Bones and Skeletal Tissues

1. Bones and Skeletal Tissues P A R T A

2. Skeletal Cartilage • Contains no blood vessels or nerves • Surrounded by the perichondrium (dense irregular connective tissue) that resists outward expansion • Three types – hyaline, elastic, and fibrocartilage

3. Hyaline Cartilage • Provides support, flexibility, and resilience • Is the most abundant skeletal cartilage • Is present in these cartilages: • Articular – covers the ends of long bones • Costal – connects the ribs to the sternum • Respiratory – makes up larynx, reinforces air passages • Nasal – supports the nose

4. Elastic Cartilage • Similar to hyaline cartilage, but contains elastic fibers • Found in the external ear and the epiglottis

5. Fibrocartilage • Highly compressed with great tensile strength • Contains collagen fibers • Found in menisci of the knee and in intervertebral discs

6. Growth of Cartilage • Appositional – cells in the perichondrium secrete matrix against the external face of existing cartilage • Interstitial – lacunae-bound chondrocytes inside the cartilage divide and secrete new matrix, expanding the cartilage from within • Calcification of cartilage occurs • During normal bone growth • During old age

7. Bones and Cartilages of the Human Body

8. Classification of Bones • Axial skeleton – bones of the skull, vertebral column, and rib cage • Appendicular skeleton – bones of the upper and lower limbs, shoulder, and hip

9. Classification of Bones: By Shape • Long bones – longer than they are wide (e.g., humerus)

10. Classification of Bones: By Shape • Short bones • Cube-shaped bones of the wrist and ankle

11. Classification of Bones: By Shape • Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones)

12. Classification of Bones: By Shape • Irregular bones – bones with complicated shapes (e.g., vertebrae and hip bones)

13. Classification of bones by shape • Sesamoid bones • Short bones located in a tendon • Patella

14. Function of Bones • Support – form the framework that supports the body and cradles soft organs • Protection – provide a protective case for the brain, spinal cord, and vital organs • Movement – provide levers for muscles

15. Function of Bones • Mineral storage – reservoir for minerals, especially calcium and phosphorus • Blood cell formation – hematopoiesis occurs within the marrow cavities of bones

16. Bone Markings • Bulges, depressions, and holes that serve as: • Sites of attachment for muscles, ligaments, and tendons • Joint surfaces • Conduits for blood vessels and nerves

17. Projections – Sites of Muscle and Ligament Attachment • Tubercle – small rounded projection • Tuberosity – rounded projection • Trochanter – large, blunt, irregular surface • Crest – narrow, prominent ridge of bone • Line – narrow ridge of bone

18. Projections – Sites of Muscle and Ligament Attachment • Epicondyle – raised area above a condyle • Spine – sharp, slender projection • Process – any bony prominence

19. Projections That Help to Form Joints • Head – bony expansion carried on a narrow neck • Facet – smooth, nearly flat articular surface • Condyle – rounded articular projection • Ramus – armlike bar of bone

20. Bone Markings: Depressions and Openings • Meatus – canal-like passageway • Sinus – cavity within a bone • Fossa – shallow, basin-like depression • Groove – furrow • Fissure – narrow, slit-like opening • Foramen – round or oval opening through a bone

21. Gross Anatomy of Bones: Bone Textures • Compact bone – dense outer layer • Spongy bone – honeycomb of trabeculae filled with yellow bone marrow

22. Structure of Long Bone • Diaphysis • Tubular shaft that forms the axis of long bones • Composed of compact bone that surrounds the medullary cavity • Yellow bone marrow (fat) is contained in the medullary cavity

23. Structure of Long Bone • Epiphyses • Expanded ends of long bones: distal and proximal • Exterior is compact bone, and the interior is spongy bone • Joint surface is covered with articular (hyaline) cartilage • Epiphyseal line separates the diaphysis from the epiphyses (metaphisis)

24. Structure of Long Bone

25. Structure of Long Bone

26. Structure of Long Bone

27. Structure of Long Bone

28. Bone Membranes • Periosteum – double-layered protective membrane • Outer fibrous layer is dense regular connective tissue • Inner osteogenic layer is composed of osteoblasts and osteoclasts • Richly supplied with nerve fibers, blood, and lymphatic vessels, which enter the bone via nutrient foramina

29. Bone Membranes • Secured to underlying bone by Sharpey’s fibers • Endosteum – delicate membrane covering internal surfaces of bone • It contains osteoclasts and osteoblasts

30. Structure of Short, Irregular, and Flat Bones • Thin plates of periosteum-covered compact bone on the outside with endosteum-covered spongy bone (diploë) on the inside • Have no diaphysis or epiphyses • Contain bone marrow between the trabeculae

31. Structure of a Flat Bone

32. Location of Hematopoietic Tissue (Red Marrow) • In infants • Found in the medullary cavity and all areas of spongy bone • In adults • Found in the diploë of flat bones, and the head of the femur and humerus

33. Microscopic Structure of Bone: Compact Bone • Haversian system, or osteon – the structural unit of compact bone • Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen. Concentric, circumferential, interstitial • Haversian, or central canal – central channel containing blood vessels and nerves

34. Microscopic Structure of Bone: Compact Bone • Volkmann’s canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal

35. Microscopic Structure of Bone: Compact Bone • Osteocytes – mature bone cells • Lacunae – small cavities in bone that contain osteocytes • Canaliculi – hairlike canals that connect lacunae to each other and the central canal

36. Microscopic Structure of Bone: Compact Bone

37. Microscopic Structure of Bone: Compact Bone

38. Microscopic Structure of Bone: Compact Bone

39. Microscopic Structure of Bone: Compact Bone

40. Chemical Composition of Bone: Organic • Osteoblasts – bone-forming cells • Osteocytes – mature bone cells • Osteoclasts – large cells that resorb or break down bone matrix • Osteoid – unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

41. Chemical Composition of Bone: Inorganic • Hydroxyapatites, or mineral salts • Sixty-five percent of bone by mass • Mainly calcium phosphates • Responsible for bone hardness and its resistance to compression

42. Bone Development • Osteogenesis (ossification) – the process of bone tissue formation • The formation of the bony skeleton in embryos • Bone growth until early adulthood • Bone thickness, remodeling, and repair • Calcification

43. Formation of the Bony Skeleton • Begins at week 8 of embryo development • Intramembranous ossification – bone develops from a fibrous membrane • Endochondral ossification – bone forms by replacing hyaline cartilage

44. Intramembranous Ossification • Formation of most of the flat bones of the skull and the clavicles • Fibrous connective tissue membranes are formed by mesenchymal cells

45. Stages of Intramembranous Ossification • An ossification center appears in the fibrous connective tissue membrane • Bone matrix is secreted within the fibrous membrane • Woven bone and periosteum form • Bone collar of compact bone forms, and red marrow appears

46. Stages of Intramembranous Ossification Figure 6.7.1

47. Stages of Intramembranous Ossification Figure 6.7.2

48. Stages of Intramembranous Ossification Figure 6.7.3

49. Stages of Intramembranous Ossification Figure 6.7.4

50. Bones and Skeletal Tissues P A R T B