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Breast

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Breast
Morphology of human female breasts with the areola, nipple, and inframammary fold
Human male breasts with defined pectoral muscles
Details
ArteryInternal thoracic artery
VeinInternal thoracic vein
Identifiers
Latinmamma (mammalis 'of the breast')[1]
Anatomical terminology

The breast is an organ on the mid to upper chest area. It is just below the shoulders near the center of the upper chest region of humans and other primates. Humans have two breasts. Both boys and girls have breasts at birthave glands that produce milk. Breastfeeding is when a mother feeds her baby with milk from her breasts.

Men also have breasts. They are built the same way as those of women, but are usually smaller, Men cannot use their breasts for breastfeeding. Their breasts will usually not produce milk, but might become larger and produce milk during some diseases or with some hormonal medical treatments.[2]

Growth and form

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Girls develop breasts during puberty due to sex hormones, mainly estrogen.

The appearance and size of the breasts of a woman may vary due to genetic factors, and the amount of fatty and connective tissue.[3] Hormones also play a role.[4]

Estrogen promotes the growth of mammary glands and ducts, while progesterone induces milk-producing cells to develop. Prolactin and oxytocin stimulate milk production. Oxytocin also causes milk to be spurted from a lactating breast.[5]

The two breasts usually are not equal in size — one may be larger than the other, but this is common.[6]

During menopause, as levels of estrogen decrease, tissue in the breasts reduce as well, and the breasts may start sagging.[4] A study showed that breastfeeding does not cause sagging. Factors that do influence sagging are the size of the breast (before the first pregnancy), number of pregnancies, body mass index, smoking, age and certain physical disorders.[7]

Structure

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The breast: cross-section scheme of the mammary gland.

The center of the breast is the nipple. The areola is a circular area around the nipple. The breast contains mammary glands. Each breast has 15 to 20 milk ducts.[8] Ducts carry the milk produced by these glands to the nipples. After a woman has a baby, her breasts undergo lactation — the production of natural milk.

Feeding babies milk is called breastfeeding or nursing.[9]

While it is a common belief that breastfeeding causes breasts to sag,[10] researchers have found that a woman's breasts sag due to four key factors: cigarette smoking, number of pregnancies, gravity, and weight loss or gain.[11]

Sports bras 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.[12]

Purposes

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woman breastfeeding her child

The breasts of a woman also play a role in human sexual behavior. They are one of the most visible or obvious female secondary sex characteristics.[13] They play an important role in sexual attraction of partners. They can also give pleasure to the individual. When sexually stimulated, the size of the breasts increases, venous patterns across the breasts become more visible, and nipples grow harder. During sexual intercourse, it is common practice to press or massage breasts with hands. Breast Tickling sometimes also happens and is done by placing your hands underneath her breasts and tickling upwards. Breast Tickling can also be done on the top, the sides and her nipples.

Breasts are sensitive to touch as they have many nerve endings.[14] 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.[15]

Breastfeeding

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The primary function of the breasts, as mammary glands, is the nourishing of an infant with breast milk. Milk is produced in milk-secreting cells in the alveoli. When the breasts are stimulated by the suckling of her baby, the mother's brain secretes oxytocin. High levels of oxytocin trigger the contraction of muscle cells surrounding the alveoli, causing milk to flow along the ducts that connect the alveoli to the nipple.[16]

Full-term newborns have an instinct and a need to suck on a nipple, and breastfed babies nurse for both nutrition and for comfort.[17] Breast milk provides all necessary nutrients for the first six months of life, and then remains an important source of nutrition, alongside solid foods, until at least one or two years of age.[18]

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References

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  1. ↑ "mammal". Dictionary.reference.com. Archived from the original on 14 November 2011. Retrieved 31 October 2011.
  2. ↑ Introduction to the Human Body, fifth ed. John Wiley & Sons, Inc.: New York, 2001. 560.
  3. ↑ "Size and Shape". afraidtoask.com. Archived from the original on 28 July 2010. Retrieved 30 July 2010.
  4. 1 2 "Normal Breast Development". The Ohio State University Medical Center. Archived from the original on 21 July 2010. Retrieved 30 July 2010.
  5. ↑ Perez, Jane. "Breast Anatomy & Physiology — Lactation". Herballove.com. Retrieved 30 July 2010.[permanent dead link]
  6. ↑ Jelovsek, Frederick R. "Breast Asymmetry - When Does It Need Treatment?". wdxcyber.com. Archived from the original on 3 July 2012. Retrieved 30 July 2010.
  7. ↑ "Breastfeeding Does Not Create Sagging Breasts; Study Throws Out Old Wives' Tale". Archived from the original on 3 May 2008.
  8. ↑ Sajadi-Ernazarova, K. R.; Sugumar, K.; Adigun, R. (16 October 2017). "Breast Nipple Discharge". Sajadi-Ernazarova KR, Adigun R. Breast, Nipple Discharge. National Center for Biotechnology Information, U.S. National Library of Medicine. PMID 28613688.
  9. ↑ "Breast Anatomy". Healthcommunities.com. Archived from the original on 29 March 2010. Retrieved 30 July 2010.
  10. ↑ Niels H Lauersen (1998). The complete book of breast care. Internet Archive. Fawcett Columbine/Ballantine. ISBN 978-0-449-91241-6.
  11. ↑ "Don't burn your bra just yet". The Independent. 2000-11-02. Retrieved 2026-07-15.
  12. ↑ Price, Penny (2025-08-12). "The Perfect Nursing Bra for Busty Moms". Penniless Parenting. Retrieved 2026-07-15.
  13. ↑ "secondary sex characteristics". Archived from the original on 2013-05-16. Retrieved 2008-03-06.
  14. ↑ "The entire breast is a network of nerve endings" link Archived 2009-03-03 at the Wayback Machine
  15. ↑ Sir Richard Burton's English translation of Kama Sutra
  16. ↑ "The physiological basis of breastfeeding", Infant and Young Child Feeding: Model Chapter for Textbooks for Medical Students and Allied Health Professionals, World Health Organization, 2009, retrieved 2026-07-15
  17. ↑ Lawrence 2016, p. 201.
  18. ↑ Lawrence, Ruth (2016) (2016). Breastfeeding: a guidefor the medical profession 8th edition. Philadelphia. pp. 201. ISBN 978-0-323-35776-0.{{cite book}}: CS1 maint: numeric names: authors list (link)

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