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Lecture5 cartilage& bone


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Lecture5 cartilage& bone

  1. 1. Cartilage Bone
  2. 2. PRINCIPAL FUNCTIONS OF CARTILAGE supporting soft tissues covering the surfaces of bones forming the bone joints (shock absorber and sliding area) development and growth of long bones
  3. 3. Chondrocytes Extracellular matrix GROUND SUBSTANCE FIBERS Glicosaminoglicans (GAG) collagen fibers Proteoglicans elastic fibers hyaluronic acid
  4. 4. PERICHONDRIUM The capsule of connective tissue covering the cartilage outer layer - dense connective tissue collagen type I fibroblasts the source of nutrients for avascular cartilage inner layer chondroblasts - precursors of chondrocytes
  5. 5. TYPES OF CARTILAGE Hyaline cartilage the most common form contains mainly collagen type II fibers Elastic cartilage many elastic fibers near the collagen type II more pliable than hyaline cartilage Fibrocartilage dense network type I collagen fibers present in regions subject to great mechanical stress
  6. 6. HYALINE CARTILAGE articular surfaces of bones forming movable joints the walls of big respiratory passages larynx, trachea, bigger bronchi epiphyseal plates of long bones the cartilaginous parts of ribs covered by perichondrium (except articular cartilage)
  7. 7. HYALINE CARTILAGE CHONDROCYTES develop from chondroblasts - cells present in the inner layer of the perichondrium at the periphery - elliptic shape farther in - become round , form isogenous groups isogenous group - develops by mitosis of single chondrocyte (5-8 cells in group) produce all components of extracellular matrix well developed RER, Golgi complex
  8. 8. HYALINE CARTILAGE EXTRACELLULAR MATRIX collagen type II fibrils embedded in ground substance ground substance : proteoglicans chondroitin sulfate, keratan sulfate long chains of hyaluronic acid chondronectin - glycoprotein providing adherence of collagen and chondrocytes water bound to the negative charges of glicosaminoglicans
  9. 9. Territorial matrix surrounds each chondrocyte of isogenous group rich in proteoglicans poor in collagen fibrils Interterritorial matrix occurs between isogenous groups numerous collagen type II fibrils Characteristics firm, resistant to compression
  10. 10. ELASTIC CARTILAGE auricle of the ear the wall of external auditory canals auditory tubes (Eustachian tubes ) epiglottis Presence of perichondrium
  11. 11. ELASTIC CARTILAGE Chondrocytes similar to cells of hyaline cartilage smaller isogenous groups ( 2- 3 cells) Extracellular matrix abundant network of elastic fibers collagen type II fibrils ground substance : the same components like in hyaline cartilage
  12. 12. FIBROCARTILAGE annulus fibrosus of intervertebral disc symphysis pubis attachments of ligaments Great resistance to extention
  13. 13. FIBROCARTILAGE Chondrocytes identical to cells of hyaline cartilage single or in groups groups - long raws of chondrocytes Extracellular matrix ground substance - less abundant numerous collagen type I fibers - bundles collagen bundles: parallel to raws of cells visible in light microscope
  14. 14. BONE Specific type of connective tissue with calcified extracellular substance Functions supporting soft tissues protection of important organs CNS in skull thoracic contents in chest reservoir of calcium
  15. 15. OSTEOBLASTS form a layer which resembles the simple epithelium on the surface of bone surround themselves with matrix and become ostecytes basophilic cytoplasm abundant RER, well developed Golgi complex Functions: synthesize the organic components of matrix responsible for calcification of bone matrix play certain role in bone resorption
  16. 16. OSTEOCYTES develop from osteoblasts which surrounded themselves with matrix are located in matrix lacunae (one cell per lacuna) contact to each other by mean of cytoplasmic processes existing in canaliculi of matrix surrounded by thin layer of noncalcified matrix less RER, smaller Golgi complex condensed nuclear chromatin Function: maintenance of the matrix
  18. 18. OSTEOCLASTS large, multinuclear cells derive from monocytes (belong to phagocyte system) ruffled border - surface facing bone ruffled clear zone - adhesion the cell to the matrix acidophilc cytoplasm abundant RER and Golgi complex numerous mitochondria and lisosomes Functions: bone resorption bone growth and bone remodeling
  20. 20. BONE EXTRACELLULAR MATRIX Organic components ( 30-35% of bone weight) collagen type I fibers ( 90%) noncollagenous proteins : osteonectin, osteocalcin, sialoproteins, phosphoproteins, proteolipids proteoglicans Inorganic components ( 70% of bone weight) calcium phosphate - hydroxyapatyte crystals
  21. 21. Periosteum Layer of connective tissue covering the bone Outer layer - dense connective tissue fibroblasts numerous collagen fibers rich in blood vessels (source of vessels for bone) Inner layer osteoprogenitor cells (reservoir of osteoblasts)
  22. 22. Endosteum Thin layer of connective tissue with osteoprogenitor cells Lines internal surfaces of the bone
  23. 23. Types of bone IMMATURE BONE = PRIMARY BONE = = woven bone MATURE BONE = SECUNDARY BONE = = lamellar bone   Compact bone Cancellous bone = spongy bone
  24. 24. SECUNDARY BONE MATURE BONE Present in adults Characteristics smaller number of osteocytes bone matrix abundant, well calcified arranged in lamellae regular arrangement of collagen fibers lamellae form osteons (Haversian systems) great resistance to mechanical forces
  26. 26. Endosteum Thin layer of connective tissue with osteoprogenitor cells Lines internal surfaces of the bone
  27. 27. PRIMARY BONE IMMATURE BONE formed in embryo during bone formation develops in repair process after fracture replaced by mature bone irregular array of collagen fibrils in the organic part of matrix smaller calcification many osteocytes, little of bone matrix smaller mechanical resistance
  28. 28. HISTOGENESIS Intramembranous ossification on the ground of mesenchymal tissue formation of flat bones e.g. bones of the skull Endochondral ossification on the ground of cartilaginous model of the bone formation of long bones
  29. 29. INTRAMEMBRANOUS OSSIFICATION 1. penetration of blood vessels into mesenchymal tissue 2. mesenchymal cells differentiate into osteoblasts 3. formation of bone spicules
  30. 30. ENDOCHONDRAL OSSIFICATION 1. formation of bone collar within an inner layer of perichondrium of the diaphysis (intramembranous ossification)
  31. 31. ENDOCHONDRAL OSSIFICATION 2. hypertrophy of chondrocytes deposition of calcium salts in the cartilage matrix degeneration of chondrocytes
  32. 32. ENDOCHONDRAL OSSIFICATION 3. penetration of osteogenic bud across bone collar into degenerated cartilage
  33. 33. ENDOCHONDRAL OSSIFICATION 4. phagocytes resorb the cartilage osteoblasts start the production of bone matrix on the remnants of cartilage PRIMARY OSSIFICATION CENTER
  34. 34. BONE GROWTH FLAT BONES 1. Formation of bone on the external surface osteoprogenitor cells of periosteum (intramembranous ossification) 2. Resorption of bone on the internal surface osteoclasts
  35. 35. BONE GROWTH LONG BONES epiphyses - radial growth of cartilage cartilage is gradually replaced by bone the diaphysis increases in width by formation of bone by periosteum on the external surface diphyseal shaft grows in length as a result of the osteogenic activity of epiphyseal plate.
  36. 36. BONE AND CALCIUM REGULATORY FACTORS Parathormone (parathyroid) Bone Resorption Osteoclasts Osteocytes “osteocytic osteolysis” Bone Growth Somatotrophin (pituitary) Calcium Flux Calcitonin (parafollicular cells of thyroid) Nutritional Factors: Calcium & Vitamin D Deficiency Child- Ricketts Adult- osteomalacia Vitamin C Deficiency Scurvy- matrix not calicifiable