There is no perfect shape or size for breasts. Normal breasts can be large or small, smooth or lumpy, and light or dark. Your breasts start growing when you begin puberty. During puberty the hormone levels in your body change, which causes your breasts to develop and your periods to start.
Breast development happens in certain stages during a woman's life: first before birth, again at puberty, and later during the childbearing years. This starts with a thickening in the chest area called the mammary ridge or milk line. By the time a baby girl is born, nipples and the beginnings of the milk-duct system have formed. The first thing to develop are lobes, or small subdivisions of breast tissue. Mammary glands develop next and consist of 15 to 24 lobes. Mammary glands are influenced by hormones activated in puberty. Shrinkage involution of the milk ducts is the final major change that happens in the breast tissue.
The breasts are specialised organs, which are located on the anterior chest wall. The female breast is more developed than the male breast, as their primary function is to produce milk for nutrition of the infant and baby. There are lots of glands in our breasts, which grow and develop during puberty and maturation.
The key parts of the female breast include:. At the onset of puberty, female reproductive hormones — particularly estrogen —guide breast growth. Normal changes in the breast during pregnancy can include firming, enlarged nipples, darker nipples, and stretch marks on the skin due to enlargement. Another difference between the breasts of men and women are the amount of nerve endings in the nipples and surrounding tissues. The increased nerve endings signal milk production in mothers and can also provide a greater chance for sexual arousal when the nipples are stimulated.