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What is the breast?
The breast refers generally to the front of the chest and medically specifically
to the mammary gland.
(The word "mammary" comes from "mamma," the Greek and Latin word for the breast,
which derives from the cry "mama" uttered by infants and young children,
sometimes meaning "I want to feed at the breast.")
How is the mammary gland designed?
The mammary gland is a milk-producing structure that is composed largely of fat
cells (cells capable of storing fat). The fat deposits are laid down in the
breast under the influence of the female hormone, estrogen. Just as the surge of
estrogens at adolescence encourages this process, androgens, such as
testosterone, discourage it.
Within the mammary gland there is a complex network of branching ducts (tubes or
channels). These ducts exit from sac-like structures called lobules.
The lobules in the breast are the glands that can produce milk in females (or
rarely in males) given the appropriate hormonal stimulation.
The breast ducts transport milk from the lobules out to the nipple. The ducts
exit from the breast at the nipple.
How are human breasts different than other primates?
Human breasts are unlike those of other primates. In other primates, the breasts
grow only when the female is producing milk (lactating). When the primate female
has weaned her young, her breasts flatten back down. In humans, the breasts
develop at adolescence usually well before any pregnancy and the breasts stay
enlarged throughout the remainder of life.
What happens to the breasts in pregnancy?
During pregnancy the breasts grow further. This growth is much more uniform than
that at adolescence. The breasts of a small- busted woman tend to grow about as
much during pregnancy as those of a buxom woman. The amount of milk-producing
tissue is essentially the same. This is the reason that when milk production
begins, small-breasted women produce as much milk as do large-breasted women.
What do the nipples and surrounding pigmented tissue function?
The nipple becomes erect because of such stimuli as cold, breast feeding, and
sexual activity.
The small darkened (pigmented) area around the nipple is called the areola. (The
word "areola" is the diminutive of the Latin "area" meaning a small space.) In
pregnancy the areola darkens further and spreads in size. The areola contains
small modified sweat glands (Montgomery's glands) which secrete moisture that
acts as a lubricant for breastfeeding.
What are other internal features of the breast?
The lobules and ducts in the breast are supported by surrounding fatty tissue
and the suspensory ligaments of the breast. There are no muscles in the breast.
The characteristic bounce of the breast comes from the elasticity of the matrix
of connective tissue fibers in the breast.
There are blood vessels and lymphatics in the breast. The lymphatics are thin
channels similar to blood vessels; they do not carry blood but collect and carry
tissue fluid which ultimately reenters the blood stream. Breast tissue fluid
drains through the lymphatics into the lymph nodes located in the underarm (axilla)
and behind the breast bone (sternum).
What are cosmetic aspects of the breast?
Although the primary biologic function of the breast is to produce milk to feed
a baby, the breast has for many centuries been a symbol of femininity and
beauty.
Despite the contemporary concept of an ideal breast, there is no single model
that is ideal. The appearance of the normal female breast differs greatly from
one woman to the next and the breast of any given woman normally differs at
different times during a woman's life -- before, during and after adolescence,
during pregnancy, during the menstrual cycle, and after menopause.
How does breast tissue develop in the fetus?
Breast tissue begins to originate by the fourth week of fetal life. It grows
along two ridges, one on either side, running from the armpit (axilla) to the
crotch. These are the milk ridges or milk lines. Breast tissue can develop
anywhere along the milk line. It is quite common to have breast tissue up toward
and even in the armpit. An extra nipple can also develop anywhere along the milk
line, as can a complete auxiliary breast.
Rarely, the breast may be absent. The normal growth of the breast or nipple
never takes place and there is no sign whatsoever of the breast tissue, areola
or nipple.
Absence of the breast (also called amastia) frequently does not occur as the
only physical problem. Unilateral amastia (amastia just on one side) is often
associated with absence of the pectoral muscles (the muscles of the front of the
chest). Bilateral amastia (with absence of both breasts) is associated in 40% of
cases with multiple congenital anomalies (birth defects) involving other parts
of the body as well.
Amastia can be distinguished from amazia -- wherein breast tissue is absent, but
the nipple is present -- a condition that typically is a result of radiation or
surgery.
Source :
http://www.medicinenet.com/breast/article.htm