of the previous menstrualcycle. Proliferation is induced by estrogen (follicular phase of menstrualcycle), and later changes in this layer...
after the ovulation. This cycle has been associated with changes in a woman's testosterone levels during the menstrualcycle. According to Gabrielle Lichterman...
view of the fact that in humans, the menstrualcycle quite closely approximates the moon's 29.5-day synodic cycle, unlike in chimpanzees (~36 days) or...
and birth. It also channels menstrual flow, which occurs in humans and closely related primates as part of the menstrualcycle. Although research on the...
proliferative phase, is the phase of the estrous cycle (or, in primates for example, the menstrualcycle) during which follicles in the ovary mature from...
size, shape, and weight due to hormonal changes during puberty, the menstrualcycle, pregnancy, breastfeeding, and menopause. The breast is an apocrine...
The menstrualcycle is on average 28 days in length. It begins with menses (day 1–7) during the follicular phase (day 1–14), followed by ovulation (day...
of discharge varies between individuals and can vary throughout the menstrualcycle and throughout the stages of sexual and reproductive development. Normal...
follicles into large preovulatory follicles that occurs in part during the menstrualcycle. Contrary to male spermatogenesis, which can last indefinitely, folliculogenesis...
rate, as long as it results in ejaculation into the vagina. A woman's menstrualcycle begins, as arbitrarily assigned, with menses. Next is the follicular...
normal menstrualcycle is 21–35 days in duration, with bleeding lasting an average of 5 days and total blood flow between 25 and 80 mL. Heavy menstrual bleeding...
mammals, it manifests as the formation of an embryo from a subsequent menstrualcycle, while another embryo or fetus is already present in the uterus. When...
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