182 



APPLIED ANATOMY. 



THE MAMMA OR BREAST. 



The name mammary gland is often given to the breast, yet the latter is composed 

 not only of glandular tissue but also of fibrous and fatty tissue, with the usual vessels, 

 nerves, and lymphatics. In the male the glandular portion is undeveloped, the fat is 

 relatively scanty, and the breast as a whole is insignificant and flat. In the virgin 

 female adult it is more spheroidal. Above the nipple it is flattened and below it is 

 rounded. Its general shape is circular and it covers the chest-wall from the upper 

 border of the third rib to the sixth interspace. Laterally it reaches internally almost 

 to the sternum and externally it overlaps the edge of the pectoralis major. It lies 

 imbedded in the superficial fascia. In its development it is simply a modified seba- 

 ceous gland. Beginning by a finger-like growth from the skin it burrows its way into 

 the superficial fascia. It becomes compound and sends its branches in various direc- 

 tions, especially does it extend deeper until finally it pushes away most of the fat and 



Areola 



Areolar glands 



Nipple 



Lobule of gland-tissues 



Excretory duct 



Ampulla 

 Lactiferous duct 

 FIG. 205. The secreting structure of the breast. (Piersol.) 



rests on the fascia covering the pectoralis major muscle. This is why we find almost no 

 adipose tissue beneath the gland but mostly between the glandular structure and the 

 skin and around its edges. The shape of the virgin breast is due mainly to its adipose 

 tissue and not to its glandular structure. In those who have borne children the breasts 

 become enlarged, lax, and pendulous. After lactation is completed they again 

 retract but rarely regain their former shape. During lactation the fatty portion of the 

 breast may disappear and leave it apparently in a shriveled condition, yet such a breast 

 may be functionally quite active. Therefore the size of the breast is no criterion of its 

 milk-producing powers. 



The secreting structure, racemose in character, is divided into ten to 

 sixteen lobules each of which has its duct. These lactiferous ducts begin in the 

 acini and end in the nipple. Beneath the nipple they are dilated, each forming a 

 sinus or ampulla. While the shape of the breast is regular in its outline the 

 glandular tissue is not so. It possesses three projections or cusps. One of these 

 projects inward nearly or quite to the sternum, while the other two project toward 

 the axilla and side, one being lower than the other. These are the most common 



