Breast

Close up of the breast of a woman. The part standing out is the nipple. The darker ring around the nipple is called Areola

Inside a breast
1 - Chest wall, 2 - Muscles on the chest, 3 - Milk-secreting glands, 4 - Nipple, 5 - Areola, 6 - Milk duct, 7 - Fat, 8 - Skin

A woman breast-feeding her child; Image done by Mary Cassatt, 1890

A breast is an important part of the female body. Mammals are named that way because the female mammals have breasts they use to feed the young. Women have a pair of breasts. In most places, breasts are private and covered with clothing, but in some places, women are allowed to show breasts in public.

Men (and male mammals) also have breasts; these breasts are built the same way than those of women; Men can't use their breast for breastfeeding though, as their breasts will usually not produce milk.

Growth and form

Breasts in young girls are flat. When they become teenagers, their breasts grow. During the teenagers growing process the breast tend to hurt around the nipple area. If the teen is small it will hurt more because the skin has to stretch and the blood has to flow to the breast.

The appearance (general form) of the breasts of a woman vary. There are different forms and sizes. The form and size of a breast are influenced by genetic factors, and the amount of fatty and connective tissue. Hormones also play a role.

Sometimes the two breasts are not equal in size, one may be larger than the other. At some point in time, the breasts may start sagging (hanging down). A study showed that this has little to do with breastfeeding. Factors that influence this are the size of the breast (before the first pregancy), the number of pregnancies, the body mass index, smoking and age.

Structure

Part of the breast is a gland. This gland makes the milk used by mothers for feeding babies. After a woman has a baby, her breasts make natural milk. When this happens it is called lactation. Feeding babies milk is called breastfeeding or nursing.

Purposes

The breasts of a woman also play a role in human sexual behaviour. They are one of most visible or obvious female secondary sex characteristics, 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 breast 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. Breasts are sensitive to touch as they have many nerve endings. 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.