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Chapter 4 Cartilage and Bone

Chapter 4 Cartilage and Bone. 1. Cartilage: organ=Cartilage tissue+perichondrium . 1) structure of cartilage tissue ---cell: chondrocyte ---cartilage matrix. ① chondrocyte: ---Structure: LM embedded in cartilage lacuna peripheral cells:

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Chapter 4 Cartilage and Bone

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  1. Chapter 4 Cartilage and Bone

  2. 1. Cartilage: organ=Cartilage tissue+perichondrium

  3. 1) structure of cartilage tissue ---cell: chondrocyte ---cartilage matrix

  4. ① chondrocyte: ---Structure: LM • embedded in cartilage lacuna • peripheral cells: --small and immature --single and flattened • central cell: --large and mature, --round and in group of 2-8 cells --small and round nucleus --basophilic cytoplasm --EM: rich in RER and Golgi complex

  5. *isogenous group: several cells locates in one lacuna, which are derived from a single(same) parent cell

  6. ② Cartilage matrix ---ground substance: • proteoglycan: --same to loose CT --there are more chondroitin sulfate distributed at the periphery of cartilage lacuna---called as cartilage capsule(basophilic) • chondronectin • water ---fiber: type and number of fiber depends on the type of cartilage

  7. 2) Classification: according to the fiber • Hyaline cartilage: • less collagenous fibril←type II collagen • articular surface, rib cartilage, trachea and bronchi

  8. Fibrous cartilage: • large amount of collagenous fiber bundles • cells are small and less • intervertebral disc, symphysis pubis

  9. Elastic cartilage: • large amount of elastic fiber • external ear, epiglottis

  10. 3) perichondrium two layers: ---out layer: contain more fiber-protection ---inner layer: more cells-osteoprogenitor cell(fusiform in shape)

  11. 4) growth of cartilage ---interstitial growth: • inner chondrocyte proliferation→ produce fiber and matrix. • immature cartilage ---appositional growth: • osteoprogenitor cell→cartilage cell (chondrocyte) → produce fiber and matrix. • growing and mature cartilage

  12. 2.Bone ---consists of bone tissue, periosteum and endosteum, bone marrow

  13. 1)Bone tissue ① Cells:

  14. a. osteoprogenitor cell: stem cell ---structure: • fusiform, small • ovoid nucleus • slight basophilic cytoplasm • exist in periosteum and endosteum ---function: differentiated into osteoblast and chondrocyte

  15. b. osteoblast: ---structure: LM: • single layer of cuboidal or low columnar cell • round nucleus • basophilic cytoplasm • located on the surface of bone tissue

  16. EM: • fine processes • rich in RER, Golgi complex

  17. ---function: ⅰ.synthesize bone collagen fiber and ground substance-osteoid ⅱ.release matrix vesicle: • 0.1um in diameter • membrane-coated • ALPase(Alkaline phosphatase), ATPase and pyrophosphatase and phosphoester (phospholipid) • calcium, crystal of bone salt and calbindin • function: promote calcification

  18. c.osteocyte ---structure: • flattened cell with multiple long thin processes • located in bone lacuna and bone canaliculus • basophilic cytoplasm • adjacent cells connect in bone canaliculus by gap junctions ---function: • Maintain bone matrix • regulate the balance of calcium and phosphonium

  19. d. osteoclast ---structure: LM: • multinuclear large cell, 30-100um • 6-50 nuclei • acidophilic cytoplasm • located at peripheral part of bone

  20. EM: • ruffled border-processes • light zone: --under the ruffled border --microfilament • primary lysosome, pinosome and secondary lysosome • RER, mito. and Golgi ---function: dissolve and absorb bone matrix

  21. ②Bone matrix ---organic matter: • bone collagen fiber -collagenous fiber (type I collagen) • ground substance: glycosaminoglycan

  22. glycoproteins: • osteocalcin: involve in calcification of bone and regulate absorption of bone • osteonectin: related to adherence between cell and bone matrix, regulate calcification of bone • osteopontin

  23. ---inorganic matter: bone salts Hydroxyapatite crystal: • Ca10(PO4)6(OH)2 • pin-shaped • 10-20 nm • longitudinal arranged *bone lamella: bone matrix arranged in layers at different direction

  24. 2) Architacture of long bone Long bone is an organ, made up of bone tissue(shaft and epiphyses), periosteum and endosteum, bone marrow

  25. ① shaft: consists of compact bone a.circumferential lamella: /outer concentrically-arranged /inner around inner surface of bone

  26. b.Haversian system (osteon): /cylindric structure, 3-5mm /central canal: N, BV, CT /Haversian lamella: 4-20 layers

  27. c.interstitial lamella: /irregular lamella /remnant of Haversian or circumferential lamella *perforating canal: /transverse canal /connect with Haversian canal

  28. ② epiphyses: composed of spongy bone ---trabeculae: • formed by parallelly-arranged lamella • form a spongy-liked network ---Bone marrow: hemopoietic tissue

  29. ③ periosteum and endosteum: CT membrane ---periosteum: DCT • outer layer:more fiber bundles form perforating fiber • inner layer: rich in BV, N and osteoprogenitor cells ---endosteum: thin, a layer of osteoprogenitor cell and CT ---function: provide nutrition and osteoblast for bone growth and repairing

  30. 3)osteogenesis

  31. ①basal processes ---formation: osteoprogenitor cell→ osteoblast → osteoid ↓ ↓calcification osteocyte + bone matrix bone tissue ---absorption: osteoclast →dissolve bone tissue→reconstruction

  32. ②basal manner a. intramembranous ossification: ---CT membrane →osteoprogenitor cell → osteoblast→ossification center→bone trabeculae →thicker and longer ---flattened bone and irregular bone formed in these manner

  33. b. endochondral ossification: e.g. long bone ⅰ.formation of cartilage model • Mesenchymal cell→osteoprogenitor cell →chondroblast→chondrocyte→cartilage model( consists of hyaline cartilage and perichondrium) ⅱ.formation of bone collar • osteoprogenitor cell (perichondrium) → osteoblast →bone tissue * These bone tissue surround the central segment of cartilage model as collar-shaped, so called bone collar

  34. ⅲ.formation of primary ossification center and bone marrow cavity • chondrocytes of model center stop differentiation, enlarge in size, calcification, dead →CT, BV in periosteum enter degenerating zone→osteoblast, osteoclast, osteoprogenitor cell and mesenchymal cell enter at same time→ossification→primary ossification center

  35. primary bone marrow cavity(space between trabeculae) →bone marrow cavity

  36. ⅳ.Formation of secondary ossification center and epiphyses • secondary ossification center appears at the two end of long bone(epiphyses) • epiphyseal plate: cartilage layer between epiphysis and bone shaft, growing zone

  37. ③Further growth of bone ---Become longer: • by growth of epiphyseal plate • from epiphyses to shaft, four zones can be seen: i.reserve cartilage zone: cell is small, round and basophilic ii.proliferating cartilage zone: cell is flattened, isogenous group cell arrange in single line

  38. iii. calcified cartilage zone: cell become large, mature, round and degenerated, strong basophilic iv.ossification zone: ---become thicker: periosteum cell → osteoprogenitor cell→osteoblast

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