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Breast Anatomy (cont.)

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What happens to the breasts in pregnancy?

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During pregnancy, the breasts grow further due to stimulation by estrogens (female hormones). The growth during pregnancy is more uniform than that observed at puberty. The amount of tissue capable of producing milk is approximately the same in all women, so women with smaller breasts produce the same amount of milk as women with larger breasts. During pregnancy, the areola becomes darker and enlarges in size.

How does breast tissue develop?

Breast tissue begins to form in the fourth week of fetal life. In the fetus, breast tissue develops along two "milk lines" that start at the armpit and extend to the groin. Uncommonly, an extra (ancillary) breast can develop along this line. On the skin surface, an extra nipple (supernumerary nipple) may develop along this line.

Picture of the milk lines
Picture of the milk lines

How are human breasts different from other species?

In other primates (such as apes), the breasts develop only when they are producing milk. After the young have been weaned, the breasts flatten again. In humans, the breasts enlarge at puberty and stay enlarged throughout a woman's life.

What are the most common medical conditions affecting the breasts?

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Breast health is a source of concern for most women. Although breast cancer is a fairly common malignancy affecting one out of every eight women in the U.S. at some point in life, benign (non-cancerous) conditions of the breast are much more common. In fact, most masses and lumps in the breasts are not cancer. Breast cancer occurs in males as well, but it accounts for a small percentage of all breast cancers.

Among the benign breast conditions, cysts and fibrocystic changes are common. One type of benign tumor in particular, known as a fibroadenoma, is common in young women. Infections of the breast tissue can also occur, particularly during breastfeeding. Mastitis is the medical term for inflammation of the breast.

Medically reviewed by a Board-Certified Family Practice Physician

REFERENCE: MedscapeReference.com. Breast Anatomy.

Medically Reviewed by a Doctor on 6/30/2015

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Breast Anatomy - Pregnancy Question: What changes did you experience with your breasts during pregnancy and while breastfeeding?
Breast Anatomy - Medical Conditions Question: What medical conditions have you experienced that involve your breasts?
Breast Anatomy - Gynecomastia Question: Please describe your experience with gynecomastia.