Related topics: women

Researchers solve mystery of long elephant pregnancy

(Phys.org) -- For years biologists have puzzled over how it is that elephants are able to maintain such long pregnancies, which typically run to nearly two years. While many theories have been tossed around, no one really ...

Apps send intimate user data to Facebook: report

A news report Friday said many smartphone apps were sending highly personal information such as menstrual cycles and body weight to Facebook, without notifying users.

Study shows how menstrual cycle affects consumer behavior

If cramps, mood swings and ice cream binges are what come to mind when you hear the hackneyed phrase that time of the month, think again. Researchers at Concordia University are taking a new look at the menstrual cycle by ...

Rodent with a human-like menstrual cycle found

(Phys.org)—A team of researchers working at Monash University in Australia has found an example of a rodent that has a human-like menstrual cycle. As the team notes in their paper uploaded to the preprint server bioRxiv, ...

Researcher finds gender differences in seasonal auditory changes

Auditory systems differ between sexes in sparrows depending on the season, a Georgia State University neuroscientist has found. The work adds to our knowledge of how the parts of the nervous system, including that of humans, ...

Toward a diagnostic blood test for endometriosis

Endometriosis is a chronic, often painful disease affecting up to 10 percent of women of reproductive age in the U.S. How it develops is not well understood, and detecting it with certainty requires surgery. But now, scientists ...

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Menstrual cycle

The menstrual cycle is a cycle of physiological changes that occurs in fertile females. Overt menstruation (where there is blood flow from the vagina) occurs primarily in humans and close evolutionary relatives such as chimpanzees. Females of other species of placental mammal undergo estrous cycles, in which the endometrium is completely reabsorbed by the animal (covert menstruation) at the end of its reproductive cycle. This article focuses on the human menstrual cycle.

The menstrual cycle, under the control of the endocrine system, is necessary for reproduction. It may be divided into three distinct phases: menstruation, the follicular phase and the luteal phase. Ovulation defines the transition from the follicular phase to the luteal phase. The length of each phase varies from woman to woman and cycle to cycle, though the average menstrual cycle is 28 days. Hormonal contraception interferes with the normal hormonal changes with the aim of preventing reproduction.

Stimulated by gradually increasing amounts of estrogen in the follicular phase, menses slow then stop, and the lining of the uterus thickens. 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 (non-dominant follicles atrophy and die). Approximately mid-cycle, 24-36 hours after the Luteinizing Hormone (LH) surges, the dominant follicle releases an ovum, or egg in an event called ovulation. After ovulation, the egg only lives for 24 hours or less without fertilization while the remains of the dominant follicle in the ovary become a corpus luteum; this body has a primary function of producing large amounts of progesterone. Under the influence of progesterone, the endometrium (uterine lining) changes to prepare for potential implantation of an embryo to establish a pregnancy. If implantation does not occur within approximately two weeks, the corpus luteum will involute, causing sharp drops in levels of both progesterone and estrogen. These hormone drops cause the uterus to shed its lining in a process termed menstruation.

In the menstrual cycle, changes occur in the female reproductive system as well as other systems (which lead to breast tenderness or mood changes, for example). A woman's first menstruation is termed menarche, and occurs typically around age 12. The end of a woman's reproductive phase is called the menopause, which commonly occurs somewhere between the ages of 45 and 55.

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