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

nipple The nipple is a raised region of tissue on the surface of the breast from which, in lactating females, breast milk, milk from the mammary gland leaves the body through the lactiferous ducts to Breastfeeding, nurse an infant. The milk can flow th ...

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 the mu ...

of the

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

. When lactogenesis occurs, under the influence of hormones, the

milk Milk is a white liquid food produced by the mammary glands of lactating mammals. It is the primary source of nutrition for young mammals (including breastfeeding, breastfed human infants) before they are able to digestion, digest solid food. ...

is moved to the nipple by the action of smooth muscle contractions along the ductal system to the tip of the nipple. 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 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 lumen (anatomy), luminal cells. These may be positive for ACTA2, alph ...

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. More generally, an areola is a small circular area on the Human body, body with a different histology from the surrounding Tissue (biology), tissue ...

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 Cell junction, junctional complexes between epithelial cells, sealing and preventing leakage of solutes and water. Th ...

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

casein Casein ( , from Latin ''caseus'' "cheese") is a family of related phosphoproteins (CSN1S1, αS1, aS2, CSN2, β, K-casein, κ) that are commonly found in mammalian milk, comprising about 80% of the proteins in cow's milk and between 20% and 60% of ...

content.

Prolactin Prolactin (PRL), also known as lactotropin and mammotropin, 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 secr ...

and/or placental lactogen 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 ma ...

is the main hormone preventing closure before birth.

Clinical significance

The majority of

breast diseases Breast diseases make up a number of conditions. The most common symptoms are a breast mass, breast pain, and nipple discharge. A majority of breast diseases are noncancerous. Although breast disease may be benign, or non-life threatening there r ...

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 a cancer that develops from breast tissue. Signs of breast cancer may include a Breast lump, lump in the breast, a change in breast shape, dimpling of the skin, Milk-rejection sign, milk rejection, fluid coming from the nipp ...

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 Breast cancer classification#Stage, Stage 0. It rarely produces symptoms or a ...

) *

phyllodes tumor Phyllodes tumors (from Greek language, Greek: ), are a rare type of Biphasic tumor, biphasic Fibroepithelial neoplasm, fibroepithelial mass that form from the periductal stromal and epithelial cells of the breast. They account for less than 1% of ...

and

intraductal papilloma Intraductal papillomas of the breast are benign lesions with an incidence of approximately 2-3% in humans. They result from abnormal proliferation of the epithelial cells lining the breast ducts. Two types of intraductal papillomas are generally ...

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 Resorption is the absorption of cells or tissue into the circulatory system, usually by osteoclasts. Types of resorption include: * Bone resorption Bone resorption is resorption of bone tissue, that is, the process by which osteoclasts break ...

in the ducts *

nonpuerperal mastitis The term nonpuerperal mastitis describes inflammatory lesions of the breast (mastitis) that occur unrelated to pregnancy and breastfeeding. It is sometimes equated with duct ectasia, but other forms can be described. Types Duct ectasia—periduc ...

is frequently caused by a similar mechanism in combination with an

infection An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...

duct ectasia Duct ectasia of the breast, mammary duct ectasia or plasma cell mastitis is a condition that occurs when a milk duct beneath the nipple widens, the duct walls thicken, and the duct fills with fluid. This is the most common cause of greenish discha ...

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

References

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

Structure

Function

Clinical significance

See also

References