|The Breast: cross-section scheme of the mammary gland.
1. Chest wall
2. Pectoralis muscles
6. Milk duct
7. Fatty tissue
|Latin||ductus lactiferi, tubulus lactiferi|
|Gray's||subject #271 1268|
Lactiferous ducts form a tree branched system connecting the lobules of the mammary gland to the tip of the nipple. They are also referred to as galactophores, galactophorous ducts, mammary ducts, mamillary ducts and milk ducts. They are the structures which carry milk toward the nipple in a lactating female.
Lactiferous ducts are lined by a columnar epithelium supported by myoepithelial cells. When a woman is not lactating, the lactiferous duct is frequently blocked by a keratin plug. This plug prevents bacteria from entering the duct in non-lactating women. Prior to 2005, it was thought within the areola the lactiferous duct would dilate to form the lactiferous sinus in which milk supposedly accumulates between breastfeeding sessions. However new research suggests that lactiferous sinus does not exist.
The columnar epithelium plays a key role in balancing milk production, milk stasis and resorption. The cells of the columnar epithelium form tight junctions which are regulated by hormones and local factors like pressure and casein content. Prolactin and/or placental lactogen are required for tight junction closure while progesterone is the main hormone preventing closure before birth.
The majority of breast diseases either originate from lactiferous ducts or are closely related. The high susceptibility to benign and malignant diseases is in part a consequence of the cycling hormonal growth stimulation resulting in a high cell turnover and accumulation of defects and complicated hormonal equilibrium which is highly sensible to disturbance.
- most breast cancers arise from the ductal epithelium
- phyllodes tumor and intraductal papilloma of the breast
- mastalgia is frequently caused by an imbalance of breast secretion in the lobules and resorption in the ducts
- nonpuerperal mastitis is frequently caused by a similar mechanism in combination with an infection
- duct ectasia is similar and overlapping with the above mentioned
- subareolar abscess and squamous metaplasia of lactiferous ducts
- most forms of fibrocystic breast changes and cysts are thought to originate from lactiferous ducts
- Ramsay, D. T.; Kent, J. C.; Hartmann, R. A.; Hartmann, P. E. (2005). "Anatomy of the lactating human breast redefined with ultrasound imaging". Journal of Anatomy 206 (6): 525–534. doi:10.1111/j.1469-7580.2005.00417.x. PMC 1571528. PMID 15960763.
- Nguyen, D. A.; Parlow, A. F.; Neville, M. C. (2001). "Hormonal regulation of tight junction closure in the mouse mammary epithelium during the transition from pregnancy to lactation". The Journal of endocrinology 170 (2): 347–356. doi:10.1677/joe.0.1700347. PMID 11479131.
- Nguyen, D. A.; Neville, M. C. (1998). "Tight junction regulation in the mammary gland". Journal of Mammary Gland Biology and Neoplasia 3 (3): 233–246. doi:10.1023/A:1018707309361. PMID 10819511.