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
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.
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 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.
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 and thus become less likely to become a victim of
rape.
Changes
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
Main articles: 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 female
secondary sex characteristics, 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
[9].
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.
[10]
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.
[11] 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 is often dependent 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 indecent. In some areas, the prohibition against the display of a woman’s breasts generally 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. Santorelliâ€, 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,
[12] 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,
[13][14][15] 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.
[16][17][18][19] 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.
[20] 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.''
★
Mastitis
★
★ bacterial mastitis
★
★ mastitis from milk engorgement or secretory
stasis
★
★ mastitis of
mumps
★
★ chronic intramammary
abscess
★
★ chronic subareolar
abscess
★
★
tuberculosis of the breast
★
★
syphilis of the breast
★
★ retromammary
abscess
★
★
actinomycosis of the breast
★
★
Mondor’s disease
★
★
duct ectasia syndrome
★
★
breast engorgement
===
Benign conditions===
★
Congenital disorders
★
★
inverted nipple
★
★
supernumerary nipples/
supernumerary breasts (polymazia / polymastia) /duplicated nipples
★
Aberrations of normal development and involution
★
★ cyclical nodularity
★
★
cysts
★
★
fibroadenoma -
benign tumor
★
★
gynecomastia (males)
★
★
nipple discharge,
galactorrhea
★
★ mammary
fistula
★
Fibrocystic disease / Fibrocystic changes
★
★ cysts
★
★
epithelial hyperplasia
★
★
epithelial metaplasia
★
★
papillomas
★
★
adenosis
★
Pregnancy-related
★
★
galactocoele
===
Malignant diseases===
★
Breast cancer (mammary
carcinoma)
★
Carcinoma in situ
★ Paget’s disease of the nipple, also known as
Paget’s disease of the breast
References
1. ''Introduction to the Human Body, fifth ed.'' John Wiley & Sons, Inc.: New York, 2001. '560'.
2. Anatomy of the lactating human breast redefined with ultrasound imaging, D.T. Ramsay et al., ''J. Anat.'' '206':525-34.
3. www.mckinley.uiuc.edu/Handouts/female_function_dysfunction.html
4. 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
5. 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
6. Breast volume measurement of 598 women using biostereometric analysis, C.W. Loughry, ''et al'', , , Annals of Plastic Surgery, 1989
7. A Woman's Body: Breasts are Not Just for Filling Sweaters. Available online
8. The Evolution of the Human Breast, , Gillian R., Bentley, American Journal of Physical Anthropology, 2001
9. Sir Richard Burton's English translation of Kama Sutra
10. The Naked Ape: a zoologist's study of the human animal, , Desmond, Morris, Bantam Books, , N3924
11. “They shall cover their chests†or “they should draw their khimar (veils) over their bosomsâ€, depending on the translation, Quran (24:31). Available online
12. Ryan, EL, Pectoral girdle myalgia in women: a five-year study in a clinical setting. Clin J Pain. 2000 Dec; 16(4):298-303.
13. The influence of breast surgery, breast appearance and pregnancy-induced changes on lactation sufficiency as measured by infant weight gain, , M, Neifert, Birth,
14. FAQ on Previous Breast Surgery and Breastfeeding
15. Breastfeeding After Breast Surgery
16. Breast-feeding after vertical mammaplasty with medial pedicle, , N, Cruz-Korchin, Plast Reconstr Surg,
17. Breast-feeding after inferior pedicle reduction mammaplasty, , D, Brzozowski, Plast Reconstr Surg,
18. Successful breastfeeding after reduction mammaplasty, , PM, Witte, Ned Tijdschr Geneeskd,
19. Breastfeeding after reduction mammaplasty: a comparison of 3 techniques, , D, Kakagia, Ann Plast Surg,
20. Plastic Surgery: Policy Statements Index.
Documentary film
★ ''Breasts'', directed by Meema Spadola, 1996
See also
★
Breast bondage
★
Breast fetishism
★
Breast self-examination
★
Intimate part
★
Mammary intercourse
★
Teat
★
Milk line
★
Wonderbra
External links
★
Images of female breasts
★
Pregnancy and your breasts
★
Stages of breast development, from Puberty101
★
“Are Women Evolutionary Sex Objects?: Why Women Have Breastsâ€
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