Editing Breast (section)

== Structure ==
[[File:Breast anatomy normal scheme.png|thumb|upright=1.35|The breast: cross-section scheme of the [[mammary gland]]. {{ordered list |[[Chest wall]] |[[Pectoralis muscle]]s |[[Lobules]] |[[Nipple]] |[[Areola]] |[[Lactiferous duct|Milk duct]] |[[Adipose tissue|Fatty tissue]] |Skin}}]]

In women, the breasts overlie the [[pectoralis major muscle]]s and extend on average from the level of the second rib to the level of the sixth rib in the front of the [[human rib cage|rib cage]]; thus, the breasts cover much of the chest area and the chest walls. At the front of the chest, the '''breast tissue''' can extend from the [[clavicle]] (collarbone) to the middle of the [[sternum]] (breastbone). At the sides of the chest, the breast tissue can extend into the [[axilla]] (armpit), and can reach as far to the back as the [[latissimus dorsi muscle]], extending from the lower back to the [[humerus]] bone (the bone of the upper arm). As a [[mammary gland]], the breast is composed of differing layers of [[Histology|tissue]], predominantly two types: [[adipose tissue]]; and [[Lactiferous duct|glandular tissue]], which affects the lactation functions of the breasts.<ref name=GRAYS2005>{{cite book |last = Drake |first = Richard L. |title = Gray's anatomy for students |year = 2005 |publisher = Elsevier/Churchill Livingstone |location = Philadelphia |isbn = 978-0-8089-2306-0 |author2 = Vogl, Wayne |author3 = Tibbitts, Adam W.M. Mitchell |others = illustrations by Richard Richardson, Paul }}</ref>{{rp|115}} The natural [[resonant frequency]] of the human breast is about 2 [[hertz]].<ref>{{cite book |last1=Cameron |first1=John R. |last2=Skofronick |first2=James G. |last3=Grant |first3=Roderick M. |title=Physics of the Body |date=1999 |publisher=Medical Physics Publishing |location=Madison, Wis |isbn=978-0-944838-91-4 |pages=69–70 |edition=2nd |url=https://medicalphysics.org/SimpleCMS.php?content=bookpage.php&isbn=9781930524941}}</ref>

[[Morphology (biology)|Morphologically]], the breast is tear-shaped.<ref name="love_c1">{{cite book|last1=Love|first1=Susan M.|title=Dr. Susan Love's Breast Book|date=2015|publisher=Da Capo Press|location=U.S.|isbn=978-07382-1821-2|edition=6|chapter=1}}</ref> The superficial tissue layer ([[superficial fascia]]) is separated from the skin by 0.5–2.5&nbsp;cm of subcutaneous fat (adipose tissue). The [[Cooper's ligaments|suspensory Cooper's ligaments]] are fibrous-tissue prolongations that radiate from the superficial fascia to the skin envelope. The female adult breast contains 14–18 irregular lactiferous lobes that converge at the nipple. The 2.0–4.5&nbsp;mm milk ducts are immediately surrounded with dense connective tissue that support the glands. Milk exits the breast through the nipple, which is surrounded by a pigmented area of skin called the areola. The size of the areola can vary widely among women. The areola contains modified [[sebaceous gland|sweat glands]] known as [[Areolar gland|Montgomery's glands]]. These glands secrete oily fluid that lubricate and protect the nipple during breastfeeding.<ref name=stoppler>{{cite web |last1 = Stöppler |first1 = Melissa Conrad |title = Breast Anatomy |url = http://www.medicinenet.com/breast_anatomy/article.htm |access-date = 28 June 2015 |archive-url = https://web.archive.org/web/20150627065040/http://www.medicinenet.com/breast_anatomy/article.htm |archive-date = 27 June 2015 |url-status = live |df = dmy-all }}</ref> Volatile compounds in these secretions may also serve as an olfactory stimulus for the newborn's appetite.<ref>{{cite journal |doi = 10.1371/journal.pone.0007579 |title = The Secretion of Areolar (Montgomery's) Glands from Lactating Women Elicits Selective, Unconditional Responses in Neonates |year = 2009 |editor1-last = Hausberger |editor1-first = Martine |last1 = Doucet |first1 = Sébastien |last2 = Soussignan |first2 = Robert |last3 = Sagot |first3 = Paul |last4 = Schaal |first4 = Benoist |journal = PLOS ONE |volume = 4 |issue = 10 |pages = e7579 |pmid = 19851461 |pmc = 2761488 |bibcode = 2009PLoSO...4.7579D |doi-access = free }}</ref>
[[File:Areolar enlargement.png|thumb|Breasts during early pregnancy, showing enlarged [[areolar gland]]s]]
The dimensions and weight of the breast vary widely among women. A small-to-medium-sized breast weighs 500&nbsp;grams (1.1 pounds) or less, and a large breast can weigh approximately 750 to 1,000 grams (1.7 to 2.2 pounds) or more. In terms of composition, the breasts are about 80 to 90% [[stroma (tissue)|stroma]]l tissue ([[adipose tissue|fat]] and [[connective tissue]]), while [[epithelial tissue|epithelial]] or [[gland]]ular tissue only accounts for about 10 to 20% of the volume of the breasts.<ref name="pmid16728564">{{cite journal |vauthors=Lorincz AM, Sukumar S |title=Molecular links between obesity and breast cancer |journal=Endocrine-Related Cancer |volume=13 |issue=2 |pages=279–92 |year=2006 |pmid=16728564 |doi=10.1677/erc.1.00729 |quote=Adipocytes make up the bulk of the human breast, with epithelial cells accounting for only approximately 10% of human breast volume.|doi-access=free}}</ref><ref name="pmid11149569">{{cite journal |vauthors=Howard BA, Gusterson BA |title=Human breast development |journal=Journal of Mammary Gland Biology and Neoplasia |volume=5 |issue=2 |pages=119–37 |year=2000 |pmid=11149569 |doi= 10.1023/A:1026487120779|s2cid=10819224 |quote=In the stroma, there is an increase in the amount of fibrous and fatty tissue, with the adult nonlactating breast consisting of 80% or more of stroma.}}</ref><ref name="RosenfieldCookeRadovick2021">{{cite book | title = Sperling Pediatric Endocrinology | last1 = Rosenfield | first1 = Robert L. | last2 = Cooke | first2 = David W. | last3 = Radovick | first3 = Sally | chapter = Puberty in the Female and Its Disorders | date = 2021 | pages = 528–626 | publisher = Elsevier | doi = 10.1016/B978-0-323-62520-3.00016-6 | isbn = 9780323625203 | s2cid = 234131890 | chapter-url = https://books.google.com/books?id=8J7yDwAAQBAJ&pg=PA554 | quote = Estrogen stimulates the nipples to grow, mammary terminal duct branching to progress to the stage at which ductules are formed, and fatty stromal growth to increase until it constitutes about 85% of the mass of the breast. [...] Lobulation appears around menarche, when multiple blind saccular buds form by branching of the terminal ducts. These effects are due to the presence of progesterone. [...] Full alveolar development normally only occurs during pregnancy under the influence of additional progesterone and prolactin.}}</ref><ref name="pmid22206682">{{cite journal |vauthors=Hagisawa S, Shimura N, Arisaka O |title=Effect of excess estrogen on breast and external genitalia development in growth hormone deficiency |journal=Journal of Pediatric and Adolescent Gynecology |volume=25 |issue=3 |pages=e61–3 |year=2012 |pmid=22206682 |doi=10.1016/j.jpag.2011.11.005 |quote=Estrogen stimulates growth of the nipples, progression of mammary duct branching to the stage at which ductiles are formed, and fatty stromal growth until it constitutes about 85% of the mass of the breast.}}</ref><ref name="pmid2942075">{{cite journal | vauthors = Drife JO | title = Breast development in puberty | journal = Ann N Y Acad Sci | volume = 464 | issue = 1| pages = 58–65 | date = 1986 | pmid = 2942075 | doi = 10.1111/j.1749-6632.1986.tb15993.x | bibcode = 1986NYASA.464...58D | s2cid = 12735704 | url = | quote = Along with the glandular growth, there is an increase in the amount of fibrous and fatty tissue, and in fact these latter two constituents of the breast account for a far greater proportion of the morphologic growth than the proportion contributed by glandular tissue. In the nonlactating adult breast, glandular tissue accounts for no more than 20% of the breast volume, and often much less than this, and the morphologic changes at puberty are therefore mainly due to stromal expansion.}}</ref> The tissue composition ratios of the breast also vary among women. Some women's breasts have a higher proportion of glandular tissue than of adipose or [[connective tissue|connective]] tissues. The fat-to-connective-tissue ratio determines the density or firmness of the breast. During a woman's life, her breasts change size, shape, and weight due to hormonal changes during [[thelarche|puberty]], the [[menstruation|menstrual cycle]], [[Maternal physiological changes in pregnancy|pregnancy]], breastfeeding, and [[menopause]].<ref>Pamplona DC, de Abreu Alvim C. Breast Reconstruction with Expanders and Implants: a Numerical Analysis. Artificial Organs 8 (2004), pp. 353–356.</ref><ref>{{cite journal |last1 = Grassley |first1 = JS |year = 2002 |title = Breast Reduction Surgery: What every Woman Needs to Know |journal = Lifelines |volume = 6 |issue = 3 |pages = 244–249 |doi = 10.1111/j.1552-6356.2002.tb00088.x |pmid = 12078570 }}</ref>

===Glandular structure===
{{Main articles|Mammary gland}}
[[File:Normal breast histology.png|thumb|Normal [[histology]] of the breast.]]

The breast is an [[apocrine]] gland that produces the [[Breast milk|milk]] used to feed an infant. The [[nipple]] of the breast is surrounded by the [[areola]] (nipple-areola complex). The areola has many sebaceous glands, and the skin color varies from pink to dark brown. The basic units of the breast are the terminal duct lobular units (TDLUs), which produce the fatty breast milk. They give the breast its offspring-feeding functions as a mammary gland. They are distributed throughout the body of the breast. Approximately two-thirds of the lactiferous tissue is within 30&nbsp;mm of the base of the nipple. The terminal lactiferous ducts drain the milk from TDLUs into 4–18 lactiferous ducts, which drain to the nipple. The milk-glands-to-fat ratio is 2:1 in a lactating woman, and 1:1 in a non-lactating woman. In addition to the milk glands, the breast is also composed of connective tissues ([[collagen]], [[elastin]]), white fat, and the suspensory Cooper's ligaments. Sensation in the breast is provided by the [[peripheral nervous system]] innervation by means of the front (anterior) and side (lateral) cutaneous branches of the fourth-, fifth-, and sixth [[intercostal nerves]]. The T-4 nerve ([[Thoracic spinal nerve 4]]), which innervates the [[dermatomic area]], supplies sensation to the nipple-areola complex.<ref name=grabowski>{{cite book |first1 = Gerard J. |last1 = Tortora |first2 = Sandra Reynolds |last2 = Grabowski |title = Introduction to the Human Body: the Essentials of Anatomy and Physiology |date = 2001 |publisher = J. Wiley |location = New York; Toronto |isbn = 978-0-471-36777-2 |edition = Fifth. }}</ref>

===Lymphatic drainage===
Approximately 75% of the [[lymph]] from the breast travels to the axillary [[lymph node]]s on the same side of the body, while 25% of the lymph travels to the parasternal nodes (beside the sternum bone).<ref name=GRAYS2005 />{{rp|116}} A small amount of remaining lymph travels to the other breast and to the abdominal lymph nodes. The subareolar region has a lymphatic plexus known as the "subareolar plexus of Sappey".<ref name="Pacifici">{{cite web |last1=Pacifici |first1=Stefano |title=Sappey plexus {{!}} Radiology Reference Article {{!}} Radiopaedia.org |url=https://radiopaedia.org/articles/sappey-plexus-1?lang=gb |website=Radiopaedia |date=11 October 2011 |access-date=25 August 2020 |archive-date=2 May 2021 |archive-url=https://web.archive.org/web/20210502224454/https://radiopaedia.org/articles/sappey-plexus-1?lang=gb |url-status=live }}</ref> The [[axillary lymph node]]s include the pectoral (chest), subscapular (under the scapula), and humeral (humerus-bone area) lymph-node groups, which drain to the central [[axillary lymph nodes]] and to the apical axillary lymph nodes. The lymphatic drainage of the breasts is especially relevant to [[oncology]] because breast cancer is common to the mammary gland, and cancer cells can [[Metastasis|metastasize]] (break away) from a [[tumor]] and be dispersed to other parts of the body by means of the lymphatic system.

===Morphology===
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The morphologic variations in the size, shape, volume, tissue density, pectoral locale, and spacing of the breasts determine their natural shape, appearance, and position on a woman's chest. [[Breast size]] and other characteristics do not predict the fat-to-milk-gland ratio or the potential for the woman to nurse an infant. The size and the shape of the breasts are influenced by normal-life hormonal changes (thelarche, menstruation, pregnancy, menopause) and medical conditions (e.g. [[virginal breast hypertrophy]]).<ref name=wood>{{cite journal |vauthors = Wood K, Cameron M, Fitzgerald K |title = Breast Size, Bra Fit and Thoracic Pain in Young Women: A Correlational Study |journal = Chiropractic & Osteopathy |volume = 16 |page = 1 |year = 2008 |pmid = 18339205 |pmc = 2275741 |doi = 10.1186/1746-1340-16-1 |doi-access = free }}</ref> The shape of the breasts is naturally determined by the support of the suspensory Cooper's ligaments, the underlying muscle and bone structures of the chest, and by the skin envelope. The suspensory ligaments sustain the breast from the clavicle (collarbone) and the clavico-pectoral fascia (collarbone and chest) by traversing and encompassing the fat and milk-gland tissues. The breast is positioned, affixed to, and supported upon the chest wall, while its shape is established and maintained by the skin envelope.<ref>{{Cite web |title=Breast Anatomy – Breast360.org {{!}} The American Society of Breast Surgeons Foundation |url=https://breast360.org/topic/2017/01/01/breast-anatomy/ |access-date=2024-12-21 |website=breast360.org}}</ref><ref>{{Cite web |title=Breast Anatomy {{!}} SEER Training |url=https://training.seer.cancer.gov/breast/anatomy/ |access-date=2024-12-21 |website=training.seer.cancer.gov}}</ref> In most women, one breast is slightly larger than the other.<ref name=love_c1/> More obvious and persistent asymmetry in breast size occurs in up to 25% of women.<ref name=mgh2010>{{cite web |url = http://www.mgh.harvard.edu/children/adolescenthealth/articles/aa_breast_development.aspx |title = Breast Development |publisher = Massachusetts Hospital for Children |access-date = 2 June 2010 |archive-url = https://web.archive.org/web/20101225165742/http://www.mgh.harvard.edu/children/adolescenthealth/articles/aa_breast_development.aspx |archive-date = 25 December 2010 |url-status = dead |df = dmy }}</ref>

The base of each breast is attached to the chest by the deep fascia over the pectoralis major muscles. The base of the breast is semi-circular, however the shape and position of the breast above the surface is variable.<ref>{{Citation |last=Gould |first=Stanley F. |title=Anatomy of the Breast |date=1983 |work=Lactation: Physiology, Nutrition, and Breast-Feeding |pages=23–47 |editor-last=Neville |editor-first=Margaret C. |url=https://link.springer.com/chapter/10.1007/978-1-4613-3688-4_2 |access-date=2024-12-25 |place=Boston, MA |publisher=Springer US |language=en |doi=10.1007/978-1-4613-3688-4_2 |isbn=978-1-4613-3688-4 |editor2-last=Neifert |editor2-first=Marianne R.|url-access=subscription }}</ref> The space between the breast and the pectoralis major muscle, called [[retromammary space]], gives mobility to the breast. The chest ([[thoracic cavity]]) progressively slopes outwards from the thoracic inlet (atop the [[Human breastbone|breastbone]]) and above to the lowest ribs that support the breasts. The inframammary fold (IMF), where the lower portion of the breast meets the chest, is an anatomic feature created by the adherence of the breast skin and the underlying connective tissues of the chest; the IMF is the lower-most extent of the anatomic breast. Normal breast tissue has a texture that feels nodular or granular, with considerable variation from woman to woman.<ref name="love_c1" />

Breasts have been categorized into four general morphological groups:  "flat, spheric, protruded, and drooped", or "small/flat, large/inward, upward, and droopy".<ref>{{Cite journal |last1=Suh |first1=Minyoung |last2=Park |first2=Jung Hyun |date=2022-01-01 |title=Breast Geometry Characterization of Young American Females Using 3D Image Analysis |journal=Applied Sciences |language=en |volume=12 |issue=17 |pages=8578 |doi=10.3390/app12178578 |doi-access=free |issn=2076-3417}}</ref><ref>{{Cite journal |title=Brassiere Pattern Development Based on 3D Measurements of Upper Body Types for Women in Their 30's |url=https://koreascience.kr/article/JAKO200827464608269.page |journal=The Research Journal of the Costume Culture|date=2008 |volume=16 |issue=3 |last1=Mi-Sook |first1=Cho }}</ref><ref>{{Cite journal |last1=Coltman |first1=Celeste E. |last2=Steele |first2=Julie R. |last3=McGhee |first3=Deirdre E. |date=2018-09-02 |title=Effects of age and body mass index on breast characteristics: a cluster analysis |url=https://www.tandfonline.com/doi/abs/10.1080/00140139.2018.1481229 |journal=Celeste E. Coltman |volume=61 |issue=9 |pages=1232–1245 |doi=10.1080/00140139.2018.1481229 |pmid=29792567 |issn=0014-0139|url-access=subscription }}</ref>

==== Support ====
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While it is a common belief that breastfeeding causes [[Ptosis (breasts)|breasts to sag]],<ref name="lauersen">{{cite book |last = Lauersen |first = Niels H. |title = The Complete Book of Breast Care |year = 1998 |publisher = Fawcett Columbine/Ballantine |location = New York |isbn = 978-0-449-91241-6 |edition = 1st Trade Paperback |author2 = Stukane, Eileen |quote = ...there is no medical reason to wear a bra, so the decision is yours, based on your own personal comfort and aesthetics. Whether you have always worn a bra or always gone braless, age and breastfeeding will naturally cause your breasts to sag. |url = https://archive.org/details/completebookofbr00laue_0 }}</ref> researchers have found that a woman's breasts sag due to four key factors: cigarette smoking, [[gravidity|number of pregnancies]], [[gravity]], and weight loss or gain.<ref name="thompson">{{cite journal |doi = 10.1016/j.asj.2008.07.004 |title = The Effect of Breastfeeding on Breast Aesthetics |year = 2008 |last1 = Rinker |first1 = B |last2 = Veneracion |first2 = M |last3 = Walsh |first3 = C |journal = Aesthetic Surgery Journal |volume = 28 |issue = 5 |pages = 534–7 |pmid = 19083576 |doi-access = free}}
*{{cite news |author=Andrea Thompson |date=2 November 2007 |title=Breastfeeding Does Not Make Breasts Sag, Study Suggests |work=LiveScience |url = http://www.livescience.com/1998-breastfeeding-breasts-sag-study-suggests.html |access-date = 9 May 2015 |archive-url = https://web.archive.org/web/20120703153917/http://www.livescience.com/1998-breastfeeding-breasts-sag-study-suggests.html |archive-date = 3 July 2012 |url-status = live}}</ref> Women sometimes wear bras because they mistakenly believe they prevent breasts from sagging as they get older.<ref name="burn" /> Physicians, lingerie retailers, teenagers, and adult women used to believe that bras were medically required to support breasts. In a 1952 article in ''Parents' Magazine'', Frank H. Crowell erroneously reported that it was important for teen girls to begin wearing bras early. According to Crowell, this would prevent sagging breasts, stretched blood vessels, and poor circulation later on.<ref name="brumberg">{{cite book |url=http://course1.winona.msus.edu/pjohnson/e111/e111f99/brumberg.htm|archive-url=https://web.archive.org/web/20020328155254/http://course1.winona.msus.edu/pjohnson/e111/e111f99/brumberg.htm |isbn=0-679-73529-1 |page=336|title=The Body Project: An Intimate History of American Girls|archive-date=28 March 2002|first=Joan Jacobs |last=Brumberg|year=1998 |publisher=Knopf Doubleday Publishing }}</ref> This belief was based on the false idea that breasts cannot anatomically support themselves.<ref name="burn">{{cite web |title=Don't burn your bra just yet |url=https://www.independent.co.uk/life-style/health-and-families/health-news/dont-burn-your-bra-just-yet-622008.html |website=The Independent |date=22 September 2011 |access-date=8 October 2018 |archive-url=https://web.archive.org/web/20180717232012/https://www.independent.co.uk/life-style/health-and-families/health-news/dont-burn-your-bra-just-yet-622008.html |archive-date=17 July 2018 |url-status=live}}</ref><ref name="007b Breast">{{cite web |url=http://www.007b.com/why_wear_bras.php |title=Female Intelligence Agency: Why Do Women Wear Bras? |publisher=007b Breast |access-date=10 May 2011 |archive-url=https://web.archive.org/web/20110831044824/http://www.007b.com/why_wear_bras.php |archive-date=31 August 2011 |url-status=live}}</ref>

[[Sports bra]]s are sometimes used for cardiovascular exercise, sports bras are designed to secure the breasts closely to the body to prevent movement during high-motion activity such as running. Studies have indicated sports bras which are overly tight may restrict respiratory function.<ref>{{Cite journal |last1=Ocran |first1=Francisca Margarita |last2=Ji |first2=Xiaofen |last3=Zhai |first3=Lina |date=January 2022 |title=A study to evaluate pressure distribution of different sports bras |journal=Journal of Engineered Fibers and Fabrics |language=en |volume=17 |doi=10.1177/15589250221118643 |issn=1558-9250|doi-access=free }}</ref><ref>{{Cite journal |last1=Kipp |first1=Shalaya |last2=Leahy |first2=Michael G. |last3=Sheel |first3=A. William |date=2024-06-01 |title=Sports Bra Restriction on Respiratory Mechanics during Exercise |url=https://pubmed.ncbi.nlm.nih.gov/38350462/ |journal=Medicine and Science in Sports and Exercise |volume=56 |issue=6 |pages=1168–1176 |doi=10.1249/MSS.0000000000003403 |issn=1530-0315 |pmid=38350462}}</ref>