10.2. Breast: Structure
‘Glandular tissue’ refers to the lobes, lobules, bulbs and lactiferous ducts of the breast. There are 15 – 20 lobes, each composed of smaller lobules which have bulbs at their ends that produce milk. This milk is carried to the nipple via numerous ducts, which end as 15 – 20 terminal lactiferous ducts. Each duct opens at the nipple at a separate orifice.
‘Fibrous tissue’ refers mainly to the suspensory ligaments of Cooper. These are fibrous strands that run in-between the glandular and adipose tissue, connecting the superficial fascia of the thoracic wall to the superficial fascia lying under the skin and the nipple. 'Adipose tissue', or fatty tissue, is distributed throughout the breast.
The Nipple, Areola and Glands
The nipple is also called the 'mammary papilla'. It is a cylindrical projection from a point just below the centre of the breast. In women who have not had a child, the nipple typically lies at the level of the fourth intercostal space. The lactiferous ducts run through the breast to converge and open up at the tip of the nipple. The nipple also contains smooth muscle fibres that cause the nipple to become erect when mechanical stimulation occurs during suckling by the baby.
The base of the nipple is surrounded by an area of coloured skin called the areola. In a woman who has not had a child, the areola is pink. During the second month of pregnancy the areola becomes larger and darker in colour. By the ninth month of pregnancy it is dark brown. During lactation, this dark brown colour lightens somewhat.
Sebaceous areolar glands are present too. They are small until pregnancy and lactation, at which stage they enlarge to secrete an oily substance that acts as a protective lubricant for the nipple and areola during lactation and the suckling of the baby. When the glands enlarge during pregnancy and lactation, they form tubercles under the skin are so are renamed ‘the tubercles of Montgomery’.