Mammary gland (breast)

The mammary gland (glandulae mammaris, s. mamma; from the Greek mastos) is a paired organ, originally a modified sweat gland. In men, the gland remains underdeveloped.

The mammary gland is located at the level from the 3rd to the 4th rib, on the fascia covering the pectoralis major muscle, which is why it is also called the mammary gland. The mammary gland is loosely connected to the pectoral fascia, which ensures its mobility. On the medial side, the mammary gland approaches the edge of the sternum with its base. Approximately in the middle of the gland is the nipple of the mammary gland (papilla mammaria) with pinpoint openings at the top, through which 10-15 excretory milk ducts (ductus lactiferi) open outward. The area of skin around the nipple - the areola (areola mammae), as well as the nipple, is pigmented. In girls, it is pink, in women who have given birth - brown (brown). The skin of the areola is uneven, tubercles are visible on it, on the surface of which the ducts of the glands of the areola (glandulae areolares) open, next to which the sebaceous glands are located. In the skin of the nipple and areola there are bundles of smooth muscle cells, some of which are oriented circularly and some longitudinally. Contraction of these muscles tenses the nipple.

The body of the mammary gland (corpus mammae) consists of 15-20 lobes (lobi glandulae mammariae), separated from each other by layers of fatty tissue, penetrated by bundles of loose fibrous connective tissue. These bundles pass into ligaments that support the mammary gland (ligamenta suspensoria mammaria). The lobes consist of lobules (lobuli gl. mammariae), which have the structure of complex alveolar-tubular glands, which are located radially in relation to the nipple. The ducts of the glands (one from each lobe) open at the top of the nipple of the mammary gland. On the way to the nipple (at its base), each duct has an expansion - the lactiferous sinus (sinus lactiferi).

In childhood, the mammary gland is underdeveloped, its maturation is timed to the period of puberty. During pregnancy, the glandular tissue grows, the gland increases in size. The nipple and areola darken. Dilated blood vessels (veins) are visible through the thin skin of the gland. The gland reaches its maximum development by the end of pregnancy. After lactation, the gland decreases in size. During the climacteric period, the gland undergoes partial involution. The function of the mammary gland is closely related to the activity of the sex glands.

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Developmental anomalies of the mammary gland

There are cases of underdevelopment of one or both glands, additional (in addition to one pair) glands appear (polimastia - polymastia) or only additional nipples. In men, the glands sometimes develop according to the female type (ginaecomastia - gynecomastia).

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Vessels and nerves of the mammary gland

The branches of the 3rd-7th posterior intercostal arteries and the lateral thoracic branches of the internal thoracic artery approach the mammary gland. Deep veins accompany the arteries of the same name, superficial veins are located under the skin, where they form a broadly looped plexus. Lymphatic vessels from the mammary gland are directed to the axillary nodes, parasternal (on the same and opposite side) and deep lower cervical (supraclavicular) lymph nodes. Sensory innervation of the gland is carried out from the intercostal nerves, supraclavicular nerves (from the cervical plexus). Secretory (sympathetic) fibers penetrate the gland along with sensory nerves and blood vessels.