Mammary gland

A mammary gland is an exocrine gland in mammals that produces milk to feed young offspring.

Mammals ( from Latin mamma "breast") are vertebrate animals constituting the class Mammalia, and characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or hair, and three middle ear bones.

A mammary gland is an exocrine gland in mammals that produces milk to feed young offspring.

Milk is a nutrient-rich, white liquid food produced by the mammary glands of mammals.

The mammary glands are arranged in organs such as the breasts in primates (for example, humans and chimpanzees), the udder in ruminants (for example, cows, goats, and deer), and the dugs of other animals (for example, dogs and cats).

In females, it serves as the mammary gland, which produces and secretes milk to feed infants.

Lactorrhea, the occasional production of milk by the glands, can occur in any mammal, but in most mammals, lactation, the production of enough milk for nursing, occurs only in phenotypic females who have gestated in recent months or years. During pregnancy, progesterone and prolactin are essential for mediating lobuloalveolar development in estrogen-primed mammary gland tissue, which occurs in preparation of lactation and nursing.

Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young.

A mammary gland is an exocrine gland in mammals that produces milk to feed young offspring.

Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, and mucous.

The mammary glands are arranged in organs such as the breasts in primates (for example, humans and chimpanzees), the udder in ruminants (for example, cows, goats, and deer), and the dugs of other animals (for example, dogs and cats).

An udder is an organ formed of the mammary glands of dairy breeds of cattle and female four-legged mammals, particularly ruminants such as goats, sheep and deer.

In a few mammalian species, male lactation can occur.

In zoology, male lactation is the production of milk from a male mammal's mammary glands.

Each lobule has a lactiferous duct that drains into openings in the nipple.

Lactiferous ducts are those ducts that converge and form a branched system connecting the nipple to the lobules of the mammary gland.

Many sources assert that mammary glands are modified sweat glands.

Ceruminous glands (which produce ear wax), mammary glands (which produce milk), and ciliary glands in the eyelids are modified apocrine sweat glands.

Each lobule has a lactiferous duct that drains into openings in the nipple. During puberty, tubule formation is coupled with branching morphogenesis which establishes the basic arboreal network of ducts emanating from the nipple.

The physiological purpose of nipples is to deliver milk to the infant, produced in the female mammary glands during lactation.

The myoepithelial cells contract under the stimulation of oxytocin, excreting the milk secreted by alveolar units into the lobule lumen toward the nipple.

Milk ejection reflex/Letdown reflex: in lactating (breastfeeding) mothers, oxytocin acts at the mammary glands, causing milk to be 'let down' into lactiferous ducts, from where it can be excreted via the nipple. Suckling by the infant at the nipple is relayed by spinal nerves to the hypothalamus. The stimulation causes neurons that make oxytocin to fire action potentials in intermittent bursts; these bursts result in the secretion of pulses of oxytocin from the neurosecretory nerve terminals of the pituitary gland.

Lactorrhea, the occasional production of milk by the glands, can occur in any mammal, but in most mammals, lactation, the production of enough milk for nursing, occurs only in phenotypic females who have gestated in recent months or years.

A distinguishing characteristic of the class Mammalia is the presence of mammary glands.

A mammary gland is a specific type of apocrine gland specialized for manufacture of colostrum when giving birth.

An example of true apocrine glands is the mammary glands, responsible for secreting breast milk.

During pregnancy, progesterone and prolactin are essential for mediating lobuloalveolar development in estrogen-primed mammary gland tissue, which occurs in preparation of lactation and nursing.

It stimulates the mammary glands to produce milk (lactation): increased serum concentrations of prolactin during pregnancy cause enlargement of the mammary glands and prepare for milk production, which normally starts when levels of progesterone fall by the end of pregnancy and a suckling stimulus is present.

During pregnancy, progesterone and prolactin are essential for mediating lobuloalveolar development in estrogen-primed mammary gland tissue, which occurs in preparation of lactation and nursing.

Estrogens through estrogen receptors (ERs) induce or upregulate the expression of the PR. One example of this is in breast tissue, where estrogens allow progesterone to mediate lobuloalveolar development.

The basic components of a mature mammary gland are the alveoli (hollow cavities, a few millimeters large) lined with milk-secreting cuboidal cells and surrounded by myoepithelial cells.

In late pregnancy and for the first few days after giving birth, colostrum is secreted.

Colostrum (known colloquially as beestings, bisnings or first milk) is the first form of milk produced by the mammary glands of mammals (including many humans) immediately following delivery of the newborn.

In any case, unlike IGF-1, GH itself is not essential for mammary gland development, and IGF-1 in conjunction with estrogen can induce normal mammary gland development without the presence of GH. In addition to IGF-1, other paracrine growth factors such as epidermal growth factor (EGF), transforming growth factor beta (TGF-β), amphiregulin, fibroblast growth factor (FGF), and hepatocyte growth factor (HGF) are involved in breast development as mediators downstream to sex hormones and GH/IGF-1.

HGF is also importantly involved in normal mammary gland development.

The protruding teats and accompanying glands can be located anywhere along the two milk lines.

The mammary ridge or mammary crest, is a primordium specific for the development of the mammary gland.

Important players include beta-1 integrin, epidermal growth factor receptor (EGFR), laminin-1/5, collagen-IV, matrix metalloproteinase(MMPs), heparan sulfate proteoglycans, and others.

The EGFR is essential for ductal development of the mammary glands, and agonists of the EGFR such as amphiregulin, TGF-α, and heregulin induce both ductal and lobuloalveolar development even in the absence of estrogen and progesterone.

The basic components of a mature mammary gland are the alveoli (hollow cavities, a few millimeters large) lined with milk-secreting cuboidal cells and surrounded by myoepithelial cells.

They are found in the sweat glands, mammary glands, lacrimal glands, and salivary glands.

In any case, unlike IGF-1, GH itself is not essential for mammary gland development, and IGF-1 in conjunction with estrogen can induce normal mammary gland development without the presence of GH. In addition to IGF-1, other paracrine growth factors such as epidermal growth factor (EGF), transforming growth factor beta (TGF-β), amphiregulin, fibroblast growth factor (FGF), and hepatocyte growth factor (HGF) are involved in breast development as mediators downstream to sex hormones and GH/IGF-1.

Estradiol and progesterone mostly induce amphiregulin expression to mediate ductal development of the mammary glands.

During puberty, tubule formation is coupled with branching morphogenesis which establishes the basic arboreal network of ducts emanating from the nipple.

A well-studied example of morphogenesis that involves ECM is mammary gland ductal branching.

However, GH itself also acts independently of IGF-1 to stimulate ductal development by upregulating estrogen receptor (ER) expression in mammary gland tissue, which is a downstream effect of mammary gland GHR activation.

First, binding of estrogen to the ER stimulates proliferation of mammary cells, with the resulting increase in cell division and DNA replication, leading to mutations.

Mammary tumor

A mammary tumor is a neoplasm originating in the mammary gland.