The breast sits on the chest (pectoral) muscles which cover the ribs.
The female breast extends from just below the collarbone (clavicle) to the armpit and across to the breastbone (sternum) in the centre of the chest. Both men and women have breasts, but women have significantly more breast (glandular) tissue than men.
Boys and girls have similar breast tissue in childhood, but during puberty high testosterone and low oestrogen levels prevent further breast development in boys.
Girls will often feel a firm, tender "breast bud" behind their nipples as the glandular tissue begins to develop under the influence of hormones produced by the ovaries and pituitary gland.
Mature female breasts
Mature female breasts are made up of:
- Fatty tissue
- Fibrous connective tissue and ligaments which provide support for the breast
- 15-20 lobes which, like bunches of grapes, are divided into smaller lobules - these are the milk-producing glands
- Ducts which transport the milk to the nipple
The darker skin surrounding the nipple is called the areola. Sweat glands contained in the areola moisturise the skin to assist with breastfeeding.
Prior to menopause, breasts have more glandular tissue than fatty tissue. This means that pre-menopausal women have a higher breast density. It is more difficult to read a mammogram when the breast tissue is very dense, making screening mammograms less reliable in young women.
After menopause (when periods have stopped as the ovaries cease producing oestrogen) the amount of glandular tissue decreases and the remaining tissue shrinks, so that there's a greater proportion of fatty tissue, and a lower breast density. Breast density remains higher in women taking hormone replacement therapy (HRT), so mammograms may also be less accurate in these women.