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U N I T 1 1
Genitourinary and Reproductive Function
ducts and alveolar glands of the lobules—myoepithelial
and luminal epithelial cells. Contractile epithelial cells,
which lie between the surface epithelium and the base-
ment membrane, provide structural support for the lob-
ules, and assist in milk ejection during lactation. The
luminal epithelial cells, which are the only cells capable
of producing milk, overlie the myoepithelial cells.
The structure of the breast changes with the men-
strual cycle and pregnancy. Estrogen stimulates the
growth of the ductal system, whereas progesterone stim-
ulates the growth and development of the ductile and
glandular secretory epithelium. Early in the menstrual
cycle, the ducts appear as cords with little or no lumen.
Under estrogen stimulation, at the time of ovulation,
the secretory cells increase in size, lumina appear in the
ducts as small amounts of secretions accumulate, and
fluid collects in the connective tissue. This causes a feel-
ing of breast fullness and discomfort. During pregnancy,
placental estrogen and progesterone produce further
changes in the mammary glands. Beginning at about the
5th week of pregnancy, the anterior pituitary releases
increasing amounts of the hormone
prolactin
. The alve-
olar glands are lined with secretory cells capable of pro-
ducing milk under the influence of prolactin. However,
milk production does not occur until after birth. This
is because placental hormones inhibit milk production.
Following childbirth and expulsion of the placenta, the
maternal concentration of placental hormones declines
rapidly and the action of prolactin is no longer inhibited.
Benign Disorders
Breast disease may be described as benign or cancer-
ous.
56–58
Benign breast conditions are nonmalignant con-
ditions of the breast. They include inflammatory disorders
and benign epithelial disorders. Some benign disorders
may increase the risk of malignant disease and others
may present with signs that resemble malignant disease.
Inflammatory Disorders
Inflammatory diseases of the breast are uncommon,
accounting for less than 1% of breast disorders. They
include mastitis, mammary duct ectasia, and fat necrosis.
Mastitis.
Mastitis is inflammation of the breast.
57,58
It
most frequently occurs during lactation but may also
result from other disorders. In the lactating woman,
inflammation results from an ascending infection that
travels from the nipple to the ductal structures. The
most common organisms isolated are
Staphylococcus
aureus
and
Streptococcus
.
57
The offending organisms
often originate from the suckling infant’s nasopharynx
or the mother’s hands. During the early weeks of nurs-
ing, the breast is particularly vulnerable to bacterial
invasion because of minor cracks and fissures that
occur with vigorous suckling. Infection and inflamma-
tion cause obstruction of the ductal system. The breast
area becomes hard, inflamed, and tender if not treated
early. Without treatment, the area becomes walled off
and may abscess, requiring incision and drainage. It is
Nipple
Lactiferous duct
Fat
Pectoralis major
Alveolar glands
Pectoralis minor
Intralobular duct
Lobes of
gland tissue
Lobular
acini
Areola
FIGURE 40-18.
The breast, showing the glandular tissue
and ducts of the mammary glands.
Lymphatic system
Venous system
Arterial system
Pectoralis major
muscle
Cooper
ligament
FIGURE 40-17.
The breasts,
showing the shared vascular and
lymphatic supply as well as the
pectoral muscles.
