Bone histology amir


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Bone histology amir

  1. 1. Bone TissueBone Tissue Alam Zeb AmirAlam Zeb Amir
  2. 2.  Objectives:Objectives:  Identify main functions of osseous tissueIdentify main functions of osseous tissue  Identify the major parts of a longIdentify the major parts of a long  Describe the cells found in osseous tissueDescribe the cells found in osseous tissue  Describe the components of an osteonDescribe the components of an osteon  Compare and contrast intramembranousCompare and contrast intramembranous and endochondral ossification.and endochondral ossification.
  3. 3.  Osteology: study of osseous structures.Osteology: study of osseous structures. SupportSupport ProtectionProtection MovementMovement Mineral homeostasisMineral homeostasis Hemopoiesis: blood cell formationHemopoiesis: blood cell formation Storage of adipose tissue: yellow marrowStorage of adipose tissue: yellow marrow
  4. 4. Long bone anatomyLong bone anatomy  Diaphysis: long shaft of boneDiaphysis: long shaft of bone  Epiphysis: ends of boneEpiphysis: ends of bone  Epiphyseal plate: growth plateEpiphyseal plate: growth plate  Metaphysis: b/w epiphysis and diaphysisMetaphysis: b/w epiphysis and diaphysis  Articular cartilage: covers epiphysisArticular cartilage: covers epiphysis  Periosteum: bone covering (pain sensitive)Periosteum: bone covering (pain sensitive)  Sharpey’s fibers: periosteum attaches toSharpey’s fibers: periosteum attaches to underlying boneunderlying bone  Medullary cavity: Hollow chamber in boneMedullary cavity: Hollow chamber in bone - red marrow produces blood cells- red marrow produces blood cells - yellow marrow is adipose.- yellow marrow is adipose.  Endosteum: thin layer lining theEndosteum: thin layer lining the medullary cavitymedullary cavity
  5. 5. Long boneLong bone
  6. 6. DiaphysisDiaphysis
  7. 7. EpiphysisEpiphysis
  8. 8. MetaphysisMetaphysis
  9. 9. Epiphyseal (growth) plateEpiphyseal (growth) plate
  10. 10. Medullary cavityMedullary cavity
  11. 11.  Histology of bone tissueHistology of bone tissue Cells are surrounded by matrix.Cells are surrounded by matrix. - 25% water- 25% water - 25% protein- 25% protein - 50% mineral salts- 50% mineral salts 4 cell types make up osseous tissue4 cell types make up osseous tissue Osteoprogenitor cellsOsteoprogenitor cells OsteoblastsOsteoblasts OsteocytesOsteocytes OsteoclastsOsteoclasts
  12. 12.  Osteoprogenitor cells:Osteoprogenitor cells: - derived from mesenchyme- derived from mesenchyme - all connective tissue is derived- all connective tissue is derived - unspecialized stem cells- unspecialized stem cells - undergo mitosis and develop into- undergo mitosis and develop into osteoblastsosteoblasts - found on inner surface of periosteum- found on inner surface of periosteum and endosteum.and endosteum.
  13. 13.  Osteoblasts:Osteoblasts: - bone forming cells- bone forming cells - found on surface of bone- found on surface of bone - no ability to mitotically divide- no ability to mitotically divide - collagen secretors- collagen secretors  Osteocytes:Osteocytes: - mature bone cells- mature bone cells - derived form osteoblasts- derived form osteoblasts - do not secrete matrix material- do not secrete matrix material - cellular duties include exchange of- cellular duties include exchange of nutrientsnutrients and waste with blood.and waste with blood.
  14. 14. OsteocyteOsteocyte
  15. 15.  OsteoclastsOsteoclasts - bone resorbing cells- bone resorbing cells - bone surface- bone surface - growth, maintenance and bone repair- growth, maintenance and bone repair Abundant inorganic mineral salts:Abundant inorganic mineral salts: - Tricalcium phosphate in crystalline form called- Tricalcium phosphate in crystalline form called hydroxyapatitehydroxyapatite CaCa33(PO(PO44))22(OH)(OH)22 - Calcium Carbonate: CaCOCalcium Carbonate: CaCO33 - Magnesium Hydroxide: Mg(OH)Magnesium Hydroxide: Mg(OH)22 - Fluoride and SulfateFluoride and Sulfate
  16. 16. These salts are deposited on the collagenThese salts are deposited on the collagen fiber framework (tensile strength) andfiber framework (tensile strength) and crystallization occurs.crystallization occurs. - calcification or mineralization- calcification or mineralization
  17. 17.  Compact bone: (Osteon) external layerCompact bone: (Osteon) external layer - called lamellar bone (groups of- called lamellar bone (groups of elongated tubules called lamella)elongated tubules called lamella) - majority of all long bones- majority of all long bones - protection and strength (wt. bearing)- protection and strength (wt. bearing) - concentric ring structure- concentric ring structure - blood vessels and nerves penetrate- blood vessels and nerves penetrate periosteum through horizontalperiosteum through horizontal openings called perforatingopenings called perforating (Volkmann’s)(Volkmann’s) canals.canals.
  18. 18. - central (Haversian) canals run- central (Haversian) canals run longitudinally. Blood vessels andlongitudinally. Blood vessels and nerves.nerves. - around canals are concentric lamella- around canals are concentric lamella - osteocytes occupy lacunae (“little lakes”)- osteocytes occupy lacunae (“little lakes”) which are between the lamellawhich are between the lamella - radiating from the lacunea are channels- radiating from the lacunea are channels called canaliculi. (finger like processescalled canaliculi. (finger like processes of osteocytes)of osteocytes)
  19. 19. - Lacunae are connected to one another byLacunae are connected to one another by canaliculi.canaliculi. - Osteon contains: - central canalOsteon contains: - central canal - surrounding lamellae- surrounding lamellae - lacunae- lacunae - osteocytes- osteocytes - canaliculi- canaliculi
  20. 20. Compact boneCompact bone
  21. 21.  Spongy bone (cancellous bone): internalSpongy bone (cancellous bone): internal layerlayer - latticework of bone tissue (haphazard- latticework of bone tissue (haphazard arrangement).arrangement). - made of trabeculae (“little beams”)- made of trabeculae (“little beams”) - filled with red and yellow bone marrow- filled with red and yellow bone marrow - osteocytes get nutrients directly from- osteocytes get nutrients directly from circulating blood.circulating blood. - short, flat and irregular bone is made up- short, flat and irregular bone is made up of mostly spongy boneof mostly spongy bone
  22. 22. Cancellous (spongy) boneCancellous (spongy) bone
  23. 23.  Bone formation (ossification) occurs in two waysBone formation (ossification) occurs in two ways 1- Intramembranous ossification1- Intramembranous ossification 2- Endochondral ossification2- Endochondral ossification Both methods above lead to the same boneBoth methods above lead to the same bone formation but are different methods of gettingformation but are different methods of getting there.there. Ossification (osteogenesis) begins around the 6Ossification (osteogenesis) begins around the 6thth -7-7thth week of embryonic life. At this time the embryonicweek of embryonic life. At this time the embryonic skeleton is made of fibrous membranes andskeleton is made of fibrous membranes and hyaline cartilage.hyaline cartilage.
  24. 24. Hyaline Cartilage ReviewHyaline Cartilage Review a. Most abundanta. Most abundant b. Provides support, flexibility andb. Provides support, flexibility and resilienceresilience c.   Located:c.   Located: a. forming nearly all the fetal skeletona. forming nearly all the fetal skeleton b.b. articular cartilagearticular cartilage: ends of moving: ends of moving bonesbones c.c. costal cartilagecostal cartilage: ribs to sternum: ribs to sternum d. tip of nosed. tip of nose e. respiratory cartilagee. respiratory cartilage
  25. 25.  Skeletal Cartilage:Skeletal Cartilage: 1.1. Chondrocytes: cartilage producingChondrocytes: cartilage producing cells.cells. 2.      Lacunae: small cavities where the2.      Lacunae: small cavities where the chondrocytes are encased.chondrocytes are encased. 3.      Extracellular matrix: jellylike ground3.      Extracellular matrix: jellylike ground substance.substance. 4.      Perichondrium: layer of dense4.      Perichondrium: layer of dense irregular connective tissue thatirregular connective tissue that surroundssurrounds the cartilage.the cartilage. 5.      No blood vessels or nerves5.      No blood vessels or nerves
  26. 26.  IntramembranousIntramembranous (within the membrane)(within the membrane) ossification: Bone develops from a fibrousossification: Bone develops from a fibrous membrane.membrane. - flat bones of skull- flat bones of skull - mandible- mandible - clavicles- clavicles -mesenchymal cells become vascularized and-mesenchymal cells become vascularized and become osteoprogenitor cells and thenbecome osteoprogenitor cells and then osteoblasts.osteoblasts. - organic matrix of bone is secreted- organic matrix of bone is secreted - osteocytes are formed- osteocytes are formed - calcium and mineral salts are deposited and- calcium and mineral salts are deposited and bone tissue hardens.bone tissue hardens. - trabeculae develop and spongy bone is formed- trabeculae develop and spongy bone is formed - red marrow fills spaces- red marrow fills spaces
  27. 27. Replacement of hyaline cartilage with bone is calledReplacement of hyaline cartilage with bone is called .. Endochondral (intracartilaginous) ossificationEndochondral (intracartilaginous) ossification Most bones are formed this way (i.e. long bones).Most bones are formed this way (i.e. long bones). Where bone is going to form:Where bone is going to form: 1- mesenchymal cells differentiate into1- mesenchymal cells differentiate into chondroblasts (immature cartilage cells) whichchondroblasts (immature cartilage cells) which produces hyaline cartilage.produces hyaline cartilage. Perichondrium develop around new cartilagePerichondrium develop around new cartilage 2- Chondrocytes (mature) mitotically divide increasing2- Chondrocytes (mature) mitotically divide increasing in lengthin length This pattern of growth:This pattern of growth: interstitial growth.interstitial growth.
  28. 28. Growth of cartilage inGrowth of cartilage in thicknessthickness occurs fromoccurs from the deposition of new matrix to thethe deposition of new matrix to the periphery formed by chondroblasts withinperiphery formed by chondroblasts within the perichondrium.the perichondrium. Appositional growthAppositional growth.. Chondrocytes undergo hypertrophy, swellChondrocytes undergo hypertrophy, swell and burst. pH of the matrix changes andand burst. pH of the matrix changes and calcification is triggered. Ultimately,calcification is triggered. Ultimately, cartilage cells die. Lacunae are nowcartilage cells die. Lacunae are now empty.empty.
  29. 29. Nutrients are supplied by way of the nutrientNutrients are supplied by way of the nutrient artery passing through the perichondriumartery passing through the perichondrium through the nutrient foramen.through the nutrient foramen. Osteoprogenitor cells are stimulated in theOsteoprogenitor cells are stimulated in the perichondrium to produce osteoblasts.perichondrium to produce osteoblasts. A thin layer of compact bone is laid downA thin layer of compact bone is laid down under the perichondrium called theunder the perichondrium called the periosteal bone collar.periosteal bone collar. Perichondrium becomes periosteumPerichondrium becomes periosteum
  30. 30. Osteoblasts begin to deposit bone matrixOsteoblasts begin to deposit bone matrix forming spongy bone trabeculae.forming spongy bone trabeculae. In the middle of the bone, osteoclasts breakIn the middle of the bone, osteoclasts break down spongy bone trabeculae and form adown spongy bone trabeculae and form a hollowed out cavity called the medullaryhollowed out cavity called the medullary cavity. This cavity will be filled with redcavity. This cavity will be filled with red bone marrow for hemopoiesis.bone marrow for hemopoiesis. The shaft of the bone is replaced (wasThe shaft of the bone is replaced (was hyaline cartilage) with compact bone.hyaline cartilage) with compact bone.
  31. 31.  Physiology of bone growth:Physiology of bone growth: - epiphyseal plate (bone length)- epiphyseal plate (bone length) - 4 zones of bone growth under hGH.- 4 zones of bone growth under hGH. 1- Zone of resting cartilage:1- Zone of resting cartilage: - no bone growth- no bone growth - located near the epiphyseal plate- located near the epiphyseal plate - scattered chondrocytes- scattered chondrocytes - anchors plate to bone- anchors plate to bone 2- Zone of proliferating cartilage2- Zone of proliferating cartilage - chondrocytes stacked like coins- chondrocytes stacked like coins - chondrocytes divide- chondrocytes divide
  32. 32. 3- Zone of hypertrophic (maturing) cartilage3- Zone of hypertrophic (maturing) cartilage - large chondrocytes arranged in columns- large chondrocytes arranged in columns - lengthwise expansion of epiphyseal plate- lengthwise expansion of epiphyseal plate 4- Zone of calcified cartilage4- Zone of calcified cartilage - few cell layers thick- few cell layers thick - occupied by osteoblasts and osteoclasts- occupied by osteoblasts and osteoclasts and capillaries from the diaphysisand capillaries from the diaphysis - cells lay down bone- cells lay down bone - dead chondrocytes surrounded by a calcified- dead chondrocytes surrounded by a calcified matrix. Matrix resembles long spicules ofmatrix. Matrix resembles long spicules of calcifiedcalcified cartilage. Spicules are partly eroded bycartilage. Spicules are partly eroded by osteoclastsosteoclasts and then covered in bone matrixand then covered in bone matrix from osteoblasts:from osteoblasts: spongy bone is formed.spongy bone is formed.
  33. 33. Age 18-21: Longitudinal bone growth ends whenAge 18-21: Longitudinal bone growth ends when epiphysis fuses with the diaphysis.epiphysis fuses with the diaphysis. - epiphyseal plate closure- epiphyseal plate closure - epiphyseal line is remnant of this- epiphyseal line is remnant of this - last bone to stop growing: clavicle- last bone to stop growing: clavicle
  34. 34.  Bone width: increase in diameter of boneBone width: increase in diameter of bone occurs through appositional growth .occurs through appositional growth . - Osteoblasts located beneath the- Osteoblasts located beneath the periosteum secrete bone matrix and buildperiosteum secrete bone matrix and build bone on the surfacebone on the surface - Osteoclasts located in the endosteum- Osteoclasts located in the endosteum resorbs (breakdown) bone.resorbs (breakdown) bone.
  35. 35.  Bone Remodeling:Bone Remodeling: - bone continually renews itself- bone continually renews itself - never metabolically at rest- never metabolically at rest - enables Ca to be pulled from bone when- enables Ca to be pulled from bone when blood levels are lowblood levels are low - osteoclasts are responsible for matrix- osteoclasts are responsible for matrix destructiondestruction - produce lysosomal enzymes and acids- produce lysosomal enzymes and acids - spongy bone replaced every 3-4 years- spongy bone replaced every 3-4 years - compact bone every 10 years- compact bone every 10 years
  36. 36. - Blood calcium levels signal release of either- Blood calcium levels signal release of either parathyroid hormoneparathyroid hormone (PTH, secreted by(PTH, secreted by parathyroid gland) andparathyroid gland) and calcitonincalcitonin (secreted(secreted by thyroid).by thyroid). PTH causes calcium release from bone matrixPTH causes calcium release from bone matrix byby stimulating osteoclast activity and bonestimulating osteoclast activity and bone resorption.resorption. Calcitonin inhibits bone resorption and causesCalcitonin inhibits bone resorption and causes calcium salts to be deposited in bone matrix.calcium salts to be deposited in bone matrix. Vitamins A, C, D and BVitamins A, C, D and B1212 help in bone remodelinghelp in bone remodeling
  37. 37.  Fractures: Any bone break.Fractures: Any bone break. - blood clot will form around break- blood clot will form around break - fracture hematoma- fracture hematoma - inflammatory process begins- inflammatory process begins - blood capillaries grow into clot- blood capillaries grow into clot - phagocytes and osteoclasts remove- phagocytes and osteoclasts remove damaged tissuedamaged tissue - procallus forms and is invaded by- procallus forms and is invaded by osteoprogenitor cells and fibroblastsosteoprogenitor cells and fibroblasts - collagen and fibrocartilage turns- collagen and fibrocartilage turns procallus to fibrocartilagenous (soft) callusprocallus to fibrocartilagenous (soft) callus
  38. 38. - broken ends of bone are bridged by callusbroken ends of bone are bridged by callus - Osteoprogenitor cells are replaced byOsteoprogenitor cells are replaced by osteoblasts and spongy bone is formedosteoblasts and spongy bone is formed - bony (hard) callus is formedbony (hard) callus is formed - callus is resorbed by osteoclasts and compactcallus is resorbed by osteoclasts and compact bone replaces spongy bone.bone replaces spongy bone. Remodeling : the shaft is reconstructed toRemodeling : the shaft is reconstructed to resemble original unbroken bone.resemble original unbroken bone. Closed reduction - bone ends coaxed back intoClosed reduction - bone ends coaxed back into place by manipulationplace by manipulation Open reduction - surgery, bone ends securedOpen reduction - surgery, bone ends secured together with pins or wirestogether with pins or wires
  39. 39.  Simple/Closed: bone breaks cleanly, butSimple/Closed: bone breaks cleanly, but doesdoes not penetrate skinnot penetrate skin  Compound/Open: broken ends of boneCompound/Open: broken ends of bone protrude through tissue and skinprotrude through tissue and skin  Comminuted bone fragments into manyComminuted bone fragments into many piecespieces  Compression: bone is crushed ( due toCompression: bone is crushed ( due to porous bone)porous bone)  Depressed: broken bone is pressed inwardDepressed: broken bone is pressed inward (e.g. in skull)(e.g. in skull)  Colles’: posterior displacement of distal endColles’: posterior displacement of distal end
  40. 40.  Smith’s: anterior displacement of distalSmith’s: anterior displacement of distal endend of radius (flexion)of radius (flexion)  Transverse: break occurs across the longTransverse: break occurs across the long axisaxis of a boneof a bone  Impacted: broken bone ends are forcedImpacted: broken bone ends are forced intointo each othereach other  Spiral: ragged break as a result ofSpiral: ragged break as a result of excessive twisting of boneexcessive twisting of bone  Epiphyseal: break occurring alongEpiphyseal: break occurring along epiphyseal line/plateepiphyseal line/plate  Greenstick: bone breaks incompletelyGreenstick: bone breaks incompletely  Pott's: malleolus of tibia and fibula breakPott's: malleolus of tibia and fibula break
  41. 41. GaleazziGaleazzi Fx.Fx.
  42. 42. MonteggiaMonteggia
  43. 43. Pott’s FxPott’s Fx
  44. 44. Colles’ Fx.Colles’ Fx.