seins

Seins, the French term for breasts, are paired organs located on the chest in humans and many other mammals. They consist of glandular tissue, adipose (fat) tissue, and connective tissue, organized around the nipple and the circular pigmented area called the areola. The central feature is the nipple where several lactiferous ducts open, connecting to lobes and lobules that can produce milk in lactating individuals.

In humans, breast development begins at puberty under hormonal influence, especially estrogen. Size and shape vary widely and are influenced by genetics, body fat, age, pregnancy history, and hormonal changes.

Anatomically, the breast contains 15–20 lobes, each containing lobules that produce milk, connected by ducts that converge at the nipple. The surrounding adipose and connective tissue determine overall size and contour and provide structural support.

In addition to lactation, breasts play a role in sexual maturation and physiology. Lactation is triggered by hormonal signals, with prolactin stimulating milk production and oxytocin promoting milk ejection (the let-down reflex) during feeding.

Breasts vary greatly in appearance; asymmetry is common. Medical conditions can affect breasts, including fibrocystic changes, mastitis, and breast cancer. Routine screening and medical consultation for any unusual changes are advised; guidelines vary by country and health system.

Across cultures, breasts have different social meanings and norms related to body image, clothing, and representation in media.