Breast Anatomy and Physiology
Introduction of breast
Breast are considered as a accessory reproductive organs. The breast are
large, modified sebaceous (sweat) gland which is hemi-spherical in shape
A lateral projection of breast towards the axilla known as axillary tail of
Spence. It is lies in superficial fascia of pectoral region and on pectoral
fossa.
Breast is also known as mammary gland.
Breast situation at external surface fig. 1 |
Extends of breast
(a) Vertical :- The breast are extends from 2nd to 6th rib in midclavicular line.
(b) Horizontal :- The breast are extends at horizontal from lateral boarder of
sternum to mid axillary line.
Weight of breast
The shape of the breast varies in women and weight is 200 to 300
approximately.
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Deep relations of breast
(a) Muscles :- The breast is attached deeply to pectoralis major by suspensory
ligament of copper.
It is attached to serratus anterior from lateral side and to external abdomen
oblique at inferior side.
(b) Retromammary space :- Deep to breast tissue is retromammary space which
provides free movement to breast by alveolar tissue. It is the site of breast
implantation.
Structure of breast
Internal structure of breast diagram fig-2 |
The areola is a pigmented skin and placed about the center of the breast which
contain Montgomery gland (a portion of sebaceous gland that is visible on skin
surface it enlarge during pregnancy) in surrounded line. It is about 2.5cm in
diameter. Montgomery glands also has a function of lubricant nipple during
lactation by its secretions.
The nipple of breast is muscular projection covered by pigmented skin. It is
vascular and surrounded by unstriated muscles which make it erectile. It
accomodates about 15-20 lactiferous ducts and their openings. Each milk duct
(lactiferous duct) are pulled in to the teat during nursing, the infants
tongue, facial muscles and mouth squeeze the milk from the sinuses into the
infants oropharynx. The whole breast is embedded in the subcutaneous fat.
The fat is,however, absent beneath the nipple and areola.
The mature breast consist of about 20% glandular tissue and the rest
connective tissue. The breast is composed of 12-20 lobes. Each lobe has one
excretory duct (lactiferous duct) that opens at the nipple. Each lobe has
about 10-100 lobules. Cooper's ligaments are the fibrous septa, that extend
from the skin to the underlying pectoral fascia. These ligament provide
support to the breast. One lactiferous duct drains a lobe. The lining
epithelium of the duct is cubical, becomes stratified squamous near the
openings. Each alveolus is lined by columnar epithelium where milk secretion
occurs. A network of branching longitudinal striated cells called
myoepithelial cells surround the alveoli and the smaller ducts. There is a
dense network of capillaries surrounding the alveoli. These are situated
between the basement membrane and epithelial lining. Contraction of these
cells squeezes the alveoli and ejects the milk into the larger duct. Behind
the nipple, the main duct (lactiferous) dilates to form ampulla where the
milk is stored.
Breast tissue is sensitive to the cycle changes of hormones estrogen and
progesterone. Women often feel breast tenderness and fullness during the
luteal phase of the cycle. During the follicular phase, there is
proliferation of the ductal system whereas during the luteal phase there is
dilation of the ductal system and differentiation of the alveolar cells into
secretory cells. In postmenopausal women the breast lobules and ducts
atrophy. Accessory breast or nipple can occur along the breast or milk line
which extends from the axilla to the groin. Supernumerary nipples
(polythelia) are associated with renal abnormalities (10%). Asymmetry of
breast is normal variation. Massive hypertrophy of the breast is a rare
problem.
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Sources :- DC Dutt's textbook
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