Chapter 4 Cartilage and Bone

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: isogenous group --small and round nucleus --basophilic cytoplasm --EM: rich in RER and Golgi complex

5. Chondroblast secret matrix and fiber chondrocyte

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

7. 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) • water ---fiber: type and number of fiber depends on the type of cartilage

8. 2)Classification: according to the fiber Hyaline cartilage: less collagenous fibril articular surface, rib cartilage, trachea and bronchi

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

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

11. Fibrous cartilage Hyaline cartilage Elastic cartilage

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

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

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

15. Osteoprogenitor cell ↓ osteoblast ↓ osteocyte osteoclast • 1)Bone tissue ① Cells:

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

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

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

20. ---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焦磷酸酶 and phosphoester磷酸酯 (phospholipid) • calcium, crystal of bone salt • function: promote calcification

21. 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

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

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

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

28. *bone lamella: bone matrix arranged in layers at different direction

29. 2) Architacture of long bone Long bone is an organ, made up of bone tissue , periosteum and endosteum, bone marrow

30. ① shaft: consists of compact bone a.circumferential lamella: /outer circumferential lamella /inner circumferential lamella

31. b.Haversian system (osteon): /central canal: N, BV, CT /Haversian lamella: 4-20 layers

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

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

35. 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

36. 3)     osteogenesis

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

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

39. 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

40. 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

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

42. 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

43. reserve cartilage zone proliferating cartilage zone ③    Further 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

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

45. Thanks!