Mammary gland

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The breasts are found at the anterior thoracic wall, anterior to the deep fascia and pectoral muscles; separated from them by the retromammary space. Each breast consists of mammary glands and surrounding connective tissue.

The mammary glands are modified apocrine sweat glands. They are structurally dynamic, meaning that the anatomy changes depending on a woman’s age, menstrual cycle phase and reproductive status. The glands are active in adult women after childbirth (postpartum period).

The gland is comprised of 15-20 secretory lobes which are separated by fibrous bands called the suspensory ligaments of the breast (of Cooper). The secretory lobes contain numerous lobules comprised of the tubuloalveolar glands. The secretory ducts of the lobes, called the lactiferous ducts, converge and open into the nipple. Each lactiferous duct dilates into the lactiferous sinus before opening onto the nipple. Near their openings, the lactiferous ducts are lined with stratified squamous keratinized epithelium. 

Histologically, there are two main types of cells associated with mammary ducts and lobules, glandular epithelial and myoepithelial cells. Glandular epithelial cells are found lining the duct system, whereas myoepithelial cells reside deep within the epithelium between the epithelial cells and the basal lamina. The myoepithelial cells have a further function: their contraction assists in milk ejection during lactation.

In addition, the areola, the circular roughened pigmented skin surrounding the nipple, contains sweat and sebaceous glands, as well as the modified mammary glands called areolar glands (of Montgomery). Their function is to produce an antimicrobial secretion that protects the surface of areola.

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