The mammary gland is the milk-producing tissue of the breast, a modified sweat gland. It is arranged as 15-20 lobes radiating from the nipple, each made of many small lobules of milk-secreting alveoli draining into a duct system. It stays mostly inactive until pregnancy, when it greatly expands under hormonal control.
| Location | Within the breast, mostly in the upper outer quadrant and axillary tail, embedded in fat superficial to the pectoral fascia |
|---|---|
| Parts |
|
| Nerve Supply | Anterior and lateral cutaneous branches of the 4th-6th intercostal nerves; Sympathetic fibres (to smooth muscle and vessels) |
| Blood Supply | Internal thoracic artery (perforating and medial mammary branches); Lateral thoracic artery; Thoracoacromial artery (pectoral branches); Posterior intercostal arteries (2nd-4th, lateral branches) |
| Venous drainage |
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| Lymphatic drainage |
|
Produces milk under the influence of prolactin and ejects it via myoepithelial contraction under oxytocin.
Glandular tissue is denser in younger women, which makes mammograms harder to read. The terminal duct lobular unit is where most breast cancers and many benign changes, such as cysts and fibrocystic change, begin. Prolactin drives milk production after birth, and a prolactin-secreting pituitary tumour can cause milk discharge outside pregnancy.
Inflammation of the breast tissue, usually during breastfeeding, with a painful, red, hot area and sometimes fever.
Lumpy, sometimes tender breast tissue that varies with the menstrual cycle; benign.
A fluid-filled sac in the glandular tissue, common in women in their 40s.
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