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MAMMOGENESIS

MAMMOGENESIS. DEVELOPMENT OF THE MAMMARY GLAND Fetal period Prepubertal Postpubertal Pregnancy Lactation Dry off or involution. MAMMOGENESIS. Development of the mammary gland Parenchymal tissue: epithelial structures - alveoli - ducts

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MAMMOGENESIS

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  1. MAMMOGENESIS • DEVELOPMENT OF THE MAMMARY GLAND • Fetal period • Prepubertal • Postpubertal • Pregnancy • Lactation • Dry off or involution

  2. MAMMOGENESIS • Development of the mammary gland • Parenchymal tissue: epithelial structures - alveoli - ducts • Stromal Tissue:Supporting Tissues - cellular: fibroblasts, endothelial, WBC - non-cellular: collagen, connective tissue, fat pad or tissue

  3. SKIN GLAND *skin = derived from; *gland = secreting organ • holocrine secretion • - sebaceous gland - lipid • - sac structure • - cell disintegrates/ secreted • eccrine secretion • - sweat gland • - tubular structure • - no loss of cells

  4. SKIN GLAND • apocrine/ merocrine secretion • - mammary gland • - compound tubular / sacular structure • - some loss of cell components / H2O and salts

  5. FETAL DEVELOPMENT • Three distinguishable layers of cells • Ectoderm:(outer layer) - skin / nervous system • Mesoderm: (middle) - muscle / blood • endoderm: (inner) - alimentary canal

  6. MAMMARY BAND • ectoderm thickening (day 30) MAMMARY STREAK

  7. MAMMARY LINE • ectoderm thickening (day 35) MAMMARY CREST

  8. MAMMARY HILLOCK • ectoderm thickening / pushing into mesoderm Cow: day 43 .” “. ***** Human: day 49 MAMMARY BUD • Mesoderm pushes out • teat formation

  9. Mesoderm pushing out • - teat formation - skin invaginates in • ** keratin** • Ectoderm pushing in • Development of primary sprout

  10. Rodent Mammary bud Where’s it going?

  11. Primary sprout Days 80-100)

  12. Secondary sprout (days 100-130) Primary sprout : apoptosis / canalization * occurs from inside gland to streak canal

  13. Rodent newborn Connective tissue and fat in most species

  14. Primary sprout What about humans / other mammals with multiple exit ducts? Epithelial Cords (lactiferous ducts) Secondary buds

  15. AT BIRTH • Teats are well developed • - mastitis • Male gland similar • to female ( < developed) • No secretory / glandular • parts yet! • Non secretory tissue • ( blood / lymph / connective) • is well formed.

  16. PREPUBERTAL • Fat pad* / connective tissue* / duct network • **** essential**** (no secretory tissue!) • allometric growth: faster than body • ** fat deposition BUT 20X GROWTH RATE!! • isometric growth: same rate as body

  17. Rodent 4 weeks old

  18. Rodent 4 weeks old

  19. BIRTH TO PUBERTY Extensive duct development into fat pad / tissue Fat pad is ESSENTIAL!!

  20. BIRTH TO PUBERTY

  21. BIRTH TO PUBERTY How many layers thick? 1, 2, 5, ?

  22. PUBERTY TO CONCEPTION • Considerable ductal growth / branching associated with estrus cycles • TDLU : terminal ductule lobular unit • No secretory tissue / alveolus!!! • Acyclic vs. cyclic animals? • Acyclic: extended estrus in absence of • copulation (rabbit): lots of ducts/ few alveoli • Cyclic: estrus cycles, bursts of ductal • development around proestrus/ estrus

  23. PUBERTY TO CONCEPTION Extensive duct growth and branching

  24. PUBERTY TO CONCEPTION

  25. PUBERTY TO CONCEPTION

  26. PUBERTY TO CONCEPTION

  27. PREGNANCY Hamster - 94% Mouse - 78% Sheep - 78% Rabbit - 66% Rat - 60%

  28. PREGNANCY Rodent Day 9

  29. PREGNANCY Rodent Day 16

  30. PREGNANCY

  31. PREGNANCY

  32. PARTURITION - CALVING

  33. PARTURITION - CALVING

  34. PARTURITION - CALVING

  35. PARTURITION - CALVING

  36. PARTURITION - CALVING

  37. PARTURITION - CALVING

  38. PARTURITION - CALVING

  39. PARTURITION - CALVING

  40. A. Fully differentiated alveolar epithelial cells characterized by presence of numerous vacuoles (V), rounded basally positioned nuclei (N), abundant cytoplasm, and frequent occurrence of large apically located lipid droplets (F); alveolar lumen is L. B. Intermediately differentiated alveolar epithelial cells showing fewer cellular vacuoles, more irregularly shaped nuclei, and greater nuclear to cytoplasmic ratio. C. Undifferentiated alveolar epithelial cells displaying relative absence of cellular vacuoles, highly irregularly shaped nuclei, a mixture of large and small lipid droplets, and very large nuclear to cytoplasmic ratio, (X4,000).

  41. INVOLUTION

  42. INVOLUTION

  43. INVOLUTION

  44. ALVEOLUS

  45. ALVEOLUS

  46. ALVEOLUS

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