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Encyclopedia > Mammary gland
Mammary gland
Cross section of the breast of a human female.
Dissection of a lactating breast.
1 - Fat
2 - Lactiferous duct/lobule
3 - Lobule
4 - Connective tissue
5 - Sinus of lactiferous duct
6 - Lactiferous duct
Latin glandula mammaria
Gray's subject #271 1267
Dorlands/Elsevier g_06/12392474

Mammary glands are the organs that, in the female mammal, produce milk for the sustenance of the young. These exocrine glands are enlarged and modified sweat glands and are the characteristic of mammals which gave the class its name. ImageMetadata File history File links Illu_breast_anatomy. ... Image File history File links Dissected_lactating_breast_gray1172. ... For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ... Lactiferous ducts are lobes of the mammary gland at the tip of the nipple. ... The term lobe generally refers to a projecting part of an object, but it can have more specific meanings. ... Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, muscle, and nervous tissue. ... The term sinus (Latin for bay, pocket, curve or bosom) is used in various contexts. ... Lactiferous ducts are lobes of the mammary gland at the tip of the nipple. ... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... Elseviers logo. ... In biology, an organ (Latin: organum, instrument, tool) is a group of tissues that perform a specific function or group of functions. ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the production of milk in female mammary glands and by the presence of: hair, three middle ear bones used in hearing, and a neocortex region in... A glass of cows milk. ... Exocrine gland refers to glands that secrete their products and temporarily store their secretions in a duct. ... In humans, there are four kinds of sudoriferous or sweat glands which differ greatly in both the composition of the sweat and its purpose. ...

Contents

Humans

Structure

The basic components of the mammary gland are the alveoli (hollow cavities, a few millimetres large) lined with milk-secreting cuboidal cells and surrounded by myoepithelial cells. These alveoli join up to form groups known as lobules, and each lobule has a lactiferous duct that drains into openings in the nipple. The myoepithelial cells can contract, similar to muscle cells, and thereby push the milk from the alveoli through the lactiferous ducts toward the nipple, where it collects in widenings (sinuses) of the ducts. As the infant begins to suckle, the hormonally mediated "let down reflex" ensues and the mother's milk is secreted into - not sucked from the gland by - the baby's mouth. Cuboidal epithelia are cube-shaped epithelial cells present in single layers (Simple cuboidal epithelium) or multiple layers (Stratified cuboidal epithelium), depending on their location in the body. ... A myoepithelial cell (myoepithelium) is a type of epithelium which has some characteristics of muscle tissue. ... Typical human female nipple and areola. ... A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ...


One distinguishes between a simple mammary gland, which consists of all the milk-secreting tissue leading to a single lactiferous duct, and a complex mammary gland, which consists of all the simple mammary glands serving one nipple.


Humans normally have two complex mammary glands, one in each breast, and each complex mammary gland consists of 10-20 simple glands. (The presence of more than two nipples is known as polythelia and the presence of more than two complex mammary glands as polymastia.) A pregnant womans breasts. ... A supernumerary nipple (also known as a third nipple, accessory nipple, polythelia or polymastia) is an additional nipple occuring in mammals including humans. ... The condition of having accessory breasts is known as polymastia, supernumerary breasts, or mammae erraticae. ...


Development and hormonal control

The development of mammary glands is controlled by hormones. The mammary glands exist in both sexes, but they are rudimentary until puberty when in response to ovarian hormones, they begin to develop in the female. Estrogen promotes formation, while testosterone inhibits it. Norepinephrine A hormone (from Greek όρμή - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ... Puberty refers to the process of physical changes by which a childs body becomes an adult body capable of reproduction. ... Estriol. ... Testosterone is a steroid hormone from the androgen group. ...


At the time of birth, the baby has lactiferous ducts but no alveoli. Little branching occurs before puberty when ovarian estrogens stimulate branching differentiation of the ducts into spherical masses of cells that will become alveoli. True secretory alveoli only develop in pregnancy, where rising levels of estrogen and progesterone cause further branching and differentiation of the duct cells, together with an increase in adipose tissue and a richer blood flow. Parturition redirects here. ... A pregnant woman near the end of her term Pregnancy is the carrying of one or more offspring in an embryonal or fetal stage of development by female mammals, including humans, inside their bodies, between the stages of conception and birth. ... Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species. ... It has been suggested that Subcutaneous fat be merged into this article or section. ... Blood flow is the flow of blood in the cardiovascular system. ...


Colostrum is secreted in late pregnancy and for the first few days after giving birth. True milk secretion (lactation) begins a few days later due to a reduction in circulating progesterone and the presence of the hormone prolactin. The suckling of the baby causes the release of the hormone oxytocin which stimulates contraction of the myoepithelial cells. Colostrum (also known as beestings or first milk) is a form of milk produced by the mammary glands in late pregnancy and the few days after giving birth. ... Kittens nursing Lactation describes the secretion of milk from the mammary glands, the process of providing that milk to the young, and the period of time that a mother lactates to feed her young. ... Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species. ... Prolactin (PRL) is a peptide hormone primarily associated with lactation. ... Oxytocin (Greek: quick birth) is a mammalian hormone that also acts as a neurotransmitter in the brain. ...


Breast cancer

As described above, the cells of mammary glands can easily be induced to grow and multiply by hormones. If this growth runs out of control, cancer results. Almost all instances of breast cancer originate in the lobules or ducts of the mammary glands. Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ... Breast cancer is cancer of breast tissue. ...


Other mammals

The number and positioning of complex and simple mammary glands varies widely in different mammals. The nipples and glands can occur anywhere along the two milk lines, two roughly-parallel lines along the ventral aspect of the body. In general most mammals develop mammary glands in pairs along these lines, with a number approximating the number of young typically birthed at a time. The number of nipples varies from 2 (in most primates, including humans, for example,) to 16 found in pigs. The Virginia Opossum has 13, one of the few mammals with an odd number[1][2]. The following table lists the number and position of glands normally found in a range of mammals: The milk lines are a thickening of the epidermis, from the upper limbs (arms) to the lower limbs (legs) in mammals of both sexes. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... Binomial name (Kerr, 1792) The Virginia Opossum (Didelphis virginiana) is the only marsupial found in North America north of the Rio Grande River. ...

Species [3] Anterior
(thoracic)
Intermediate
(abdominal)
Posterior
(Inguinal)
Total
Goat, sheep, horse
guinea pig
0 0 2 2
Cattle 0 0 4 4
Cat 2 2 0 4
Dog [4] 4 2 2-4 8-10
Mouse 6 0 4 10
Rat 6 2 4 12
Pig 6 6 4 16
elephants, primates 2 0 0 2

Male mammals typically have rudimentary mammary glands and nipples, with a few exceptions: male mice don't have nipples, and male horses lack nipples and mammary glands. The male Dyak fruit bat has lactating mammary glands. [1] Diagram of a tsetse fly, showing the head, thorax and abdomen The thorax is a division of an animals body, that lies between the head and the abdomen. ... The abdomen (from the Latin word meaning belly) is the part of the body between the pelvis and the thorax. ... The inguinal canal is a passage in the anterior abdominal wall which in men conveys the spermatic cord and in woman the round ligament. ... Species See Species and subspecies The goat is a mammal in the genus Capra, which consists of nine species: the Ibex, the West Caucasian Tur, the East Caucasian Tur, the Markhor, and the Wild Goat. ... Species See text. ... Binomial name Equus caballus Linnaeus, 1758 The horse (Equus caballus, sometimes seen as a subspecies of the Wild Horse, Equus ferus caballus) is a large odd-toed ungulate mammal, one of ten modern species of the genus Equus. ... Binomial name Cavia porcellus (Linnaeus, 1758) Guinea pigs (also called cavies) are rodents belonging to the family Caviidae and the genus Cavia, originally indigenous to the Andes. ... For general information about the genus, including other species of cattle, see Bos. ... Binomial name Felis catus Linnaeus, 1758 Synonyms Felis lybica invalid junior synonym The cat (or domestic cat, house cat) is a small carnivorous mammal. ... Trinomial name Canis lupus familiaris The dog (Canis lupus familiaris) is a domestic subspecies of the wolf, a mammal of the Canidae family of the order Carnivora. ... Feral mouse A mouse (plural mice) is a rodent that belongs to one of numerous species of small mammals. ... Species 50 species; see text *Several subfamilies of Muroids include animals called rats. ... For other uses, see Pig (disambiguation). ... Genera and Species Loxodonta Loxodonta cyclotis Loxodonta africana Elephas Elephas maximus Elephas antiquus † Elephas beyeri † Elephas celebensis † Elephas cypriotes † Elephas ekorensis † Elephas falconeri † Elephas iolensis † Elephas planifrons † Elephas platycephalus † Elephas recki † Stegodon † Mammuthus † Elephantidae (the elephants) is a family of pachyderm, and the only remaining family in the order Proboscidea... For the ecclesiastical use of this term, see primate (religion) Families 13, See classification A primate is any member of the biological order Primates, the group that contains all lemurs, monkeys, and apes, including humans. ...


Mammary glands are true protein factories, and several companies have constructed transgenic animals, mainly goats and cows, in order to produce proteins for pharmaceutical use. Complex glycoproteins such as monoclonal antibodies or antithrombin cannot be produced by genetically engineered bacteria, and the production in live mammals is much cheaper than the use of mammalian cell cultures. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A genetically modified organism (GMO) is an organism whose genetic material has been altered using the genetic engineering techniques generally known as recombinant DNA technology. ... Species See Species and subspecies The goat is a mammal in the genus Capra, which consists of nine species: the Ibex, the West Caucasian Tur, the East Caucasian Tur, the Markhor, and the Wild Goat. ... COW is an acronym for a number of things: Can of worms The COW programming language, an esoteric programming language. ... A glycoprotein is a macromolecule composed of a protein and a carbohydrate (an oligosaccharide). ... Monoclonal antibodies (mAb) are antibodies that are identical because they were produced by one type of immune cell, all clones of a single parent cell. ... Image:Antithrombin. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Epithelial cells in culture, stained for keratin (red) and DNA (green) Cell culture is the term applied when cells are grown in a synthetic environment. ...


Evolution of Mammary gland

It is believed that the mammary gland is a transformed sweat gland, more closely related to Apocrine sweat glands[citation needed]. There are many theories of how they evolved, but since they do not fossilize well, supporting such theories presents a major difficulty for the researcher. One theory proposes that mammary glands evolved from glands that were used to keep the eggs of early mammals moist.[2] A diagrammatic sectional view of the skin (magnified). ...


Examples

See also

A pregnant womans breasts. ... Typical human female nipple and areola. ... A goat kid feeding on its mothers milk Teat is an alternative word for the nipple of a mammary gland, in humans referred to as a breast, from which milk is discharged. ... A cow udder with 4 teats An udder is the mammary organ of cattle and some other mammals, including goats and sheep. ... The milk lines are a thickening of the epidermis, from the upper limbs (arms) to the lower limbs (legs) in mammals of both sexes. ... Kittens nursing Lactation describes the secretion of milk from the mammary glands, the process of providing that milk to the young, and the period of time that a mother lactates to feed her young. ... A glass of cows milk. ... Breastfeeding an infant Symbol for breastfeeding (Matt Daigle, Mothering magazine contest winner 2006) Breastfeeding is the feeding of an infant or young child with milk from a womans breasts. ... A mammary tumor is a tumor originating in the mammary gland. ... Witchs milk or neonatal milk is milk secreted from the breasts of some newborn infants. ...

External links

  • Comparative Mammary Gland Anatomy by W. L. Hurley
  • On the anatomy of the breast by Sir Astley Paston Cooper (1840). Numerous drawings, in the public domain.
  • mammary+gland at eMedicine Dictionary

eMedicine is an online clinical medical knowledge base that was founded in 1996. ...

References

  1. ^ http://digitalcollections.fiu.edu/wild/transcripts/possums1.htm
  2. ^ http://www.awrc.org/Baby%20Opossums.htm
  3. ^ Merle Cunningham, Animal Science and Industry ISBN 9780130462565
  4. ^ Dog breeds vary in number of mammary glands, larger breeds tend to have 5 pairs, smaller breeds have 4 pairs

  Results from FactBites:
 
Mammary gland - Wikipedia, the free encyclopedia (650 words)
Mammary glands are the organs that, in the female mammal, produce milk for the sustenance of the young.
The mammary glands exist in both sexes, but they are rudimentary until puberty when in response to ovarian hormones, they begin to develop in the female.
Mammary glands are true protein factories, and several companies have constructed transgenic animals, mainly goats and cows, in order to produce proteins for pharmaceutical use.
  More results at FactBites »

 
 

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