Lactiferous ducts are ducts that converge and form a branched system connecting the nipple to the

lobules In anatomy, a lobe is a clear anatomical division or extension of an organ (as seen for example in the brain, lung, liver, or kidney) that can be determined without the use of a microscope at the gross anatomy level. This is in contrast to t ...

of the

mammary gland A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in ...

. When lactogenesis occurs, under the influence of hormones, the milk is moved to the nipple by the action of smooth muscle contractions along the ductal system to the tip of the

nipple The nipple is a raised region of tissue on the surface of the breast from which, in females, milk leaves the breast through the lactiferous ducts to feed an infant. The milk can flow through the nipple passively or it can be ejected by smooth ...

. They are also referred to as ''galactophores'', ''galactophorous ducts'', ''mammary ducts'', ''mamillary ducts'' or ''milk ducts''.

Structure

Lactiferous ducts are lined by a

columnar epithelium Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...

supported by

myoepithelial cell Myoepithelial cells (sometimes referred to as myoepithelium) are cells usually found in glandular epithelium as a thin layer above the basement membrane but generally beneath the luminal cells. These may be positive for alpha smooth muscle actin a ...

s. Prior to 2005, it was thought within the

areola The human areola (''areola mammae'', or ) is the pigmented area on the breast around the nipple. Areola, more generally, is a small circular area on the body with a different histology from the surrounding tissue, or other small circular ...

the lactiferous duct would dilate to form the lactiferous sinus in which milk accumulates between breastfeeding sessions. However past studies have shown that the lactiferous sinus does not exist.

Function

The columnar epithelium plays a key role in balancing milk production, milk stasis and reabsorption. The cells of the columnar epithelium form

tight junction Tight junctions, also known as occluding junctions or ''zonulae occludentes'' (singular, ''zonula occludens''), are multiprotein junctional complexes whose canonical function is to prevent leakage of solutes and water and seals between the epith ...

s which are regulated by hormones and local factors like pressure and

casein Casein ( , from Latin ''caseus'' "cheese") is a family of related phosphoproteins ( αS1, aS2, β, κ) that are commonly found in mammalian milk, comprising about 80% of the proteins in cow's milk and between 20% and 60% of the proteins in hum ...

content.

Prolactin Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secreted from the pi ...

and/or

placental lactogen Placental lactogen, also called chorionic somatomammotropin, is a polypeptide placental hormone, part of the somatotropin family. Its structure and function is similar to that of growth hormone. It modifies the metabolic state of the mother during ...

are required for tight junction closure while

progesterone Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the majo ...

is the main hormone preventing closure before birth.

Clinical significance

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 sensitive to disturbance. * most

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or ...

s arise from the ductal epithelium (see

ductal carcinoma in situ Ductal carcinoma in situ (DCIS), also known as intraductal carcinoma, is a pre-cancerous or non-invasive cancerous lesion of the breast. DCIS is classified as Stage 0. It rarely produces symptoms or a breast lump one can feel, typically being d ...

) * phyllodes tumor and intraductal papilloma of the breast *

mastalgia Breast pain is the symptom of discomfort in either one or both breasts. Pain in both breasts is often described as ''breast tenderness'', is usually associated with the menstrual period and is not serious. Pain that involves only one part of a b ...

is frequently caused by an imbalance of breast secretion in the

and resorption in the ducts * nonpuerperal mastitis is frequently caused by a similar mechanism in combination with an

infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...

* 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

Lactiferous Duct Dysmorphia (LDD)

Lactiferous Duct Dysmorphia (LDD) is the deformity or abnormality in the shape or size of a milk duct negatively affecting milk flow (also known as Milk Duct Dysmorphia). Typical causes include: nipple clamps, piercings, or most commonly, ill fitting breast pump flanges.

References

{{DEFAULTSORT:Lactiferous Duct Breast anatomy Human female endocrine system

Structure

Function

Clinical significance

Lactiferous Duct Dysmorphia (LDD)

See also

References