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Microscopic Anatomic Structure


The epidermis of the nipple and areola is highly pigmented and somewhat wrinkled. It is covered by keratinized, stratified squamous epithelium. The deep surface of the epidermis is invaded by unusually long dermal papillae that allow capillaries to bring blood close to the surface, giving the region a pinkish color in young, fair-skinned individuals. At puberty, the pigmentation of the nipple and areola increases and the nipple becomes more prominent. During pregnancy, the areola enlarges and the degree of pigmentation increases. Deep to the areola and nipple, bundles of smooth muscle fibers are arranged radially and circumferentially in the dense connective tissue and longitudinally along the lactiferous ducts that extend up into the nipple. These muscle fibers are responsible for the erection of nipple that occurs in response to various stimuli (for a review of the anatomy of the nipple and areola, see Giacometti and Montagna[8]).

The …