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2. THE BREAST / MAMMARY GLAND: The breasts are specialized accessory glands of the skin that secrete milk They are present in both sexes. In males and immature females, they are similar in structure. 2Lufukuja G

3. Development of the breast The human breast consists of the parenchyma and stroma, originating from ectodermal and mesodermal elements, respectively. The parenchyma forms a system of branching ducts eventually leading to secretory acini development and the stroma consists mainly of adipose tissue, providing the environment for development of the parenchyma Lufukuja G3

4. Development of the breast… Around day 35 of gestation, proliferation of paired areas of epithelial cells in the epidermis of the thoracic region occurs. These discrete areas of proliferation extend in a line between the fetal axilla and inguinal region and form two ridges called the mammary crests or milk lines Lufukuja G4

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6. Development of the breast… Most of the mammary crest atrophies except for paired solid epithelial masses in the pectoral region at the fourth intercostal space, which form the primary mammary buds. Supernumerary nipples (polythelia) occur in 2 to 5% of humans in a position from the groin to the axilla, supporting the existence of the mammary crest or ridge. Lufukuja G6

7. Development of the breast… Toward the end of the first trimester the primary mammary buds begin to grow downwards into the underlying mesenchyme, under an inductive influence of regulatory factors secreted by the mesenchyme. Lufukuja G7

8. 8 Repeated branching of the secondary epithelial buds and canalization occur in the third trimester

9. Development of the breast… At term, approximately 15 to 20 lobes of glandular tissue have formed, each containing a lactiferous duct that opens onto the breast surface through the mammary pit. Both the surrounding skin and the fibrous suspensory ligaments of Cooper that anchor the breast to the pectoralis major fascia provide support to the breast Lufukuja G9

10. Development of the breast… Infant Breast Soon after birth, the nipples become everted from proliferation of the underlying mesoderm, and the areolae increase in pigmentation. Development of erectile tissue in the nipple areolar complex increases response of the nipple to stimulation. Lufukuja G10

11. Development of the breast… Pubertal Male Breast Development At puberty, no further development of the breast occurs in the male due to rising testosterone concentrations. During puberty, up to 40% of boys may develop transient gynecomastia, presumably due to relative estrogen dominance Gynecomastia is secondary to ductal and stromal, but not lobular hypertrophy. Although this is transient in most cases, gynecomastia can be a distressing physical anomaly for a young male. Lufukuja G11

12. THE BREAST … In the adult female, the base of the breast, i.e. its attached surface, extends vertically from the second or third to the sixth rib, and in the transverse plane from the sternal edge medially almost to the midaxillary line laterally. However, it may extend through the deep fascia up to the apex of the axilla (the axillary tail of Spence) 12Lufukuja G

13. THE BREAST … In young adult females, each breast is a rounded eminence lying within the superficial fascia, largely anterior to the upper thorax but spreading laterally to a variable extent. The trunk superficial fascial system splits to enclose the breast to form the anterior and posterior lamellae. Posterior extensions of the superficial fascial system connect the breast to the pectoralis fascia, part of the deep fascial system. 13Lufukuja G

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15. THE BREAST … Between the breast and the deep fascia the loose connective tissue in the ‘submammary space' allows the breast some degree of movement on the deep pectoral fascia 15Lufukuja G

16. THE BREAST … The mammary gland is firmly attached to the dermis of the overlying skin, by the suspensory ligaments (of Cooper). These condensations of fibrous connective tissue, particularly well developed in the superior part of the gland, help support the mammary gland lobules. 16Lufukuja G

17. THE BREAST … During puberty, the breasts normally enlarge, owing in part to glandular development but primarily from increased fat deposition. Breast shape and size depend upon genetic, racial and dietary factors, and the age, parity and menopausal status of the individual 17Lufukuja G

18. NIPPLE AND AREOLA The nipple projects from the centre of the breast anteriorly. The level of the nipple varies widely. In females, its site is dependent on the size and shape of the breasts, but it overlies the fourth intercostal space in most young women. In the male, the nipple is usually sited in the fourth intercostal space in the midclavicular line. 18Lufukuja G

19. NIPPLE AND AREOLA The areola is the disc of skin that circles the base of the nipple. It contains numerous sweat and sebaceous glands which open directly onto the skin surface. The oily secretion of these specialized sebaceous glands acts as a protective lubricant and facilitates latching of the neonate during lactation: the glands are often visible in parous women, arranged circumferentially as small elevations, Montgomery's tubercles, around the areola close to the margin 19Lufukuja G

20. SOFT TISSUE The breasts are composed of lobes which contain a network of glandular tissue consisting of branching ducts and terminal secretory lobules in a connective tissue stroma Each breast consists of 15 to 20 lobes, which radiate out from the nipple. The main duct from each lobe opens separately on the summit of the nipple and possesses a dilated ampulla just before its termination 20Lufukuja G

21. SOFT TISSUE Each lobule is drained by a lactiferous duct, which usually opens independently on the nipple. Deep to the areola, each duct has a dilated portion, the lactiferous sinus, in which a small droplet of milk accumulates or remains in the nursing mother. As the infant begins to suckle, compression of the areola (and the lactiferous sinus beneath it) expresses the accumulated droplets and encourages the infant to continue nursing 21Lufukuja G

22. Vasculature of the Breast The breasts are supplied by branches of the axillary artery, the internal thoracic artery, and some intercostal arteries. The axillary artery supplies blood via the superior thoracic artery, the pectoral branches of the thoracoacromial artery, the lateral thoracic artery and the subscapular artery. The internal thoracic artery supplies perforating branches to the anteromedial part of the breast. The second to fourth anterior intercostal arteries supply perforating branches more laterally in the anterior thorax 22Lufukuja G

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25. Venous Drainage: Internal vertebral venous plexus Axillary vein Posterior intercostal vein Azygous vein Internal thoracic vein Intracranial saggital & transverse sinus Clavicle and humerus CIRCULUS VENOSUS 25Lufukuja G

26. Lymphatic Drainage The lymph vessels from the medial quadrants of the breast pierce the second, third, and fourth intercostal spaces and enter the thorax to drain into the lymph nodes alongside the internal thoracic artery. The lymph vessels from the lateral quadrants of the breast drain into the anterior or pectoral group of axillary nodes. It follows, therefore, that a cancer occurring in the lateral quadrants of the breast tends to spread to the axillary nodes. Thoracic metastases are difficult or impossible to treat, but the lymph nodes of the axilla can be removed surgically Lufukuja G26

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28. Lymphatic Drainage 28Lufukuja G

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30. Infraclavicular nodes Krukenberg’s tumour Supraclavicular nodes Axillary nodes Sub diaphragmatic lymph nodes Hepatic nodes Parasternal nodes Subperitoneal lymph plexus Drainage 30Lufukuja G Lymphatic Drainage…

31. The nerves of the breasts derive from the anterior and lateral cutaneous branches of the 4 th -6th intercostal nerves Nerve Supply: 31Lufukuja G

32. Polymastia and Polythelia Polymastia (supernumerary breasts) or polythelia (accessory nipples) may occur superior or inferior to the normal pair, occasionally developing in the axillary fossa or anterior abdominal wall. Supernumerary breasts usually consist of only a rudimentary nipple and areola, which may be mistaken for a mole (nevus) until they change pigmentation with the normal nipples during pregnancy. Lufukuja G32

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34. Micromastia & Macromastia Micromastia: An excessively small breast on one side occasionally occurs, resulting from lack of development. Macromastia :Diffuse hypertrophy of one or both breasts occasionally occurs at puberty in otherwise normal girls Lufukuja G34

35. Amastia Failure of breast development (amastia) Note: a nipple and/or areola may be present, but no glandular tissue Lufukuja G35

36. Gynecomastia Breast hypertrophy (Slight temporary enlargement of the breasts ) in males after puberty is relatively rare (< 1%) and may be age related or drug related (e.g., after treatment with diethylstilbestrol for prostate cancer). Lufukuja G36

37. witch's milk  At birth the breasts have reached a similar developmental stage in both sexes: the combination of fetal prolactin and maternal oestrogen may give rise to transient hyperplasia and secretion of ‘witch's milk'. Lufukuja G37