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"
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.
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