Bone & Skeletal Tissue

1. Bone & Skeletal Tissue Chapter 6

2. Functions of the Skeletal system • Support • Protection • Movement • Mineral storage • Hematopoiesis (blood cell formation)

3. Skeletal Cartilages

4. Cartilages of the respiratory tract

5. Classification of Bones • Bone are identified by: • shape • internal tissues • bone markings

6. Bone Shapes • Long bones • Flat bones • Sutural bones • Irregular bones • Short bones • Sesamoid bones

7. Long Bones Figure 6–1a

8. Long Bones • Are long and thin • Are found in arms, legs, hands, feet, fingers, and toes

9. Flat Bones Figure 6–1b

10. Flat Bones • Are thin with parallel surfaces • Are found in the skull, sternum, ribs, and scapula

11. Sutural Bones Figure 6–1c

12. Sutural Bones • Are small, irregular bones • Are found between the flat bones of the skull

13. Irregular Bones Figure 6–1d

14. Irregular Bones • Have complex shapes • Examples: • spinal vertebrae • pelvic bones

15. Short Bones Figure 6–1e

16. Short Bones • Are small and thick • Examples: • ankle • wrist bones

17. Sesamoid Bones Figure 6–1f

18. Sesamoid Bones • Are small and flat • Develop inside tendons near joints of knees, hands, and feet

19. Bone Markings • Depressions or grooves: • along bone surface • Projections: • where tendons and ligaments attach • at articulations with other bones • Tunnels: • where blood and nerves enter bone

20. Bone Markings

21. Bone Markings Table 6–1 (2 of 2)

22. Long Bones • The femur Figure 6–2a

23. Structure of a long bone The Humerus

24. Long Bones • Diaphysis: • the shaft • Epiphysis: • wide part at each end • articulation with other bones • Metaphysis: • where diaphysis and epiphysis meet

25. Flat Bones • The parietal bone of the skull Figure 6–2b

26. Compact Bone Structure

27. Spongy Bone Figure 6–6

28. Spongy Bone Structure

29. Bone Cells • Make up only 2% of bone mass: • osteocytes • osteoblasts • osteoprogenitor cells • osteoclasts

30. Bone Cells: Osteoblasts, Osteocytes & Osteoclasts

31. Periosteum Figure 6–8a

32. Endosteum Figure 6–8b

33. Bone Development • Human bones grow until about age 25 • Osteogenesis: • bone formation • Ossification: • the process of replacing other tissues with bone

34. Intramembranous Ossification • Also called dermal ossification: • because it occurs in the dermis • produces dermal bones such as mandible and clavicle • There are 3 main steps in intramembranous ossification

35. Intramembranous Ossification: Step 1 Figure 6–11 (Step 1)

36. Intramembranous Ossification: Step 1 • Mesenchymal cells aggregate: • differentiate into osteoblasts • begin ossification at the ossification center • develop projections called spicules

37. Step 2

38. Intramembranous Ossification: Step 2 • Blood vessels grow into the area: • to supply the osteoblasts • Spicules connect: • trapping blood vessels inside bone

39. Step 3 Figure 6–11 (Step 3)

40. Intramembranous Ossification: Step 3 • Spongy bone develops and is remodeled into: • osteons of compact bone • periosteum • or marrow cavities

41. Endochondral Ossification • Ossifies bones that originate as hyaline cartilage • Most bones originate as hyaline cartilage

42. Endochondral Ossification: Step 1 • Chondrocytes in the center of hyaline cartilage: • enlarge • form struts and calcify • die, leaving cavities in cartilage Figure 6–9 (Step 1)

43. Step 2

44. Endochondral Ossification: Step 2 • Blood vessels grow around the edges of the cartilage • Cells in the perichondrium change to osteoblasts: • producing a layer of superficial bone around the shaft which will continue to grow and become compact bone (appositional growth)

45. Step 3 • Blood vessels enter the cartilage: • bringing fibroblasts that become osteoblasts • spongy bone develops at the primary ossification center

46. Step 4 • Remodeling creates a marrow cavity: • bone replaces cartilage at the metaphyses

47. Step 5 • Capillaries and osteoblasts enter the epiphyses: • creating secondary ossification centers

48. Step 6

49. Endochondral Ossification: Step 6 • Epiphyses fill with spongy bone: • cartilage within the joint cavity is articulation cartilage • cartilage at the metaphysis is epiphyseal cartilage

50. Endochondral Ossification • Appositional growth: • compact bone thickens and strengthens long bone with layers of circumferential lamellae PLAY Endochondral Ossification Figure 6–9 (Step 2)