menstruation

Menstruation



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Not to be confused with "mensuration", a
forestry term meaning measurement.


Menstrual cycle





Menstruation is the shedding of the uterine lining (endometrium).
It occurs on a regular basis in reproductive-age females of certain mammal
species. Overt menstruation (where there is bleeding from the uterus
through the vagina)
is found primarily in humans and close evolutionary relatives such as chimpanzees.^[1]
The females of other placental mammal species have estrous
cycles, in which the endometrium is reabsorbed by the animal
(covert menstruation) at the end of its reproductive cycle. Many
zoologists regard this as different from a "true" menstrual cycle.

Contents [hide] 1 Overview 2 As part of the menstrual cycle 3 Evolution 4 Culture and menstruation 5 Characteristics 5.1 Span 5.2 Physical experience 5.3 Emotional reactions 5.4 Flow 5.5 Duration 6 Menstrual products 7 Further reading 8 Footnotes

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[edit] Overview


Eumenorrhea expresses normal, regular menstruation that lasts
for a few days (usually 3 to 5 days, but anywhere from 2 to 7 days is
considered normal).^[2]
The average blood loss during menstruation is 35 millilitres with 10-80
mL considered normal;^[3]
many women also notice shedding of the endometrium
lining that appears as tissue mixed with the blood. (Sometimes this is
erroneously thought to indicate an early-term miscarriage of an embryo.)
An enzyme
called plasmin
— contained in the endometrium — tends to inhibit the blood from clotting. Because of this blood loss,
premenopausal women have higher dietary requirements for iron to
prevent iron deficiency. Many women
experience uterine cramps, also referred to
as dysmenorrhea, during this time, caused largely
by the contractions of the uterine muscle as it expels the endometrial
blood from the woman's body. A vast industry has grown to provide drugs
to aid in these cramps, as well as sanitary
products to help manage menses.
[edit] As part of the
menstrual cycle


Menstruation is the most visible phase of the menstrual cycle. Menstrual cycles are counted from the first
day of menstrual bleeding, because the onset of menstruation corresponds
closely with the hormonal cycle.
During pregnancy and for some time after childbirth,
menstruation is normally suspended; this state is known as amenorrhoea,
i.e. absence of the menstrual cycle. If menstruation has not resumed,
fertility is low during lactation. The average length of postpartum
amenorrhoea is longer when certain breastfeeding
practices are followed; this may be done intentionally as birth control
(lactational amenorrhea method).
[edit] Evolution


All female placental mammals have a uterine lining that builds
up when the animal is fertile, but is dismantled (menstruated) when the
animal is infertile. Some anthropologists have questioned the energy
cost of rebuilding the endometrium every fertility cycle. However,
anthropologist Beverly Strassmann has proposed that the energy savings
of not having to continuously maintain the uterine lining more
than offsets energy cost of having to rebuild the lining in the next
fertility cycle, even in species such as humans where much of the lining
is lost through bleeding (overt menstruation) rather than reabsorbed
(covert menstruation).^[1][4]
However, even in humans, much of it is re-absorbed.
Many have questioned the evolution of overt menstruation in humans
and related species, speculating on what advantage there could be to
losing blood associated with dismantling the endometrium rather than
absorbing it, as most mammals do.
Beginning in 1971, some research suggested that menstrual cycles of
co-habiting human females became synchronized. A few anthropologists
hypothesized that in hunter-gatherer societies, males would go on
hunting journeys whilst the females of the tribe were menstruating,
speculating that the females would not have been as receptive to sexual
relations while menstruating.^[5][6]
However, there is currently significant dispute as to whether menstrual synchrony exists.^[7]
Humans do, in fact, reabsorb about two-thirds of the endometrium each
cycle. Strassmann asserts that overt menstruation occurs not because it
is beneficial in itself. Rather, the fetal development of these species
requires a more developed endometrium, one which is too thick to
completely reabsorb. Strassman correlates species that have overt
menstruation to those that have a large uterus relative to the adult
female body size.^[1]
[edit] Culture and
menstruation

Main article: Culture and menstruation

Common usage refers to menstruation and menses as a period, a
contraction of "menstrual period". A woman might say that her "period is
late," or simply "I'm late," when an expected menstrual period has not
started. Delay or cessation of menstruation is commonly expected to be
the first indication to a woman that she may be pregnant. However, this cannot
be taken as certainty. Irregular cycles are common in the first few
years of menstruation. Regularity of the menstrual cycle may be also be
affected by physical or emotional stress. Moreover, continued
menstruation in early pregnancy is not uncommon.^[8]
Many religions have menstruation-related traditions. These may be
bans on certain actions during menstruation (such as intercourse in
orthodox Judaism, Hinduism and Islam), or rituals to be performed at the
end of each menses (such as the mikvah in Judaism and the ghusl in
Islam). Some traditional societies sequester females in residences,
"menstrual huts", that are reserved for that exclusive purpose until the
end of their menstrual period.
Since the late 1960s, some women have chosen to control the frequency
of menstruation with long-acting hormonal birth control. This allows
women to plan months in advance when she will menstruate as combined
hormone pills are taken in 28 day cycles, 21 hormonal pills with either a
7 day break from pills, or 7 placebo pills during which the woman
menstruates. Injections such as depo-provera became available in the 1960s,
progestogen implants such as Norplant
in the 1980s and extended cycle combined oral contraceptive pills
in the early 2000s.
[edit] Characteristics


[edit] Span


Menstruation will start at the onset of puberty
and end at the beginning of menopause.
[edit] Physical experience

See also: Premenstrual Syndrome

In many women, various intense sensations brought about by the
involved hormones and by cramping of the uterus can precede or accompany
menstruation. Stronger sensations may include significant menstrual pain (dysmenorrhea),
abdominal pain, migraine headaches, depression, emotional sensitivity, feeling
bloated, changes in sex drive and nausea. Breast
swelling and discomfort caused by premenstrual water retention or
hormone fluctuation is very common. Binge eating occurs in a minority
of menstruating women.^[9]
This may be due to fluctuation in beta-endorphin levels. More severe
symptoms may be classified as premenstrual dysphoric disorder
(PMDD). The sensations experienced vary from woman to woman and from
cycle to cycle.
[edit] Emotional reactions


Women may experience emotional disturbances associated with
menstruation. These range from the irritability popularly associated
with premenstrual syndrome (PMS), to
tiredness, or "weepiness" (i.e. tears of emotional closeness). A similar
range of emotional effects and mood swings is associated with pregnancy.^[10]
Rarely, in individuals susceptible to psychotic episodes, menstruation
may be a trigger (menstrual psychosis).
[edit] Flow


The normal menstrual flow follows a "crescendo-decrescendo" pattern;
that is, it starts at a moderate level, increases somewhat, and then
slowly tapers. Sudden heavy flows or amounts in excess of 80 mL (hypermenorrhea
or menorrhagia) may stem from hormonal
disturbance, uterine abnormalities, including uterine leiomyoma
or cancer,
and other causes. Doctors call the opposite phenomenon, of bleeding
very little, hypomenorrhea.
[edit] Duration


The typical woman bleeds for two to seven days at the beginning of
each menstrual cycle.^[2][11]
Prolonged bleeding (metrorrhagia, also meno-metrorrhagia)
no longer shows a clear interval pattern. Dysfunctional uterine bleeding
is hormonally caused bleeding abnormalities. Dysfunctional uterine
bleeding typically occurs in premenopausal women who do not ovulate
normally (i.e. are anovulatory). All these
bleeding abnormalities need medical attention; they may indicate hormone
imbalances, uterine fibroids, or other problems. As pregnant patients
may bleed, a pregnancy test forms part of the evaluation
of abnormal bleeding.
[edit] Menstrual products

Main article: Menstrual product

Most women use something to absorb or catch their menses. There are a
number of different methods available.
Disposable items:

• Sanitary napkins (Sanitary towels) or pads —
  Somewhat rectangular pieces of material worn in the underwear to absorb
  menstrual flow, often with "wings," pieces that fold around the
  undergarment and/or an adhesive backing to hold the pad in place.
  Disposable pads may contain wood pulp or gel products,
  usually with a plastic lining and bleached. Some sanitary napkins,
  particularly older styles, are held in place by a belt-like apparatus,
  instead of adhesive or wings.
  
• Tampons
  — Disposable cylinders of treated rayon/cotton
  blends or all-cotton fleece, usually bleached, that are inserted into
  the vagina to absorb menstrual flow.
  
• Padettes — Disposable wads of treated rayon/cotton blend fleece that
  are placed within the inner labia to absorb menstrual flow.
  
• Disposable menstrual cups — A firm,
  flexible cup-shaped device worn inside the vagina to catch menstrual
  flow. Disposable cups are made of soft plastic.
  

Reusable items:

• Reusable cloth pads are made of cotton
  (often organic), terrycloth,
  or flannel,
  and may be handsewn (from material or reused old clothes and towels) or
  storebought.
  
• Menstrual cups — A firm, flexible bell-shaped
  device worn inside the vagina to catch menstrual flow. Reusable versions
  include rubber or silicone cups.
  
• Sea sponges — Natural sponges, worn internally
  like a tampon to absorb menstrual flow.
  
• Padded panties — Reusable cloth (usually cotton) underwear
  with extra absorbent layers sewn in to absorb flow.
  
• Blanket,
  towel —
  (also known as a draw sheet) — large reusable piece of cloth, most often
  used at night, placed between legs to absorb menstrual flow.
  

In addition to products to contain the menstrual flow, pharmaceutical
companies likewise provide products — commonly non-steroidal
anti-inflammatory drugs (NSAIDs) — to relieve menstrual cramps. Some
herbs, such as dong quai, raspberry
leaf and crampbark, are also claimed to relieve menstrual pain;^[12]
however there is no documented scientific evidence to prove this

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