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Bone

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bone histology and morphology

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Bone

  1. 1. BONE Dr Laxman KhanalMS- Human Anatomy Batch-2011 Date-25-04-2012
  2. 2. OBJECTIVES….• Introduction• Functions.• Embryological source of bone.• Parts of bones• Laws of ossification• Blood supply of bones• Classification of bones25/27/2012 1212413114 2
  3. 3. …OBJECTIVES• Microscopic study of bones.Compact and cancellous bone• Composition of bones.• Ossification of bones. Intramembranous Endochondral• Growth of bones• Factors affecting the bone25/27/2012 1212413114 3
  4. 4. Introduction• Bone is mineralized dense connective tissue• Made up of few cells in mineralized matrix• Consists of 30-40 % of our body weight.• Dynamic in nature25/27/2012 1212413114 4
  5. 5. Function• Framework of the body.• Attachment of muscle and tendon.• Permit the movements in body parts.• Protection of organs.• Haematopoiesis• Reservoir of minerals and fat.25/27/2012 1212413114 5
  6. 6. Embryological source• Embryonic mesodermal cells• Neural crest cellsPrimodial for the different types of cells.25/27/2012 1212413114 6
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  8. 8. Parts of bones• Epiphysis – secondary centersPressure epiphysisTraction epiphysisAtavistic epiphysis• Diaphysis – primary centerStrongest part of bone25/27/2012 1212413114 8
  9. 9. epiphysis diaphysis epiphysis25/27/2012 1212413114 9
  10. 10. • Metaphysis- epiphysial ends of a diaphysisMaximum blood supply• Epiphysial plate of cartilage- separate epiphysis from metaphysis.Maximum growth25/27/2012 1212413114 10
  11. 11. •Medullary cavity medullary cavity • filled with yellow marrow in adults • lined with endosteum25/27/2012 1212413114 11
  12. 12. Principles of Ossification• Primary ossification center –before birth• Secondary ossification center- after birth• Ossification center which appears first is usually last to fuse except for Fibula.• In long bone with single epiphysis, that epiphysis is at the movable end25/27/2012 1212413114 12
  13. 13. Principles of ossification• Larger the epiphysis earlier the ossification center appears in long bone• If epiphysis develops from more than one centers the various centers coalesce before union occurs with the diaphysis.• When epiphysis fuses with the diaphysis the growth ceases.• This fusion occurs 1 year earlier in females than in males.25/27/2012 1212413114 13
  14. 14. Blood supply• Nutrient arteryterminates in the adult metaphysis by anastomosing with epiphysial, metaphysial and periosteal arteries.Supplies medullary cavity , inner 2/3rd of cortex and metaphysis.• Periosteal arteriesEnter the Volkmann’s canals . Supply outer 1/3rd of cortex.25/27/2012 1212413114 14
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  16. 16. • Epiphysial arteriesDerived from periarticular vascular arcades(circulus vasculosus) found on the nonarticula bony surface.• Metaphysial arteriesDerived from the neighbouring systemic vessels.25/27/2012 1212413114 16
  17. 17. Classification• Regional classificationAxial skeleton- 80 bonesAppedicular skeleton-126 bones• Microscopic classificationCompact boneCancellous/trabecular bone25/27/2012 1212413114 17
  18. 18. • Developmental classificationMembranous bones(dermal bone)Cartilaginous bonesMembrano-cartilaginous bones25/27/2012 1212413114 18
  19. 19. • Bone shapesLong bonesShort bonesFlat bonesIrregular bonesSesamoid bonesPneumatic bonesAccessory bones25/27/2012 1212413114 19
  20. 20. Flat bones Sutural bones Irregular bones Long bones Short bones Sesamoid bones25/27/2012 1212413114 20
  21. 21. Microscopic study25/27/2012 1212413114 21
  22. 22. Bone Cells• Osteocytes = mature bone cells In lacunae Connected by canaliculi• Osteoblasts Osteogenesis Contain Alk phosphatase and pyrophosphatase• Osteoclasts Osteolysis• Osteoprogenitor cells differentiate into osteoblasts25/27/2012 1212413114 22
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  24. 24. Compact and Spongy Bone25/27/2012 1212413114 24
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  26. 26. Compact and Spongy Bone• Compact bone located where stresses are limited in direction.• Spongy bone located where stresses are weaker or multi-directional.25/27/2012 1212413114 26
  27. 27. Periosteum and endosteum• PeriosteumSuperficial surface of all bone except in joint cavities.Provide route for blood and nerve supplyParticipate in bone growth and repairOuter fibrous layer and inner cellular layer perforating fibers called as Sharpey’s fibers25/27/2012 1212413114 27
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  29. 29. • EndosteumLines the marrow cavityIncomplete cellular layerWhere layer is incomplete, Osteoblasts and osteoclasts can deposit or remove matrix components.Shallow groove formed by osteoclasts called as Howship’s lacunae25/27/2012 1212413114 29
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  31. 31. Composition of Bone• cellular structures in ground substance• Ground substance made up ofInorganic minerals and organic matrix• Organic matrix(35%)Collagen type 1GlycosaminoglycansProteoglycans, osteonectin and osteocalcin25/27/2012 1212413114 31
  32. 32. • Inorganic content(65%) largely made up of Ca ++ , PO4--- and OH- .• These ions arranged parallel to the direction of collagen fibers by forming a crystalline structure called as Hydroxyapatite . Ca10(Po4)6(OH)2Living bone contain 20% of water25/27/2012 1212413114 32
  33. 33. • Inorganic content give rigidity to the bone• Organic content give the elasticity to the bone.• Lack of inorganic content- soft bone• Lack of organic content- brittle bone25/27/2012 1212413114 33
  34. 34. Intramembranous osteogenesis• Bone formation directly from the mesenchymal sheath( formed by collagen fibers in between the mesenchymal cells)• Not the common process• Also called as dermal ossification because of its presence in deeper layers of dermis.• Roofing bones of skull, clavicle and mandible.25/27/2012 1212413114 34
  35. 35. Intramembranous ossification• Mesenchymal cells condensation• Secretion of organic matrix by the mesenchymal cells which consists of collagen fibers. Thus forming the mesenchymal sheath.• Localized differentiation of osteoblasts with in sheath25/27/2012 1212413114 35
  36. 36. • Bone grows outward from the ossification center in radiating fashion and forms tabeculae.• Trapped osteoblast in between the layer of bone is called as osteocytes.• Blood vessels grows and trapped in between trabeculae.• Initially spongy bone is formed which later changed to the compact bone.25/27/2012 1212413114 36
  37. 37. Endochondral ossification• Most bone formed by this way• Cartilaginous model is replaced(!!) by the bone.• Chondrocyte hypertrophy• Degeneration and calcification• Vascular invasion• ossificaton25/27/2012 1212413114 37
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  40. 40. Growth at epiphysial plate• Zone of resting cells• Zone of proliferating cells• Zone of hypertrophic cells• Zone of calcified cellsIncrease in length25/27/2012 1212413114 40
  41. 41. Appositional growthIncreased in thickness of bone.• Occurs in bony surface.25/27/2012 1212413114 41
  42. 42. • Bone is the dynamic tissue so its composition varies according to the regulating factors.• 99% of body calcium, 80% of phosphorus and 65% of sodium and magnesium is reserved in the bone• Calcium is needed for many physiological function so it is tightly regulated at normal level (9-11mg/dl)25/27/2012 1212413114 42
  43. 43. Factors affecting bone growth• Minerals• Vitamins• Hormones• Exercise25/27/2012 1212413114 43
  44. 44. Clinical Aspects• SubluxationIncomplete or partial displacement of joint• Dislocation / LuxationComplete displacement of joint• FractureLoss of continuity of bone due to abnormal forces or due to weakening of bone.25/27/2012 1212413114 44
  45. 45. • Types of fracturesSimple or ClosedCompound or OpenComminutedGreenstick• Not complete• Common in children.25/27/2012 1212413114 45
  46. 46. Healing of fracture wound25/27/2012 1212413114 46
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  48. 48. Bone disorders• OsteopeniaDecreased in bone mineral density(BMD)• OsteoporosisLoss of both bone salts and collagen content• Osteomalacia/ RicketsLoss of mineral content but not the collagen25/27/2012 1212413114 48
  49. 49. Bone disorders• Paget’s diseaseAbnormal bone remodeling , lead to abnormal thickening of the boneConsequences ???• OsteomyelitisInflammation of bone marrowMost commonly by staphylococcus aureus25/27/2012 1212413114 49
  50. 50. Bone disorders• Osteogenic sarcoma (osteosarcoma)Bone cancer that affects osteoblast25/27/2012 1212413114 50
  51. 51. THANK YOU25/27/2012 1212413114 51
  52. 52. 25/27/2012 1212413114 52

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