|Henry Gray (18251861). Anatomy of the Human Body. 1918.|
|to twenty; they are termed the tubuli lactiferi. They converge toward the areola, beneath which they form dilatations or ampullæ, which serve as reservoirs for the milk, and, at the base of the papillæ, become contracted, and pursue a straight course to its summit, perforating it by separate orifices considerably narrower than the ducts themselves. The ducts are composed of areolar tissue containing longitudinal and transverse elastic fibers; muscular fibers are entirely absent; they are lined by columnar epithelium resting on a basement membrane. The epithelium of the mamma differs according to the state of activity of the organ. In the gland of a woman who is not pregnant or suckling, the alveoli are very small and solid, being filled with a mass of granular polyhedral cells. During pregnancy the alveoli enlarge, and the cells undergo rapid multiplication. At the commencement of lactation, the cells in the center of the alveolus undergo fatty degeneration, and are eliminated in the first milk, as colostrum corpuscles. The peripheral cells of the alveolus remain, and form a single layer of granular, short columnar cells, with spherical nuclei, lining the basement membrane. The cells, during the state of activity of the gland, are capable of forming, in their interior, oil globules, which are then ejected into the lumen of the alveolus, and constitute the milk globules. When the acini are distended by the accumulation of the secretion the lining epithelium becomes flattened.|
FIG. 1172 Dissection of the lower half of the mamma during the period of lactation. (Luschka.) (See enlarged image)
FIG. 1173 Section of portion of mamma. (See enlarged image)
| The fibrous tissue invests the entire surface of the mamma, and sends down septa between its lobes, connecting them together.|
| The fatty tissue covers the surface of the gland, and occupies the interval between its lobes. It usually exists in considerable abundance, and determines the form and size of the gland. There is no fat immediately beneath the areola and papilla.|
Vessels and Nerves.The arteries supplying the mammæ are derived from the thoracic branches of the axillary, the intercostals, and the internal mammary. The veins describe an anastomotic circle around the base of the papilla, called by Haller the circulus venosus. From this, large branches transmit the blood to the circumference of the gland, and end in the axillary and internal mammary veins. The lymphatics are described on page 715. The nerves are derived from the anterior and lateral cutaneous branches of the fourth, fifth, and sixth thoracic nerves.