Читать книгу Obstetrical Nursing - Carolyn Conant Van Blarcom - Страница 11

The breasts are large, specially modified skin glands of the compound, racemose or clustering type, embedded in fat and connective tissue and abundantly supplied with nerves and blood vessels. They are situated quite remotely from the pelvic organs, but because of the intimate functional relation between the two, the breasts of the female may be regarded as accessory glands of the generative system. They exist in the male, also, but only in a rudimentary state.

Although the breasts sometimes contain milk during infancy, their true function is to secrete, in the parturient woman, suitable nourishment for the human infant during the first few months of its life.

These glands are symmetrically placed, one on each side of the chest, and occupy the space between the second and sixth ribs extending from the margin of the sternum almost to the mid-axillary line. A bed of connective tissue separates them from the underlying muscles and the ribs. (Fig. 14.)

They vary in size and shape at different ages, and with different individuals, particularly in women who have borne and nursed children, when they tend to become pendulous. But in general they are hemispherical or conical in shape with the nipple protruding from one-quarter to one-half inch from the apex. The nipples are largely composed of sensitive, erectile tissue and become more rigid and prominent during pregnancy and at the menstrual periods. Their surfaces are pierced by the orifices of the milk ducts, which are fifteen or twenty in number. (Fig. 15.)

Fig. 14.—Sagittal section of breast showing structure of secretory apparatus.

The breasts are covered with very delicate, smooth, white skin, excepting for the areolæ, those circular, pigmented areas one to four inches in diameter, which surround the nipples. The areolæ are darker in brunettes than in blonds, and in all women grow darker during pregnancy. The surface of the nipples and of the areolæ is roughened by small, shot-like lumps or papillæ known as the tubercles of Montgomery. This roughness becomes more marked during pregnancy, since the papillæ grow larger and sometimes even contain milk.

Fig. 15.—Front view of breast showing areola, tubercles of Montgomery and orifices of milk ducts.

The secretory apparatus of the breasts is divided into fifteen or twenty lobes, these in turn being divided into clusters of lobules. The lobules in turn are composed of tiny, secreting cells, called acini, in which the milk is elaborated from the blood. The acini are minute globules lined by a single layer of cells and enveloped by a very delicate membrane. Tiny ducts carry the milk from the acini to the main duct of the lobule, around which the acini cluster. These ducts empty the milk into the larger duct of the lobe, which runs straight to the nipple and opens upon the surface. Just before reaching the surface, each of these lactiferous sinuses expands into an ampulla, a minute reservoir for collecting the milk, which is secreted during the periods between nursings.

These clusters of acini uniting to form lobules with tiny ducts leading into the main duct of each lobule, closely resemble a bunch of grapes. The separate grapes correspond to the acini, their small stems correspond to the tiny ducts of the glands which lead to a larger one, and the central stem of the grape cluster, to the milk duct that opens upon the nipple.

The secretory tissue really constitutes a small part of the breasts until they begin to function. But during lactation the acini become enormously developed and enlarged. After lactation ceases, the acini assume a more or less tubal form, many of them undergoing atrophic changes.