Breasts (mammary glands)

Function

The breasts are modified apocrine sweat glands arranged in 15–20 lobes, each draining by a lactiferous duct to the nipple. Under oestrogen's build in pregnancy and prolactin's command after delivery, the lobular alveoli synthesise and secrete milk — oxytocin's let-down reflex squeezes it toward the nipple in the feeding infant's first minutes.

The gland rides the pectoral fascia in a retromammary space, suspended by Cooper's ligaments from the dermis — the ligaments that dimple when tumour pulls them taut. Lymph drains chiefly to the axillary nodes — the basis of breast cancer staging.

Blood supply

Internal thoracic perforators (medial), lateral thoracic and thoracoacromial branches — an anastomosing wreath.

Nerve supply

T4–T6 intercostal and supraclavicular fibres; T4's dermatome includes the nipple.

Clinical relevance

Breast cancer

The commonest cancer of women — screening mammography, axillary sentinel node staging and receptor-guided therapy transformed its prognosis.

Mastitis

Lactational infection through cracked nipples — painful red wedge, antibiotics and continued emptying.

Fibroadenoma

The mobile, rubbery, benign lump of young breasts — 'breast mouse'.

Related conditions

• Breast cancer