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НазваMammary gland (Endocrine system) (реферат)
РозділІноземна мова, реферати англійською, німецькою
ФорматWord Doc
Тип документуРеферат
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Реферат на тему: 

Mammary gland (Endocrine system)


Mammary glands are the   HYPERLINK
"" \o "Organ (anatomy)" 
organs  that, in   HYPERLINK "" \o
"Mammal"  mammals , produce   HYPERLINK
"" \o "Milk"  milk  for the sustenance
of the young. These   HYPERLINK
"" \o "Exocrine gland" 
exocrine glands  are enlarged and modified   HYPERLINK
"" \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
"" \o "Cuboidal cells" 
cuboidal cells  and surrounded by   HYPERLINK
"" \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 "" \o
"Nipple"  nipple . The myoepithelial cells can contract under the
stimulation of   HYPERLINK "" \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
"" \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
"" \o "Polythelia"  polythelia 
and the presence of more than two complex mammary glands as   HYPERLINK
"" \o "Accessory breast" 
polymastia .

Development and hormonal control

Mammary glands exist in both sexes, but are rudimentary until  
HYPERLINK "" \o "Puberty"  puberty 
when, in females, they begin to develop in response to   HYPERLINK
"" \o "Ovarian"  ovarian  hormones. 
 HYPERLINK "" \o "Estrogen" 
Estrogen  promotes formation, whereas   HYPERLINK
"" \o "Testosterone" 
testosterone  inhibits it.

At the time of   HYPERLINK "" \o
"Childbirth"  birth , the baby has lactiferous ducts but no alveoli.
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