Menstrual cycle

By: Dr. Zeinab Hakim25-03-13

Menstrual Cycle

The menstrual cycle is the scientific term for the physiological changes that occur in fertile women and other female primates for the purposes of sexual reproduction.

The menstrual cycle, under the control of the endocrine system, is necessary for reproduction.

It is commonly divided into 3 phases:

• Follicular phase • Ovulation • Luteal phase

Menstruation

Menstruation is also called menstrual bleeding, menses, catamenia or a period.

Eumenorrhea denotes normal, regular menstruation that lasts for a few days (usually 3 to 5 days, but anywhere from 2 to 7 days is considered normal).

The average blood loss during menstruation is 35 milliliters with 10–80 ml considered normal.

Follicular phase This phase is also called the proliferative phase because a hormone causes the lining of the uterus to grow, or proliferate, during this time.

Through the influence of a rise in follicle stimulating hormone (FSH) during the first days of the cycle, a few ovarian follicles are stimulated. These follicles, which were present at birth and have been developing in a process known as folliculogenesis, compete with each other for dominance. Under the influence of several hormones, all but one of these follicles will stop growing, while one dominant follicle in the ovary will continue to maturity. The follicle that reaches maturity is called a tertiary, or Graafian follicle, and it contains the ovum.

As they mature, the follicles secrete increasing amounts of estradiol (an estrogen). The estrogens initiate the formation of a new layer of endometrium in the uterus, histologically identified as the proliferative endometrium.

Ovulation During the follicular phase, estradiol suppresses production of luteinizing hormone (LH) from the anterior pituitary gland.

When the egg has nearly matured, levels of estradiol reach a threshold above which this effect is reversed and estrogen actually stimulates the production of a large amount of LH.

This process, known as the LH surge, starts around day 12 of the average cycle and may last 48 hours.

Luteal phase The luteal phase is also called the secretory phase.

After ovulation, the pituitary hormones FSH and LH cause the remaining parts of the dominant follicle to transform into the corpus luteum, which produces progesterone.

Progesterone plays a vital role in making the endometrium receptive to implantation of the blastocyst and supportive of the early pregnancy, by increasing blood flow and uterine secretions and reducing the contractility of the smooth muscle in the uterus.

It also has the side effect of raising the woman's basal body temperature.

Consequently, the level of FSH and LH fall quickly over time, and the corpus luteum subsequently atrophies. Falling levels of progesterone trigger menstruation and the beginning of the next cycle.

From the time of ovulation until progesterone withdrawal has caused menstruation to begin, the process typically takes about two weeks, with 14 days considered normal.

For an individual woman, the follicular phase often varies in length from cycle to cycle, BUT, the length of her luteal phase will be fairly consistent from cycle to cycle.

Cycle length The length of a woman's menstrual cycle will typically vary, with some shorter cycles and some longer cycles.

A woman who experiences variations of less than eight days between her longest cycles and shortest cycles is considered to have regular menstrual cycles.

Length variation between eight and 20 days is considered as moderately irregular cycles.

Variation of 21 days or more between a woman's shortest and longest cycle lengths is considered very irregular.

Menstrual phases

Name of phase Average start dayassuming a 28-day cycle Average end day Average duration

number of days

Menstrual phase (Menstruation) 1 4 4

Proliferative phase (Some sources include Menstruation

in this phase)5 13 9

Ovulatory phase (Ovulation) 13 16 4

Luteal phase (also known as Secretory phase) 16 28 13

Ischemic phase 27 28 2

Proliferative phase 1 13 13

Menarche

First menstrual bleeding, in female humans.

From both social and medical perspectives, it is often considered the central event of female puberty, as it signals the possibility of fertility.

The average age of menarche in humans is 12–13 years, but is normal anywhere between ages 8 and 16.

Menopause The cessation of menstrual cycles at the end of a woman's reproductive period is termed menopause.

The average age of menopause in women is 52 years, with anywhere between 45 and 55 being common.

Disorders of ovulation

Disorders of ovulation include: oligoovulation and anovulation:

• Oligoovulation is infrequent or irregular ovulation (usually defined as cycles of ≥36 days or <8 cycles a year)

• Anovulation is absence of ovulation when it would be normally expected. Anovulation usually manifests itself as irregularity of menstrual periods, that is, unpredictable variability of intervals, duration, or bleeding.

Disorders of cycle length

• Irregular menstruation is where there is variation in menstrual cycle length of more than approximately eight days for a woman. The term metrorrhagia is often used for irregular menstruation that occurs between the expected menstrual periods.

• Polymenorrhea is the medical term for cycles with intervals of 21 days or fewer.

• Oligomenorrhea is the medical term for infrequent, often light menstrual periods (intervals exceeding 35 days).

• Amenorrhea is the absence of a menstrual period in a woman of reproductive age. Physiologic states of amenorrhea are seen during pregnancy and lactation (breastfeeding). Outside of the reproductive years there is absence of menses during childhood and after menopause

Disorders of flow

• Hypomenorrhea is abnormally light menstrual periods.

• Menorrhagia (meno = month, rrhagia = excessive flow/discharge) is an abnormally heavy and prolonged menstrual period.

• menometrorrhagia (meno = prolonged, metro = uterine, rrhagia = excessive flow/discharge)is when there is excessive menstrual and uterine bleeding other than that caused by menstruation.

Dysmenorrhea

• Dysmenorrhea (or dysmenorrhoea), cramps or painful menstruation, involves menstrual periods that are accompanied by either sharp, intermittent pain or dull, aching pain, usually in the pelvis or lower abdomen.

PMS• Premenstrual syndrome (PMS) is a consistent

pattern of emotional and physical symptoms occurring only during the luteal phase of the menstrual cycle that are of "sufficient severity to interfere with some aspects of life“. Physical symptoms such as bloating or breast tenderness.

Mittelschmerz • Mittelschmerz (German: "middle pain")

ovulation pain or midcycle pain is characterized by lower abdominal and pelvic pain that occurs roughly midway through a woman's menstrual cycle

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