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Slide 13. The MILK LINE develops in the fetus extending from the axilla to the groin as an epidermally derived structure from the skin. The slide shows a transverse section with early branching of the MAJOR LACTIFEROUS DUCTS. Epon imbedded, Toluidine Blue staining. Photographed at 63x magnification.
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Slide 14. In females a doughnut shaped disk of STROMA, into which the branching duct tree descends, is forming several years before the onset of menses. This 2mm thick slice of breast shows the blue staining of the epithelium since nuclei stain with the hematoxylin. Arrows point to the early formation of lobules around one of the ducts. Convergence of the major lactiferous ducts is seen at the nipple. Photographed at 1x magnification.
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Slide 15. As the breast enlarges the dense connective tissue stroma is dispersed by fat (F). The rectangle denotes the area of stroma magnified in the next slide. Photographed at 1x magnification.
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Slide 16. The darkly stained balls are the cellular lobules, the hormone sensitive, potentially milk producing microorgans. They stain blue since hematoxylin stains the nuclei. Each is 1-2mm in diameter. A breast contains thousands of lobules in young adult females. Photographed at 3x magnification.
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Slide 17. Each breast is composed of 6-8 LOBES shaped like pie pieces around the nipple. Contrast material was injected into one major lactiferous duct and an x-ray was taken and illustrates the branching duct tree of a single lobe. Photographed at 1x magnification.
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Slide 18. The major lactiferous ducts converge on the nipple in the slice. Photographed at 2x magnification.
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Slide 19. This transverse cut shows some of the lactiferous ducts filled with secretions. Photographed at 1.5x magnification.
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Slide 20. Major lactiferous ducts are seen longitudinally to descend several centimeters before any blue lobules are present. This is indeed nature's nursing bottle. The area needs to be empty so that the infant can bite down on the lactiferous ducts while nursing. Photographed at 1x magnification.