FIGURE 23.36 • Photomicrographs and diagram of a lactating mammary gland. a. Low-magnification micrograph of a fast greenosmium–stained section of a lactating mammary gland. Portions of several large lobules and an excretory duct are seen. Many of the alveoli exhibit a prominent lumen, even at this magnification. 60. b. A higher magnification of an area in a shows lipid droplets (black circular profiles) within the secretory cells of the alveoli as well as in the alveolar lumina. The arrows indicate plasma cells within the interstitial spaces. 480. c. Diagram of a lactating mammary gland epithelial cell. (Redrawn after Bloom W, Fawcett DW. A Textbook of Histology, 10th ed. Philadelphia: WB Saunders, 1975.) and infertility. This effect is caused by high levels of serum prolactin, which suppress secretion of LH. Ovulation usually for 2 to 3 years, lactational amenorrhea is the principal means of birth control.
 FOLDER 23.7 Functional Considerations: Lactation and Infertility
Almost 50% of fully breast-feeding women exhibit lacta-resumes after 6 months or earlier with a decrease in suckling tional amenorrhea (lack of menstruation during lactation) frequency. In cultures in which breast-feeding may continue
The arteries that supply the breast are derived from the thoracic branches of the axillary artery, the internal thoracic artery, and anterior intercostal arteries. Branches of the vessels pass primarily along the path of the alveolar ducts as they reach capillary beds surrounding the alveoli. Veins basically follow the path of the arteries as they return to the axillary and internal thoracic veins.
Lymphatic capillaries are located in the connective tissue surrounding the alveoli. The larger lymphatic vessels drain into axillary, supraclavicular, or parasternal lymph nodes.
The nerves that supply the breast are anterior and lateral cutaneous branches from the second to sixth intercostal nerves. The nerves convey afferent and sympathetic fibers to and from the breast. The secretory function is primarily under hormonal control, but afferent impulses associated with suckling are involved in the reflex secretion of prolactin and oxytocin.
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