Mammary glands or mammae, are organs which, in female mammals, are developed to secrete milk for feeding young. The presence of mammae is characteristic of mammals, which literally means "animals with mammaries." In humans, they are located on the breast, i.e. the upper anterior part of the chest, and are individually called breasts. In other mammals, the location and number varies with the species.
In medical and zoological parlance, both female and male mammals have breasts, but those in females develop and enlarge in size at adulthood while those of males remain rudimentary. Histologically and developmentally, mammary glands are modified sweat glands.
In the United States, during the middle of the twentieth century, there was a tendency to deemphasize breastfeeding infants in favor of using bottled formula, partly from an impression that bottles were more modern, scientific, or hygienic. During the latter part of that century, breastfeeding has returned to favor, partly as a result of medical studies showing although infant formula is nutritionally sound, nevertheless breastfeeding has health benefits for both mother and infant. For example, one medical-school-sponsored website states that in the mother breastfeeding promotes faster recovery from childbirth, feelings of well-being, and lower risk of osteoporosis, and, in the infant, fewer infections and medical problems, better brain development, and higher oxygenation. The American Academy of Pediatrics and other organizations recommend exclusive breastfeeding for the first six months of life 
Breastfeeding is one of a number of factors that lead to emotional bonding between mother and child.
In the United States, promoters of breastfeeding seek greater social acceptance of public breast exposure when it occurs in the context of breastfeeding; although, they say, a woman's right to breastfeed in public is protected by law in many states, some people "may consciously or unconsciously confuse it with something that's sexual and should be done in privacy."
Diseases of the Breast
Diseases of the breasts include mastitis, cysts and breast cancer. Regular Breast Examinations are recommended for women. Additionally, many breasts are, or can be at times, extremely sensitive to pain and discomfort, and are highly susceptible to bruising.
Custom, Taboo, and Nudity
The size of breasts are a conspicuous physical difference between men and women, and as such have an association with sexuality. Attitudes toward their public exposure vary with time and place. In the United States, they almost define the borderline of what is permissible to show in public; in general, exposure of a woman's nipples is taboo (and illegal) except in the context of breastfeeding. Clothing that fits tightly around the neck and de-emphasizes the separation and softness of the breasts is considered modest or conservative, clothing that does the opposite is considered "daring."
The Bible mentions breasts both in connection with infant feeding, e.g. Psalms 23:9 "But thou art he that took me out of the womb: thou didst make me hope when I was upon my mother's breasts," and sensuality, in the Song of Solomon.
Breasts in Christianity
- Bhatnagar, S. M. (2000), Essentials of Human Embryology, p. 223, "The Integumentary System:" "The mammary glands are regarded as modified sweat glands and hence are described here."
- Benefits Of Breast-Feeding, Intelihealth (Harvard Medical School's health website)
- Breastfeeding and the Use of Human Milk, American Academy of Pediatrics; notes that exclusive breastfeeding for the first 6 months of life is also recommended by the American College of Obstetricians and Gynecologists, American Academy of Family Physicians, Academy of Breastfeeding Medicine, World Health Organization, United Nations Children's Fund
- Breastfeeding in Public, La Leche League