Porth's Essentials of Pathophysiology, 4e

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Genitourinary and Reproductive Function

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Lymphatic system Venous system Arterial system

FIGURE 40-17. The breasts, showing the shared vascular and lymphatic supply as well as the pectoral muscles.

Pectoralis major muscle

Cooper ligament

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

Alveolar glands

Pectoralis major Pectoralis minor

Intralobular duct Lobes of gland tissue

Lobular acini

Areola

Nipple Lactiferous duct

Fat

FIGURE 40-18. The breast, showing the glandular tissue and ducts of the mammary glands.