The breasts are divided by an invisible line running up and down and right to left through the nipple. Each of these 4 regions is called a quadrant. Most breast cancers develop in the upper outer quadrant of the breast, closest to the armpit. This is because this area has a lot of glandular tissue.
Each breast lies over a large muscle (called the pectoralis major muscle) on the chest. The breast covers a fairly large area. It goes from just below the collarbone (called the clavicle) to the armpit (called the axilla) and across to the breastbone (called the sternum).
Breast development in women @(Model.HeadingTag)>
Breasts start to grow during puberty, which usually takes place between 10 and 12 years of age. At this time, the breasts respond to hormonal changes in the body. These changes include higher estrogen and progesterone levels in the body. The breasts start to build up fat and the ducts begin to grow and branch. The glands of the breast also start to develop during puberty. The breast skin stretches as the breasts grow, creating a rounded appearance.
Young women tend to have denser breasts with more gland tissue than older women. As a woman ages, much of the gland and duct tissues are replaced with fat. This makes the breasts less dense. Ligaments also lose their elasticity as a woman ages, which causes the breasts to change shape and lose some of their fullness.
Women’s breasts vary in size and shape. The size depends on the amount of fat in the breast. A woman’s breasts are rarely the same size. One breast is usually slightly larger or smaller, higher or lower or shaped differently than the other.
Breast changes during menstruation and menopause @(Model.HeadingTag)>
Estrogen and progesterone cause changes to the breast tissues each menstrual cycle. In the first part of the menstrual cycle, estrogen stimulates the milk ducts to make them grow. Progesterone takes over in the second part of a woman’s menstrual cycle. It stimulates the glands in the lobules so they are ready to make milk if a woman becomes pregnant.
After menopause, the ovaries don’t make estrogen and progesterone so breasts don’t go through these monthly changes.
Breast changes during pregnancy and lactation @(Model.HeadingTag)>
The main function of a woman’s breasts is to make, store and release milk to feed a baby. After giving birth, hormones in a woman’s body stimulate the glands in the lobules throughout the breast to make milk. The ducts carry the milk to the nipple. Milk passes from the nipple to the baby during breast-feeding.
The breasts of women who aren’t pregnant or breast-feeding contain mostly fat and ducts. There is a small amount of gland tissue, but the breast glands don’t develop fully until the 6th month of pregnancy in most women.
The breasts of pregnant and breast-feeding women contain mostly gland tissue that makes milk. This is why a woman’s breasts tend to get bigger during pregnancy and when a woman is breast-feeding.
Hormones and the breast @(Model.HeadingTag)>
Estrogen is the main female hormone. It influences female sexual characteristics, such as breast development, and it is necessary for reproduction. Most of the estrogen in a woman’s body is made by the ovaries, but a small amount is made by the adrenal glands.
Progesterone is the other female sex hormone made in the ovaries. Its role is to prepare the uterus, or womb, for pregnancy during each menstrual cycle. Progesterone also plays a role in completing the development of the mammary glands during pregnancy so they can make milk after childbirth.