"Boobs" redirects here. For other uses, see
boob.
right|300px|thumb|Pregnant human female's
breast The term breast refers to the upper ventral region of an animal’s torso,
particularly that of mammals, including human beings. The breasts
of a female mammal’s body contain the mammary glands, which secrete milk used to feed infants. This article deals with the human breast; for other animals, see udder and mammary gland.
Breasts are more visible on adult women, but male humans also have
breasts which, although usually less prominent, are structurally identical (homologous) to the female, as they develop embryologically from
the same tissues.
Anatomy
- See also: Human anatomy
The breasts are modified sudoriferous (sweat) glands, producing milk in females.[1] Each breast has one nipple surrounded by the
areola. The areola is colored from pink to dark brown and has several sebaceous glands. In females, the larger mammary glands within
the breast produce the milk. They are distributed throughout the breast, with two-thirds of the tissue found within 30 mm of
the base of the nipple.[2] These are drained to
the nipple by between 4 and 18 lactiferous ducts, where each duct has its own opening. The network formed by these ducts
is complex, like the tangled roots of a tree. It is not always arranged radially, and branches close to the nipple. The ducts
near the nipple do not act as milk reservoirs; Ramsay et al. have shown that conventionally described lactiferous
sinuses do not, in fact, exist.
The remainder of the breast is composed of connective tissue (collagen and elastin), adipose tissue
(fat), and Cooper's ligaments. The ratio of glands to adipose tissues rises from 1:1
in nonlactating women to 2:1 in lactating women.[2]
The breasts sit over the pectoralis major muscle and usually extend from the
level of the 2nd rib to the level of the 6th rib anteriorly. The superior lateral quadrant of the breast extends diagonally
upwards towards the axillae and is known as the tail of Spence. A thin layer of
mammary tissue extends from the clavicle above to the
seventh or eighth ribs below and from the midline to the edge of the latissimus
dorsi posteriorly. (For further explanation, see anatomical terms of
location.)
The arterial blood blood supply to the breasts is
derived from the internal thoracic artery (formerly called the internal
mammary artery), lateral thoracic artery, thoracoacromial artery, and posterior intercostal arteries. The venous drainage of the breast is mainly to the axillary vein, but there is
some drainage to the internal thoracic vein and the intercostal veins. Both sexes
have a large concentration of blood vessels and nerves in their nipples. The nipples of
both females and males can become erect in response to sexual stimuli,[3] and also to cold.
The breast is innervated by the anterior and lateral cutaneous branches of
the fourth through sixth intercostal nerves. The nipple is supplied by the T4 dermatome.
Lymphatic drainage
About 75% of lymph from the breast travels to the ipsilateral axillary lymph nodes. The rest travels to parasternal nodes, to the other breast, or abdominal lymph nodes. The
axillary nodes include the pectoral, subscapular, and humeral groups of lymph nodes. These drain to the central axillary lymph nodes, then to the apical axillary lymph nodes. The lymphatic drainage of the
breasts is particularly relevant to oncology, since breast
cancer is a common cancer and cancer cells can break away from a tumour and spread to other parts of the body through the lymph system by metastasis.
Shape and support
Relatively round breasts which protrude almost horizontally.
Breasts vary in both size and shape, and their external appearance is not predictive of their internal anatomy or lactation
potential. The shape of a woman’s breasts is in large part dependent on their support, which primarily comes from the Cooper's
ligaments, and the underlying chest on which they rest. The breast is attached at its base to the chest wall by the deep fascia
over the pectoral muscles. On its upper surface it is given some support by the covering skin where it continues on to the upper
chest wall. It is this support which determines the shape of the breasts. In a small fraction of women, the frontal milk sinuses
(ampulla) in the breasts are not flush with the surrounding breast tissue, which causes the sinus area to visibly bulge
outward.
In discussing the support of breasts, it is helpful to draw a distinction between breasts which rest on the chest below, and
those which do not. High, rounded breasts protrude almost horizontally from the chest wall. All breasts are like this in early
stages of development, and such a shape is common in younger women and girls. This protruding or “high” breast is anchored to the
chest at its base, and the weight is distributed evenly over the area of the base of the approximately dome- or cone-shaped
breasts. [citation needed]
In the “low” breast, a proportion of the breasts’ weight is actually supported by the chest against which the lower breast
surface comes to rest, as well as the deep anchorage at the base. The weight is thus distributed over a larger area, which has
the effect of reducing the strain. In both males and females, the thoracic cavity slopes
progressively outwards from the thoracic inlet (at the top of the breastbone) above to the
lowest ribs which mark its lower boundary, allowing it to support the breasts.
The inframammary fold (or line, or crease) is an anatomic structure created by
adherence between elements in the skin and underlying connective tissue[4] and represents the inferior extent of breast anatomy. Some teenagers may develop breasts
whose skin comes into contact with the chest below the fold at an early age, and some women may never develop such breasts; both
situations are perfectly normal. The relationship of the nipple position to the fold is described as ptosis, a term also applied to other body parts and which refers in general to drooping or sagging. Due
to breast weight and relaxation of support structures, the nipple-areola complex and breast tissue may eventually hang below the
fold, and in some cases the breasts may extend as far as, or even beyond, the navel. The length from the nipple to the sternal
notch (central, upper border) in the youthful breast averages 21 cm and is a common anthropometric figure used to assess both breast symmetry and ptosis. Lengthening of both this measurement
and the distance between the nipple and the fold are both characteristic of advancing grades of ptosis.
The end of the breast, which includes the nipple, may either be flat (a 180 degree angle) or angled (angles lower than 180
degrees). Breast ends are rarely angled sharper than 60 degrees. Angling of the end of the breast is caused in part by the
ligaments that suspend it, such that the breast ends often have a more obtuse angle when a woman is lying on her back. Breasts
exist in a range of ratios between length and base diameter, usually ranging from 1/2 to 1.
Development
-
The development of a girl's breasts during puberty is triggered by sex hormones, chiefly estrogen. This hormone has been demonstrated to
cause the development of woman-like, enlarged breasts in men, a condition called gynecomastia, and is sometimes used deliberately for this effect in male-to-female sex change hormone replacement
therapy.
In most cases, the breasts fold down over the chest wall during Tanner stage
development, as shown in this diagram.[5] It is typical for a woman’s breasts to be unequal in size particularly while the breasts
are developing. Statistically it is slightly more common for the left breast to be the larger.[6] In rare cases, the breasts may be significantly different in size,
or one breast may fail to develop entirely.
A large number of medical conditions are known to cause abnormal development of the breasts during puberty. Virginal breast hypertrophy is a condition which involves excessive growth of the breasts,
and in some cases the continued growth beyond the usual pubescent age. Breast hypoplasia is a
condition where one or both breasts fail to develop.
In Cameroon, some girls are subjected to breast
ironing to stunt breast growth in order to make them less sexually attractive in the belief that this makes them less
likely to become a victim of rape.
Changes
thumb|right|Breast with visible
stretchmarks.
As breasts are mostly composed of adipose tissue, their size can change over time. This occurs for a number of reasons, most
obviously when a girl grows during puberty and when a woman becomes pregnant. The breast size may also change if she gains (or loses) weight
for any other reason. Any rapid increase in size of the breasts can result in the appearance of stretchmarks.
It is typical for a number of other changes to occur during pregnancy: in addition to becoming larger, the breasts generally
become firmer, mainly due to hypertrophy of the mammary gland in response to the
hormone prolactin. The size of the nipples may increase
noticeably and their pigmentation may become darker. These changes may continue during breastfeeding. The breasts generally revert to approximately their previous size after pregnancy, although
there may be some increased sagging and stretchmarks.
The size of a woman’s breasts usually fluctuates during the menstrual cycle,
particularly with premenstrual water retention. An increase in breast size
is a common side effect of use of the combined oral contraceptive pill.
The breasts naturally sag through aging, as the ligaments
become elongated.
Function
Breastfeeding
-
The breasts of a woman who is six months pregnant.
[7]
The primary function of mammary glands is to nurture young by producing
breast milk. The production of milk is called lactation.
(While the mammary glands that produce milk are present in the male, they normally remain undeveloped.) The orb-like shape of
breasts may help limit heat loss, as a fairly high temperature is required for the production of milk. Alternatively, one theory
states that the shape of the human breast evolved in order to prevent infants from suffocating while feeding.[8] Since human infants do not have a protruding jaw
like human evolutionary ancestors and other primates, the infant’s nose might be blocked by a flat female chest while
feeding.[8] According to this theory, as the
human jaw receded, the breasts became larger to compensate.[8]
Milk production unrelated to pregnancy can also occur. This galactorrhea may be an
adverse effect of some medicinal drugs (such as some antipsychotic
medication), extreme physical stress or endocrine disorders. If it occurs in men it is called male lactation. Newborn babies are often capable of lactation because they receive the hormones
prolactin and oxytocin via the mother's bloodstream,
filtered through the placenta. This neonatal liquid is known colloquially as witch's milk.
Sexual role
Breasts play an important part in human sexual behavior. They are one of most
visible or obvious female secondary sex characteristics,[9] and play an important role in sexual
attraction of partners, and pleasure of the individual. On sexual arousal breast
size increases, venous patterns across the breasts become more visible, and nipples harden. During
sexual intercourse it is common practice to press or massage breasts with hands. Oral stimulation of nipples and breasts is also common. Some women can achieve
breast orgasms. In the ancient Indian work the
Kama Sutra, marking breasts with nails and biting with teeth are explained as
erotic[10].
Other suggested functions
Zoologists point out that no female mammal other than the human has breasts of comparable
size, relative to the rest of the body, when not lactating and that humans are the only primate
that has permanently swollen breasts. This suggests that the external form of the breasts is connected to factors other than
lactation alone.
One theory is based around the fact that, unlike nearly all other primates, human females do not display clear, physical signs
of ovulation. This could have plausibly resulted in human males evolving to respond to more
subtle signs of ovulation. During ovulation, the increased estrogen present in the female body
results in a slight swelling of the breasts, which then males could have evolved to find attractive. In response, there would be
evolutionary pressures that would favor females with more swollen breasts who would, in a manner of speaking, appear to males to
be the most likely to be ovulating.
Some zoologists (notably Desmond Morris) believe that the shape of female breasts
evolved as a frontal counterpart to that of the buttocks, the reason being that whilst other
primates mate in the rear-entry position, humans are more likely to successfully
copulate by mating face to face, the so-called missionary
position. A secondary sexual characteristic on a woman’s chest would have encouraged this in more primitive incarnations
of the human race, and a face on encounter may have helped found a relationship between partners beyond merely a sexual
one.[11]
Cultural status
In art, religion, and legend
Historically, breasts have been regarded as fertility symbols, because they are the
source of life-giving milk. Certain prehistoric female statuettes—so-called Venus
figurines—often emphasised the breasts, as in the example of the Venus of
Willendorf. In historic times, goddesses such as Ishtar were shown with many breasts,
alluding to their role as protectors of childbirth and mothering. The legendary tribe of Amazons
bared their breasts, and in some accounts removed one breast to allow better combat and archery.
Some religions afford the breast a special status, either in formal teachings or in symbolism. Islam forbids public exposure of the female breasts.[12] In Christian iconography,
some works of art depict women with their breasts in their hands or on a platter, signifying that they died as a martyr by having
their breasts severed; one example of this is Saint Agatha of Sicily. In
Silappatikaram, Kannagi tears off her left breast and
flings it on Madurai, cursing it, causing a devastating fire.
In practice
Breasts are secondary sex characteristics and sexually sensitive. Bare
female breasts can elicit heightened sexual desires from men and women. Cultures that associate
the breast primarily with sex (as opposed to with breastfeeding) tend to designate bare breasts as indecent, and they are not commonly displayed in public, in contrast to male chests. Other cultures view female
toplessness as acceptable, and in some countries women have never been forbidden to bare
their chests; in some African cultures, for example, the thigh is highly sexualised and never exposed in public, but the breast
is not taboo. Opinion on the exposure of breasts often depends on the place and context, and in
some Western societies exposure of breasts on a beach may be acceptable, although in town
centres, for example, it is usually considered indecent. In some areas the prohibition against the display of a woman’s breasts
only restricts exposure of the nipples.
Women in some areas and cultures are approaching the issue of breast exposure as one of sexual
equality, since men (and pre-pubescent children) may bare their chests, but women and teenage girls are forbidden. In the
United States, the topfree equality movement seeks to
redress this imbalance. This movement won a decision in 1992 in the New York State Court of
Appeals—“People v. Santorelli”, where the court ruled that the state’s indecent exposure laws do not ban women from being
barebreasted. A similar movement succeeded in most parts of Canada in the 1990s. In
Australia and much of Europe it is acceptable for women and
teenage girls to sunbathe topless on some public beaches and swimming pools, but these are generally the only public areas where
exposing breasts is acceptable.
When breastfeeding a baby in public, legal and social rules regarding
indecent exposure and dress codes,
as well as inhibitions of the woman, tend to be relaxed. Numerous laws around the world have made public breastfeeding legal and
disallow companies from prohibiting it in the workplace. Yet the public reaction at the sight of breastfeeding can make the
situation uncomfortable for those involved.
See also modesty, nudism and exhibitionism.
Clothing
Since the breasts are flexible, their shape may be affected by clothing, and foundation
garments in particular. A brassiere (bra) may be worn to give additional support and to
alter the shape of the breasts. There is some debate over whether such support is desirable. A long term clinical study showed
that women with large breasts can suffer shoulder pain as a result of bra straps,[13] although a well fitting bra should support most of the
breasts’ weight with proper sized cups and back band rather than on the shoulders.
Plastic surgery
Plastic surgical procedures of the breast include those for both cosmetic and reconstructive surgery indications. Some
women choose these procedures as a result of the high value placed on symmetry of the human
form, and because they identify their femininity and sense of self with their breasts.
After mastectomy (the surgical removal of a breast, usually to treat breast cancer) some women undergo breast reconstruction,
either with breast implants or autologous tissue transfer, using fat and tissues from the
abdomen (TRAM flap) or back (latissiumus muscle flap).
Breast reduction surgery is a common procedure which involves removing excess breast
tissue, fat, and skin with repositioning of the nipple-areolar complex (NAC). Cosmetic procedures include breast lifts
(mastopexy), breast augmentation with implants, and
procedures that combine both elements. Implants containing either silicone gel or
saline are available for augmentation and reconstructive surgeries. Surgery can repair
inverted nipples by releasing ductal tissues which are tethering. Breast lift with or
without reduction can be part of upper body lift after massive weight loss body contouring.
Any surgery of the breast carries with it the potential for interfering with future breastfeeding,[14][15][16]
causing alterations in nipple sensation, and difficulty in interpreting mammography (xrays
of the breast). A number of studies have demonstrated a similar ability to breastfeed when breast reduction patients are compared
to control groups where the surgery was performed using a modern pedicle surgical technique.[17][18][19][20] Plastic surgery organizations have generally
discouraged elective cosmetic breast augmentation surgery for teenage girls as the volume of their breast tissue may continue to
grow significantly as they mature and because of concerns about understanding long-term risks and benefits of the
procedure.[21] Breast surgery
in teens for reduction of significantly enlarged breasts or surgery to correct hypolasia and
severe asymmetry is considered on a case by case basis by most surgeons.
Disorders
Infections and inflammations
These may be caused among others by trauma, secretory stasis/milk engorgement, hormonal stimulation, infections or autoimmune
reactions. Repeated occurrence unrelated to lactation requires endocrinological examination.
A 1930
Soviet poster.
Are you taking care of your breasts? Harden your nipples with
daily washing in cold water.
Benign conditions
Benign conditions include:
Pre-malignant diseases
- Carcinoma in situ, a pre-malignant condition which can progress to a malignant
cancer
Malignant diseases
Malignant diseases include:
See also
References
- ^ Introduction to the Human Body,
fifth ed. John Wiley & Sons, Inc.: New York, 2001. 560.
- ^ a b Anatomy of the lactating human breast redefined with ultrasound imaging, D.T.
Ramsay et al., J. Anat. 206:525-34.
- ^ www.mckinley.uiuc.edu/Handouts/female_function_dysfunction.html.
- ^ Boutros S, Kattash M, Wienfeld A, Yuksel E, Baer S,
Shenaq S. The intradermal anatomy of the inframammary fold. Plast Reconstr Surg. 1998 Sep; 102(4):1030-3. PMID
- ^ A.R. Greenbaum, T. Heslop, J. Morris and K.W.
Dunn, An investigation of the suitability of bra fit in women referred for reduction mammaplasty, Br J Plast Surg 56 (2003) (3),
pp. 230–236
- ^ C.W. Loughry, et
al (1989). "Breast volume measurement of 598 women using biostereometric analysis". Annals of Plastic Surgery
22 (5): 380 – 385.
- ^ A Woman's Body: Breasts are Not Just for Filling
Sweaters. Available online
- ^ a b c Bentley, Gillian R. (2001). "The Evolution of the Human Breast". American Journal of Physical
Anthropology 32 (38).
- ^ secondary
sex characteristics
- ^ Sir Richard Burton's English translation of Kama Sutra
- ^ Morris, Desmond (1967). The Naked Ape: a zoologist's study of the
human animal. Canada: Bantam Books, 64–68. N3924.
- ^ “They shall cover their chests” or “they should draw
their khimar (veils) over their bosoms”, depending on the translation, Quran (24:31). Available online
- ^ Ryan, EL, Pectoral girdle myalgia in women: a five-year study in a
clinical setting. Clin J Pain. 2000 Dec; 16(4):298-303.
- ^ Neifert, M; DeMarzo S, Seacat
J, Young D, Leff M, Orleans M (1990). "The influence of breast surgery, breast appearance and pregnancy-induced changes on
lactation sufficiency as measured by infant weight gain". Birth 17 (1): 31—38. PMID 2288566. Retrieved on
2007-02-11.
- ^ FAQ on Previous Breast Surgery and Breastfeeding. La Leche League International
(2006-08-29). Retrieved on 2007-02-11.
- ^ West, Diana. Breastfeeding After Breast
Surgery. Australian Breastfeeding Association. Retrieved on 2007-02-11.
- ^ Cruz-Korchin, N; Korchin L
(2004-09-15). "Breast-feeding after vertical mammaplasty with medial pedicle". Plast Reconstr Surg 15 (114):
890–94. PMID 15468394. Retrieved on 2007-02-11.
- ^ Brzozowski, D; Niessen
M, Evans HB, Hurst LN (February 2000). "Breast-feeding after inferior pedicle reduction mammaplasty". Plast Reconstr Surg
105 (2): 530–34. PMID 10697157. Retrieved on 2007-02-11.
- ^ Witte, PM; van der Lei B, van der
Biezen JJ, Spronk CA (2004-06-26). "Successful breastfeeding after reduction mammaplasty". Ned Tijdschr Geneeskd
148 (26): 1291–93. PMID 15279213. Retrieved on 2007-02-11.
- ^ Kakagia, D; Tripsiannis G,
Tsoutsos D (2005-10). "Breastfeeding after reduction mammaplasty: a comparison of 3 techniques". Ann Plast Surg 55
(4): 343–45. PMID 16186694. Retrieved on 2007-02-11.
- ^ Plastic Surgery: Policy Statements Index.
Documentary film
- Breasts, directed by Meema Spadola, 1996
External links
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