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Biol121 chp6-pp-fall10-101022213400-phpapp02
- 1. 1 The Skeletal System: Bone Tissue BIOL 121: A&P IChapter 6 Rob Swatski Associate Professor of Biology HACC – York CampusTextbook images - Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
- 2. 2
- 3. 3 Skeletal System Tissues Bone Cartilage Dense CT Epithelium Adipose Nervous
- 4. 4
- 5. 5 Functions of Bone Supports body Protects soft tissues Muscle attachment site
- 6. 6 Functions of Bone, cont. Mineral storage & homeostasis Produces blood cells in red bone marrow (hemopoiesis aka hematopoiesis) Energy storage in yellow bone marrow
- 8. 8
- 9. 9 Anatomy of a Long Bone
- 10. 10 Anatomy of a Long Bone Diaphysis Epiphysis Metaphysis Epiphyseal plate Articular cartilage
- 11. (b) Partially sectioned humerus Medullary cavity in diaphysis Compact bone Spongy bone Epiphyseal line Proximal epiphysis Metaphysis
- 12. 12 Anatomy of a Long Bone, cont. Medullary (Marrow) cavity Endosteum Periosteum: 2 layers A. Fibrous layer B. Osteogenic layer
- 13. 13
- 14. 14
- 15. 15 Histology of Bone Tissue Compact bone Spongy bone Specialized bone cells Extracellular matrix
- 16. 16
- 17. 17 Matrix 15% water, 30% collagen, 55% mineral salts Calcium phosphate (hydroxyapatite), calcium carbonate, K, Mg Collagen fiber skeleton = tensile strength Calcification (Mineralization) = hardness
- 18. 18
- 19. 19 4 Types of Bone Cells Osteogenic cells Osteoblasts Osteocytes Osteoclasts
- 20. 20 Osteogenic Cells = Osteoprogenitor cells Undifferentiated Found in periosteum & endosteum Develop into osteoblasts
- 21. 21 Osteoblasts Bone-building cells Do not divide Form bone matrix & secrete collagen fibers Develop into osteocytes
- 22. 22 Osteocytes Mature bone cells; do not divide Maintain bone tissue No longer secrete matrix
- 23. 23
- 24. 24 Osteoclasts Largest of the bone cells Originate from fused monocytes (WBC’s) Bone resorption
- 25. 25
- 26. 26 Compact (Dense) Bone Solid, hard, external layer of bone Forms diaphysis of long bones Resists stresses of weight & movement Arranged in units called osteons
- 27. 27 Osteons aka Haversian systems House the osteocytes Abundant vascular tissue: blood vessels & lymphatics Well-innervated with nervous tissue
- 28. (a) Osteons (Haversian systems) in compact bone and trabeculae in spongy bone Compact bone Spongy bone Periosteum Medullary cavity Outer circumferential lamellae Interstitial lamellae Concentric lamellae Blood vessels Canaliculi Osteocyte Lacuna Periosteal vein Periosteal artery Periosteum: Outer fibrous layer Inner osteogenic layer Central canal Compact bone Spongy bone Inner circumferential lamellae Trabeculae Medullary cavity See Figure 6.3b for details Perforating canal Perforating (Sharpey’s) fibers Osteon
- 29. 29 Osteon Histology Concentric lamellae of matrix around central canal Osteocytes inside lacunae Canaliculi Interstitial lamellae
- 30. 30
- 31. 31
- 32. 32 Spongy Bone No osteons Consists of trabeculae Supports red bone marrow Reduces weight Short, flat, irregular bones Epiphyses of long bones
- 33. 33
- 35. 35 Bone Formation (Ossification) Embryonic CT begins as mesenchyme Template for ossification Intramembranous ossification Endochondral ossification
- 36. 36
- 37. 37 Intramembranous Ossification Forms flat & irregular bones of skull & mandible “Jelly sandwich” Mesenchyme Osteogenic cells Ossification center Osteoblasts Matrix (Calcification) Osteoblasts Osteocytes Osteogenic cells
- 38. 38
- 39. 39Osteoblasts
- 40. 40 Intramembranous Ossification, cont. Calcifying matrix joins to form trabeculae Spongy bone forms around red bone marrow Surface mesenchyme Periosteum Superficial spongy bone Compact bone
- 41. 41
- 42. Flat bone of skull Mandible Blood capillary Ossification center Mesenchyme Osteoblast Collagen fiber Development of ossification center: osteoblasts secrete organic extracellular matrix 1 Osteocyte in lacuna Calcification: calcium and other mineral salts are deposited and extracellular matrix calcifies (hardens) 2 Canaliculus Osteoblast Newly calcified bone extracellular matrix Mesenchyme condenses Formation of trabeculae: extracellular matrix develops into trabeculae that fuse to form spongy bone 3 Blood vessel Spongy bone trabeculae Osteoblast Periosteum Compact bone tissue Spongy bone tissue Compact bone tissue Development of the periosteum: mesenchyme at the periphery of the bone develops into the periosteum 4
- 43. 43 Endochondral Ossification Forms long bones Replaces cartilage with bone Six step process Begins with formation of cartilage model
- 44. 44 1. Development of Cartilage Model Originates from mesenchyme Basic shape & length of bone Hyaline cartilage & chondroblasts Perichondrium
- 45. 45 2. Growth of Cartilage Model Chondrocytes divide & matrix forms Interstitial growth Appositional growth Mid-region cells burst & lower pH Destroys chondrocytes & triggers calcification
- 46. 46 3. Development of Primary Ossification Center Perichondrium Periosteum Forms periosteal bone collar Nutrient artery penetrates center of bone model Periosteal bud brings osteoblasts & osteoclasts to center
- 47. 47
- 48. 48 4. Development of Medullary Cavity Osteoblasts deposit matrix over calcified cartilage Form trabeculae of spongy bone Osteoclasts form medullary cavity
- 49. 49 5. Development of Secondary Ossification Center Blood vessels enter uncalcified epiphyses Spongy bone develops
- 50. 50 6. Formation of Articular Cartilage & Epiphyseal Plate Epiphyseal cartilage does not ossify Remains as articular cartilage Epiphyseal (Growth) plate also remains as cartilage Source of interstitial growth
- 51. Development of cartilage model: mesenchymal cells develop into chondroblasts, which form the cartilage model. 1 Proximal epiphysis Diaphysis Distal epiphysis Hyaline cartilage Perichondrium Endochondral Ossification - Overview Growth of cartilage model: growth occurs by cell division of chondrocytes. 2 Uncalcified extracellular matrix Calcified extracellular matrix Nutrient artery Periosteum Primary ossification center Spongy bone Development of primary ossification center: in this region of the diaphysis, bone tissue replaces most of the cartilage. 3
- 52. Uncalcified extracellular matrix Development of the medullary (marrow) cavity: bone breakdown by osteoclasts forms the medullary cavity. 4 Calcified extracellular matrix Periosteum Medullary cavity Nutrient artery and vein Development of secondary ossification centers: these occur in the epiphyses of the bone. 5 Secondary ossification center Uncalcified extracellular matrix Epiphyseal artery and vein Articular cartilage Spongy bone Epiphyseal plate Formation of articular cartilage and epiphyseal plate: both structures consist of hyaline cartilage. 6 Endochondral Ossification – Overview, cont.
- 53. (b) Twelve-week fetus. The red areas represent bones that are forming (calcified). Clear areas represent cartilage (uncalcified).
- 54. 54 Epiphyseal (Growth) Plate Chondrocytes produce cartilage on epiphyseal side Cartilage replaced by bone on diaphyseal side Plate closes at age 18-25 Chondrocytes stop dividing Bone replaces cartilage (epiphyseal line)
- 55. 55 4 Zones of Epiphyseal Plate Zone of Resting Cartilage Zone of Proliferating Cartilage Zone of Hypertrophic Cartilage Zone of Calcified Cartilage
- 56. Epiphysis (c) Lengthwise growth of bone at epiphyseal plate EPIPHYSEAL (GROWTH) PLATE: Zone of resting cartilage Zone of proliferating cartilage Zone of hypertrophic cartilage Zone of calcified cartilage Diaphysis Articular cartilage New chondrocytes are formed Old chondrocytes are replaced by bone New diaphysi s
- 57. 57 Zone of Resting Cartilage Anchors growth plate to bone
- 58. 58 Zone of Proliferating Cartilage Rapid cell division (stacks of coins)
- 59. 59 Zone of Hypertrophic Cartilage Cells enlarge & remain in columns
- 60. 60 Zone of Calcified Cartilage Thin zone – mostly dead cells Osteoblasts & osteoclasts active
- 62. Ridges in periosteum create groove for periosteal blood vessel. 1 Periosteal ridges Periosteum Periosteal blood vessel Perforating canal Groove Periosteal ridges fuse, forming an endosteum-lined tunnel. 2 Endosteum Tunnel Osteoblasts in endosteum build new concentric lamellae inward toward center of tunnel, forming a new osteon. 3 Endosteum Bone grows outward as osteoblasts in periosteum build new circumferential lamellae. Osteon formation repeats as new periosteal ridges fold over blood vessels. 4 Circumferential lamellae Periosteum New osteon Central (haversian) canal
- 63. Ridges in periosteum create groove for periosteal blood vessel. 1 Periosteal ridges Periosteum Periosteal blood vessel Perforating canal Groove
- 64. Periosteal ridges fuse, forming an endosteum-lined tunnel. 2 Endosteum Tunnel
- 65. Osteoblasts in endosteum build new concentric lamellae inward toward center of tunnel, forming a new osteon. 3 Endosteum
- 66. Bone grows outward as osteoblasts in periosteum build new circumferential lamellae. Osteon formation repeats as new periosteal ridges fold over blood vessels. 4 Circumferential lamellae Periosteum New osteon Central (haversian) canal
- 67. Medullary cavity Bone formed by osteoblasts Bone destroyed by osteoclasts Infant Child Young adult Adult (b) Macroscopic changes
- 68. 68 Factors Affecting Bone Growth: Nutrition Calcium & Phosphorus Vitamin C collagen Vitamins K & B12 protein synthesis
- 69. 69 Factors Affecting Bone Growth: Hormones Insulinlike Growth Factors (IGFs) Thyroid hormone, Human Growth Hormone (hGH), insulin Estrogen & testosterone
- 71. 71 Orthodontics
- 75. Humerus Impacted
- 81. Copyright © 2014 John Wiley & Sons, Inc. All rights reserved. Periosteum Fracture hematoma Fibrocartilaginous callus (soft) Reactive phase: formation of fracture hematoma 1 Reparative phase: fibrocartilaginous callus formation 2a Reparative phase: bony callus formation 2b Bone remodeling phase 3 New blood vessel Spongy bone trabeculae Bony (hard) callus Healed fracture
- 82. 82 1. Reactive Phase: Formation of fracture hematoma (clot)
- 83. 83 2. Reparative Phase: Fibrocartilaginous callus formation
- 84. 84 3. Reparative Phase: Bony callus formation
- 85. 85 4. Bone Remodeling Phase
- 86. 86 Calcium Homeostasis & Bone Tissue Skeleton = Calcium reservoir Nerve & muscle fiber function Blood clotting cascade Enzyme function 9-11 mg Ca+2/100 ml plasma
- 87. 87 Hormonal Regulation of Ca+2 Parathyroid Hormone (PTH) (from parathyroid gland) Calcitriol (from kidneys) Calcitonin (from thyroid gland)
- 88. STIMULUS CONTROLLED CONDITION Blood calcium (Ca2+) level RECEPTORS CONTROL CENTER Parathyroid hormone gene EFFECTORS RESPONSE Increase in blood Ca2+ level Osteoclasts increase bone resorption Kidneys retain Ca2+ in blood, excrete phosphate in urine, and produce calcitriol Parathyroid gland cells Return to homeostasis when response brings blood Ca2+ level back to normal Disrupts homeostasis by decreasing Detect lowered Ca2+ concentration which increases production of cyclic AMP Input Output Gene “turned on” which increases release of PTH Osteoclasts Kidneys
- 89. 89 How do they do this?
- 90. 90 Aging & Bone Tissue Demineralization Osteoporosis Reduced protein synthesis Less collagen Fewer growth hormones
- 91. 91
- 92. 92The End