Breast
The term breast, also known by the Latin mamma in human anatomy, refers to the upper ventral region of an animal's torso, particularly that of mammals, including human beings. Furthermore, the breasts are parts of a mammal's body which contain the organs that secrete milk used to feed infants. Males also have breasts and are born with the main milk ducts intact, but while the gland that produces milk is present in the male, it normally remains undeveloped. In some situations male breast development does occur, a condition called gynecomastia. Milk production can also occur in both men and women as a rare side-effect of some medicinal drugs (such as some antipsychotic medication). Both sexes have a large concentration of blood vessels and nerves in their nipples.
Anatomy
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A woman's 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 in an 'axillary tail'. 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.
Important parts of the breasts include mammary glands, the axillary tail (tumours can occur here), the lobules, Cooper's ligaments, the areola and the nipple. The nipple is supplied by the T4 dermatome.
During puberty, sex hormones, chiefly estrogen, cause the development of a woman's breasts. This hormone has been demonstrated to cause the development of woman-like, enlarged breasts in men.
As breasts are mostly composed of adipose tissue, their size can change over time if the woman gains or loses weight. It is typical for them to grow in size during pregnancy, mainly due to hypertrophy of the exocrine gland in response to the hormone prolactin.
Their blood supply is derived from the internal thoracic artery (previously referred to as the internal mammary artery) and long thoracic artery (previously referred to as the external mammary artery).
Lymphatic drainage
As breast cancer is a common cancer, the lymphatic drainage of the breast (sites where cancer may metastasize) is important.
About 75% of lymph from the breast travels to the ipsilateral (same side) 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.
Function
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A common misconception is that human female breasts are shaped the way that they are so that they can feed babies by producing milk. The mammary glands that secrete the milk from the breasts make up a relatively small fraction of the overall breast tissue. Most of the human female breast is actually adipose tissue (fat) and connective tissue. Breast size does not make any difference to a woman's ability to nurse a baby. Zoologists point out that no other female mammal has breasts of comparable size when not lactating.
It is commonly assumed by biologists that the real evolutionary purpose of women having breasts is to attract the male of the species; that, in other words, breasts are secondary sex characteristics. Some biologists (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 typical piggy-back position, humans are more likely to successfully copulate mating face on. 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 would have helped foundate a relationship between partners beyond merely a sexual one.
Others believe that the human breast evolved in order to prevent infants from suffocating while feeding. Since human infants do not have a protruding jaw like our ancestors and the other primates, the infant's nose might be blocked by a flat female chest while feeding. According to this theory, as the human jaw became recessed, so the breasts became larger to compensate.
Because some cultures place a high value on symmetry of the female human form, and because women often identify their femininity and sense of self with their breasts, many women in developed countries undergo breast reconstruction after mastectomy for breast cancer.
Size and shape
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There is naturally a great variety in the size and shape of breasts in women (and men), with size being affected by various factors including race, weight, eating habits and exercise. The size of a woman's breasts is typically expressed as a 'bra size'. According to the results of the 'Size UK' survey, the average bra size in the UK has increased from a 34B in the 1950s to a 36C today, and the average size for US women is a 34B as of 2005 by the CDC. Many women suffer from insecurity about their breasts, and in some cultures it is not uncommon for women who are unhappy with their size to seek surgery either to artificially reduce or enlarge their breasts.
Women with exceptionally large breasts may experience back pain, whilst in some Western societies there is a belief amongst some that small breasts make a woman less sexually attractive. There is no relationship between breast size and ability to breastfeed.
A 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 during puberty, 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 during puberty.
It is typical for a woman's breasts to be unequal in size (statistically it is slightly more common for the left breast to be the larger), particularly whilst the breasts are developing during puberty. In some rare cases, one breast may be greatly larger or smaller than the other, or fail to develop entirely.
Terminology
A brassiere (from French, lit: arm-holder) or bra is an item of women's underwear consisting of two cups that totally or partially cover the breasts for support and modesty.
Being topless is the state of having bare breasts. For more on modesty regarding breasts, see Nudity.
There are many slang terms for the breasts. The terms tits, boobs, boobies, cans, rack, hooters, knockers, headlights, twins, melons and jugs are commonly employed, though are generally considered derogatory or vulgar.
Cultural status
Some studies have shown that bare breasts can elicit heightened sexual desires from men and women.
Because the breasts are sexually sensitive in many cases, many cultures view them as private or 'dirty', or interpret their display as sexual (in some cases, even when they are being used for their primary purpose of nursing offspring). Sometimes, this has led to women being arrested for indecent exposure for breastfeeding their children in public. Opinions differ as to whether this sexual response on the part of others is the result of breasts, in general, being covered or uncovered. In addition to the above references, see also nudism.
In a different sort of response, women in some areas and cultures are approaching the issue as one of equality: men may bare their chests, but women are forbidden. In the United States, the Topfree equality movement seeks to redress this imbalance; this movement has won a decision in 1992 in a New York Court of Appeals which seems to substantially support their assertions. A similar movement succeeded in most parts of Canada in the 1990s, and in some countries women have never been forbidden to bare their chests.
Historically, breasts were regarded as fertility symbols, due to their association with life-giving milk. Ancient statues of goddesses—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 multiple breasts, alluding to their role as goddesses of childbirth.
Disorders of the breasts
Infections and inflammations
- Other infections
- Inflammations
Benign breast disease
- Aberrations of normal development and involution
- fibroadenomatosis
- cyclical nodularity
- cysts
- fibroadenoma - benign tumor
- Pregnancy-related
Malignant breast disease
- breast cancer (mammary carcinoma)
- carcinoma in situ
- Paget's disease of the nipple or Paget's disease of the breast
See also
- breastfeeding
- breast fetishism
- breast implant
- breast reconstruction
- gynecomastia
- intimate parts
- topfree equality
- mammary intercourse
- puberty