Реферат на тему:

Mammary gland (Endocrine system)

Mammary glands are the HYPERLINK
«http://en.wikipedia.org/wiki/Organ_(anatomy)» \o «Organ (anatomy)»
organs that, in HYPERLINK «http://en.wikipedia.org/wiki/Mammal» \o
«Mammal» mammals , produce HYPERLINK
«http://en.wikipedia.org/wiki/Milk» \o «Milk» milk for the sustenance
of the young. These HYPERLINK
«http://en.wikipedia.org/wiki/Exocrine_gland» \o «Exocrine gland»
exocrine glands are enlarged and modified HYPERLINK
«http://en.wikipedia.org/wiki/Sweat_gland» \o «Sweat gland» sweat
glands and give mammals their name. The mammary glands of domestic
mammals containing more than two breasts are called dugs.



The basic components of the mammary gland are the alveoli (hollow
cavities, a few millimetres large) lined with milk-secreting HYPERLINK
«http://en.wikipedia.org/wiki/Cuboidal_cells» \o «Cuboidal cells»
cuboidal cells and surrounded by HYPERLINK
«http://en.wikipedia.org/wiki/Myoepithelial_cell» \o «Myoepithelial
cell» 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 HYPERLINK «http://en.wikipedia.org/wiki/Nipple» \o
«Nipple» nipple . The myoepithelial cells can contract under the
stimulation of HYPERLINK «http://en.wikipedia.org/wiki/Oxytocin» \o
«Oxytocin» oxytocin thereby excreting the milk from glands through the
lactiferous ducts toward the nipple, where it collects in sinuses of the
ducts. As the infant begins to suck, the hormonally (oxytocin) mediated
«let down reflex» ensues and the mother’s milk is secreted into – not
sucked from the gland by – the baby’s mouth.

All the milk-secreting tissue leading to a single lactiferous duct is
called a «simple mammary gland»; a «complex mammary gland» is all the
simple mammary glands serving one nipple. Humans normally have two
complex mammary glands, one in each HYPERLINK
«http://en.wikipedia.org/wiki/Breast» \o «Breast» breast , and each
complex mammary gland consists of 10–20 simple glands. The presence of
more than two nipples is known as HYPERLINK
«http://en.wikipedia.org/wiki/Polythelia» \o «Polythelia» polythelia
and the presence of more than two complex mammary glands as HYPERLINK
«http://en.wikipedia.org/wiki/Accessory_breast» \o «Accessory breast»
polymastia .

Development and hormonal control

Mammary glands exist in both sexes, but are rudimentary until
HYPERLINK «http://en.wikipedia.org/wiki/Puberty» \o «Puberty» puberty
when, in females, they begin to develop in response to HYPERLINK
«http://en.wikipedia.org/wiki/Ovarian» \o «Ovarian» ovarian hormones.
HYPERLINK «http://en.wikipedia.org/wiki/Estrogen» \o «Estrogen»
Estrogen promotes formation, whereas HYPERLINK
«http://en.wikipedia.org/wiki/Testosterone» \o «Testosterone»
testosterone inhibits it.

At the time of HYPERLINK «http://en.wikipedia.org/wiki/Childbirth» \o
«Childbirth» 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
HYPERLINK «http://en.wikipedia.org/wiki/Pregnancy» \o «Pregnancy»
pregnancy , where rising levels of estrogen and HYPERLINK
«http://en.wikipedia.org/wiki/Progesterone» \o «Progesterone»
progesterone cause further branching and differentiation of the duct
cells, together with an increase in HYPERLINK
«http://en.wikipedia.org/wiki/Adipose_tissue» \o «Adipose tissue»
adipose tissue and a richer HYPERLINK
«http://en.wikipedia.org/wiki/Blood_flow» \o «Blood flow» blood flow .

HYPERLINK «http://en.wikipedia.org/wiki/Colostrum» \o «Colostrum»
Colostrum is secreted in late pregnancy and for the first few days
after giving birth. True milk secretion ( HYPERLINK
«http://en.wikipedia.org/wiki/Lactation» \o «Lactation» lactation )
begins a few days later due to a reduction in circulating HYPERLINK
«http://en.wikipedia.org/wiki/Progesterone» \o «Progesterone»
progesterone and the presence of the hormone HYPERLINK
«http://en.wikipedia.org/wiki/Prolactin» \o «Prolactin» prolactin . The
suckling of the baby causes the release of the hormone HYPERLINK
«http://en.wikipedia.org/wiki/Oxytocin» \o «Oxytocin» oxytocin which
stimulates contraction of the myoepithelial cells.

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,
HYPERLINK «http://en.wikipedia.org/wiki/Cancer» \o «Cancer» cancer
results. Almost all instances of HYPERLINK
«http://en.wikipedia.org/wiki/Breast_cancer» \o «Breast cancer» breast
cancer originate in the lobules or ducts of the mammary glands.

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 HYPERLINK «http://en.wikipedia.org/wiki/Milk_line» \o
«Milk line» milk lines , two roughly-parallel lines along the
HYPERLINK «http://en.wikipedia.org/wiki/Ventral» \o «Ventral» 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) to 16 (in pigs). The HYPERLINK
«http://en.wikipedia.org/wiki/Virginia_Opossum» \o «Virginia Opossum»
Virginia Opossum has 13, one of the few mammals with an odd number
HYPERLINK «http://en.wikipedia.org/wiki/Mammary_gland» \l «cite_note-0»
\o «» [1] HYPERLINK «http://en.wikipedia.org/wiki/Mammary_gland» \l
«cite_note-1» \o «» [2] . The following table lists the number and
position of glands normally found in a range of mammals:

Species HYPERLINK «http://en.wikipedia.org/wiki/Mammary_gland» \l
«cite_note-2» \o «» [3] Anterior

( HYPERLINK «http://en.wikipedia.org/wiki/Thoracic» \o «Thoracic»
thoracic ) Intermediate

( HYPERLINK «http://en.wikipedia.org/wiki/Abdominal» \o «Abdominal»
abdominal ) Posterior

( HYPERLINK «http://en.wikipedia.org/wiki/Inguinal» \o «Inguinal»
Inguinal ) Total

HYPERLINK «http://en.wikipedia.org/wiki/Goat» \o «Goat» Goat ,
HYPERLINK «http://en.wikipedia.org/wiki/Sheep» \o «Sheep» sheep ,
HYPERLINK «http://en.wikipedia.org/wiki/Horse» \o «Horse» horse

HYPERLINK «http://en.wikipedia.org/wiki/Guinea_pig» \o «Guinea pig»
guinea pig 0 0 2 2

HYPERLINK «http://en.wikipedia.org/wiki/Cattle» \o «Cattle» Cattle 0
0 4 4

HYPERLINK «http://en.wikipedia.org/wiki/Cat» \o «Cat» Cat 2 2 2 6

HYPERLINK «http://en.wikipedia.org/wiki/Dog» \o «Dog» Dog
HYPERLINK «http://en.wikipedia.org/wiki/Mammary_gland» \l «cite_note-3»
\o «» [4] 4 2 2 or 4 8 or 10

HYPERLINK «http://en.wikipedia.org/wiki/Mouse» \o «Mouse» Mouse 6 0
4 10

HYPERLINK «http://en.wikipedia.org/wiki/Rat» \o «Rat» Rat 6 2 4 12

HYPERLINK «http://en.wikipedia.org/wiki/Pig» \o «Pig» Pig 6 6 4 16

HYPERLINK «http://en.wikipedia.org/wiki/Elephant» \o «Elephant»
Elephants , HYPERLINK «http://en.wikipedia.org/wiki/Primates» \o
«Primates» 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.[ HYPERLINK
«http://en.wikipedia.org/wiki/Wikipedia:Citation_needed» \o
«Wikipedia:Citation needed» citation needed ] The male Dyak fruit bat
has lactating mammary glands; HYPERLINK
«http://en.wikipedia.org/wiki/Mammary_gland» \l «cite_note-4» \o «» [5]
HYPERLINK «http://en.wikipedia.org/wiki/Male_lactation» \o «Male
lactation» male lactation occurs infrequently in some species,
including humans.

Mammary glands are true HYPERLINK
«http://en.wikipedia.org/wiki/Protein» \o «Protein» protein factories,
and several companies have constructed HYPERLINK
«http://en.wikipedia.org/wiki/Genetically_modified_organism» \o
«Genetically modified organism» transgenic animals , mainly HYPERLINK
«http://en.wikipedia.org/wiki/Goat» \o «Goat» goats and HYPERLINK
«http://en.wikipedia.org/wiki/Cow» \o «Cow» cows , in order to produce
proteins for pharmaceutical use. Complex HYPERLINK
«http://en.wikipedia.org/wiki/Glycoprotein» \o «Glycoprotein»
glycoproteins such as HYPERLINK
«http://en.wikipedia.org/wiki/Monoclonal_antibody» \o «Monoclonal
antibody» monoclonal antibodies or HYPERLINK
«http://en.wikipedia.org/wiki/Antithrombin» \o «Antithrombin»
antithrombin cannot be produced by genetically engineered HYPERLINK
«http://en.wikipedia.org/wiki/Bacteria» \o «Bacteria» bacteria , and
the production in live mammals is much cheaper than the use of mammalian
HYPERLINK «http://en.wikipedia.org/wiki/Cell_culture» \o «Cell
culture» cell cultures .


It is believed that the mammary gland is a transformed sweat gland,
more closely related to HYPERLINK
«http://en.wikipedia.org/wiki/Apocrine_sweat_glands» \o «Apocrine sweat
glands» Apocrine sweat glands . 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. HYPERLINK
edalolav20030714.cfm» \o
edalolav20030714.cfm» [


HYPERLINK «http://en.wikipedia.org/wiki/Mammary_gland» \l «cite_ref-0»
«http://digitalcollections.fiu.edu/wild/transcripts/possums1.htm» \o
«http://digitalcollections.fiu.edu/wild/transcripts/possums1.htm» With
the Wild Things — Transcripts

HYPERLINK «http://en.wikipedia.org/wiki/Mammary_gland» \l «cite_ref-1»
\o «» ^ HYPERLINK «http://www.awrc.org/Baby%20Opossums.htm» \o
«http://www.awrc.org/Baby%20Opossums.htm» Raising Orphaned Baby

HYPERLINK «http://en.wikipedia.org/wiki/Mammary_gland» \l «cite_ref-2»
\o «» ^ Merle Cunningham, Animal Science and Industry HYPERLINK
«http://en.wikipedia.org/wiki/Special:BookSources/9780130462565» ISBN

HYPERLINK «http://en.wikipedia.org/wiki/Mammary_gland» \l «cite_ref-3»
\o «» ^ Dog breeds vary in the number of mammary glands: larger breeds
tend to have 5 pairs, smaller breeds have 4 pairs.

HYPERLINK «http://en.wikipedia.org/wiki/Mammary_gland» \l «cite_ref-4»
\o «» ^ Francis, Charles M.; Anthony, Edythe L. P.; Brunton, Jennifer
A.; Kunz, Thomas H. ( HYPERLINK «http://en.wikipedia.org/wiki/1994» \o
«1994» 1994 — HYPERLINK «http://en.wikipedia.org/wiki/February_24» \o
«February 24″ 02-24 ). » HYPERLINK
«http://www.nature.com/nature/journal/v367/n6465/abs/367691a0.html» \o
Lactation in male fruit bats «. Nature (Nature Publishing Group) 367:
691–692. HYPERLINK
«http://en.wikipedia.org/wiki/Digital_object_identifier» \o «Digital
object identifier» doi : HYPERLINK
«http://dx.doi.org/10.1038%2F367691a0» \o
«http://dx.doi.org/10.1038%2F367691a0» 10.1038/367691a0 . HYPERLINK
«http://www.nature.com/nature/journal/v367/n6465/abs/367691a0.html» \o
http://www.nature.com/nature/journal/v367/n6465/abs/367691a0.html .
Retrieved on 2008-05-14. 

External links

nSci308/anatomycompar.html» \o
AnSci308/anatomycompar.html» Comparative Mammary Gland Anatomy by W.
L. Hurley

HYPERLINK «http://jdc.jefferson.edu/cooper/61/» \o
«http://jdc.jefferson.edu/cooper/61/» On the anatomy of the breast by
Sir Astley Paston Cooper (1840). Numerous drawings, in the public

y+gland» \o
y+gland» mammary+gland at HYPERLINK
«http://en.wikipedia.org/wiki/EMedicine» \o «EMedicine» eMedicine

Dissection of a lactating breast.

1 — HYPERLINK «http://en.wikipedia.org/wiki/Fat» \o «Fat» Fat

2 — HYPERLINK «http://en.wikipedia.org/wiki/Lactiferous_duct» \o
«Lactiferous duct» Lactiferous duct /lobule

3 — HYPERLINK «http://en.wikipedia.org/wiki/Lobule» \o «Lobule»

4 — HYPERLINK «http://en.wikipedia.org/wiki/Connective_tissue» \o
«Connective tissue» Connective tissue

5 — HYPERLINK «http://en.wikipedia.org/wiki/Sinus_(anatomy)» \o «Sinus
(anatomy)» Sinus of lactiferous duct














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? HYPERLINK «http://en.wikipedia.org/wiki/Lactiferous_duct» \o
«Lactiferous duct» Lactiferous duct

glandula mammaria

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