Breast
(Anatomy and Function)

Breast Summary
The breast generally refers to the chest, however, more specifically, to the mammary gland. The mammary gland is a milk producing gland comprised largely of fat. Within the mammary gland is a complex network of branching ducts. The ducts exit from sac-like structures called lobules, which can produce milk in females. The darkened area around the nipple is called the areola. Common medical concerns in regard to the breast include breast lumps, breast cysts, breast cancer, and breast infections.
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What is the breast?

The breast generally refers to the front of the chest and medically specifically to the mammary gland.

(The word "mammary" comes from "mamma," the Greek and Latin word for the breast, which derives from the cry "mama" uttered by infants and young children, sometimes meaning "I want to feed at the breast.")

How is the mammary gland designed?

The mammary gland is a milk-producing structure that is composed largely of fat cells (cells capable of storing fat). The fat deposits are laid down in the breast under the influence of the female hormone estrogen. Just as the surge of estrogens at adolescence encourages this process, androgens, such as testosterone, discourage it.

Within the mammary gland there is a complex network of branching ducts (tubes or channels). These ducts exit from sac-like structures called lobules.

The lobules in the breast are the glands that can produce milk in females when they receive the appropriate hormonal stimulation.

The breast ducts transport milk from the lobules out to the nipple. The milk exits the ducts from the breast at the nipple.

Picture of the anatomy of the breast
Picture of the anatomy of the breast

How are human breasts different from those of other primates?

Human breasts function somewhat differently than those of other primates. In other primates, the breasts grow only when the female is producing milk (lactating). When the non-human primate female has weaned her young, her breasts flatten back down. In humans, the breasts develop at adolescence usually well before any pregnancy has occurred and the breasts stay enlarged throughout the remainder of life.

What happens to the breasts in pregnancy?

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During pregnancy the breasts grow further. This growth is much more uniform than that at adolescence. The breasts of women with small breasts tend to grow about as much during pregnancy as those of women with large breasts. The amount of milk-producing tissue is essentially the same. This is the reason that when milk production begins, small-breasted women produce as much milk as do large-breasted women.

Medically Reviewed by a Doctor on 9/18/2012

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Breast - Changes in Pregnancy Question: In what ways did your breasts change during pregnancy?
Breast - Changes in Appearance Question: How have your breasts changed physically during different phases of your life?
Breast - Changes in Nipples Question: Describe the changes in your nipples during pregnancy and while breastfeeding.