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BONE TISSUE

BONE TISSUE. DEVELOPMENT and GROWTH. FUNCTIONS. Support/Movement Protection Mineral reservoir Site of blood cell production Storage of fat. Skeletal Cartilage. Consists primarily of water Contains no nerves or blood vessels Surrounded by perichondrium Dense irregular connective tissue

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BONE TISSUE

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  1. BONE TISSUE DEVELOPMENT and GROWTH

  2. FUNCTIONS • Support/Movement • Protection • Mineral reservoir • Site of blood cell production • Storage of fat

  3. Skeletal Cartilage • Consists primarily of water • Contains no nerves or blood vessels • Surrounded by perichondrium • Dense irregular connective tissue • Maintains shape

  4. Skeletal Cartilage • Basic components • Chondrocytes in lacunae • Extracellular matrix with jellylike ground substance • 3 Types • Hyaline • Elastic • Fibrocartilage

  5. Hyaline Cartilage • Most abundant • Fiber not detectable • Locations • Articular cartilage • Costal cartilage • Respiratory cartilage • Nasal cartilage

  6. Elastic Cartilage • Contains more elastic fibers; more flexible • Found in ear and epiglottis

  7. Fibrocartilage • Highly compressible • Great strength • Locations • Knee • Vertebral disks

  8. Cartilage Growth • Two methods • Appositional – adds to outside • Interstitial – growth from inside • Growth stops during adolescence

  9. Bone Histology - Cell Types • Osteocytes – mature bone cells • Osteoblasts – bone forming cells • Osteoclasts – bone destroyers

  10. BONE OSSIFICATION Process by which tissue becomes bone Also called osteogenesis

  11. Bone Formation • Bone formation begins approx. 8 weeks into fetal development from a skeleton that is mostly fibrous membranes and cartilage • Intramembranous ossification – bone forms from the fibrous membranes • Endochondral ossification – bone forms from hyaline cartilage

  12. Intramembranous Ossification • Osteoprogenitor (mesenchymal) cells in fibrous C.T. develop into osteoblasts • Osteoblasts secrete collagen matrix • Calcification occurs in ossification centers; forming a network of bone rather than layers • Bony plates form which are later converted into compact bone • Flat bones only; skull & clavicles • Fontanelles are areas not ossified at birth

  13. ENDOCHONDRAL OSSIFICATION • Forms most bones • Hyaline cartilage model in shape of the bone initially; a pH change causes cartilage to calcify and the cells to die • Primary ossification center forms as blood vessels from periosteum and osteoblasts invade calcified cartilage • Matrix formed (osteoid= unmineralized bone matrix) • Ossification occurs = calcium salts deposited • Primary centers form before birth; Secondary centers form 8th month dev.

  14. Epiphyseal Plate • Cartilage region between primary and secondary ossification centers • Responsible for postnatal bone growth • Zone of resting cartilage • Growth Zone – mitosis occurs • Transformation Zone – cartilage matrix deteriorates • Osteogenic Zone - bone salts deposited

  15. Calcium regulation • Calcium is most abundant mineral in the body; 99% located in the bone • Regulated by two hormones: PTH (parathyroid hormone) and calcitonin • PTH - raises blood calcium levels • Calcitonin - lowers blood calcium levels

  16. Hormones and Vitamin Effect on Bone Growth • Testosterone • Estrogen • Growth Hormone • Throxine - • Vitamin D – calcium absorption

  17. Compact Bone also called dense bone hard, strong and solid bone that forms the outer layer of all bone provides support, protection and resists stress Contains osteons Cancellous also called spongy bone found more toward the inner portion of bone open lattice-work of struts and plates that serves to store bone marrow Trabeculae Bone Types

  18. Haversian canal Volkmann’s canals Lamellae Lacunae Canaliculi Osteons = Haversian System

  19. Bone Types • Long – arms and legs • Short – wrist and ankle • Sesamoid – forms within a tendon (patella) • Flat – sternum, scapula, ribs, skull • Irregular – vertebrae & coxal bones

  20. Structure of a Long Bone • Diaphysis • Epiphysis • Articular cartilage • Periosteum – connective tissue covering bone • Medullary cavity • Endosteum – connective tissue; lines inside

  21. Bone Fractures • Open ( Compound) – penetrates skin • Closed (Simple) • Partial/Complete - Greenstick • Comminuted – broken into 3 or more pieces

  22. Bone Repair • Formation of clot ( hematoma) • Callus ( soft followed by hard) • Mineralization of callus by calcium & phosphorus • Remodeling

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