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Chapter 6

Chapter 6. Bones and Cartilage Developmental Changes Ossification Homeostasis Repair. Cartilage. Hyaline – articular, tracheal rings, costal cartilages, nose apex Elastic – 2 locations: ear, epiglottis

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Chapter 6

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  1. Chapter6 • Bones and Cartilage • Developmental Changes • Ossification • Homeostasis • Repair

  2. Cartilage • Hyaline – articular, tracheal rings, costal cartilages, nose apex • Elastic – 2 locations: ear, epiglottis • Fibrocartilage – dense collagen interspersed w/ chondrocytes, & found in vertebral discs & menisci

  3. Cartilage cont. • Cartilage growth is limited by a lack of blood vessels and nerve supply. • Overall thickness limited by diffusion from the perichondral BV’s into the cartilage. • Consists of flexible matrix which accommodates mitosis making it an excellent embryonic skeleton

  4. 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

  5. Bone Shapes/Types 206 bones in the human body Axial or Appendicular Shape and size relates to the function • Long – limbs (NOT overall size, L vs. W) • Short – wrist & ankle, patella • sesamoid bones – alter the dirction of tendon force • Flat – sternum, scapula, ribs, & skull • Irregular – vertebrae and hips (pelvic bones)

  6. Classification of Bones: By Shape • Long bones – longer than they are wide (e.g., humerus) Figure 6.2a

  7. Classification of Bones: By Shape • Short bones • Cube-shaped bones of the wrist and ankle • Bones that form within tendons (e.g., patella) Figure 6.2b

  8. Classification of Bones: By Shape • Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones) Figure 6.2c

  9. Classification of Bones: By Shape • Irregular bones – bones with complicated shapes (e.g., vertebrae and hip bones) Figure 6.2d

  10. Bone Functions • Support • Protect • Movement • Mineral Reservoir – Ca++ and Phosphate • Blood Cells – hematopoiesis in marrow cavity

  11. Bone Markings • Projections, depressions, and openings serve as sites of tendon (muscle) or ligament attachment, as joint surfaces, or passageways for BV’s or nerves • See Table 6.1, page 179 for descriptions

  12. Bone Markings: Projections – Sites of Muscle and Ligament Attachment • Tuberosity – rounded projection • Crest – narrow, prominent ridge of bone • Trochanter – large, blunt, irregular surface • Line – narrow ridge of bone

  13. Bone Markings: Projections – Sites of Muscle and Ligament Attachment • Tubercle – small rounded projection • Epicondyle – raised area above a condyle • Spine – sharp, slender projection • Process – any bony prominence

  14. Bone Markings: Projections – 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

  15. 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

  16. Bone Markings Table 6.1

  17. Bone Texture • Compact – dense cortical bone, is the external bone structure • Spongy – a.k.a. cancellous bone is the honeycomb-like internal bone with trabechulae (spaces where marrow exists)

  18. Long Bone Structure • Diaphysis – shaft, generally compact bone with central marrow cavity (yellow marrow) • Epiphyses(is) – bone ends that are expanded. They have compact exterior and spongy interior, covered by articular cartilage • Epiphyseal plate (line) – a.k.a. metaphysis located between diaphysis and epiphysis • Membranes – periosteum w/ inner layer containing osteoblasts & osteoclasts. Has BV’s, nerves & lymphatics enter at nutrient foramen. Attached by Sharpey’s fibers. Endosteum covers trabechulae.

  19. 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

  20. 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

  21. 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 • Haversian, or central canal – central channel containing blood vessels and nerves • 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

  22. 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

  23. Microscopic Structure of Bone: Compact Bone Figure 6.6a, b

  24. Microscopic Structure of Bone: Compact Bone Figure 6.6a

  25. Microscopic Structure of Bone: Compact Bone Figure 6.6b

  26. Microscopic Structure of Bone: Compact Bone Figure 6.6c

  27. 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

  28. 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

  29. Bone Development • Osteogenesis and ossification – the process of bone tissue formation, which leads to: • The formation of the bony skeleton in embryos • Bone growth until early adulthood • Bone thickness, remodeling, and repair

  30. 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

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

  32. 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

  33. Stages of Intramembranous Ossification Figure 6.7.1

  34. Stages of Intramembranous Ossification Figure 6.7.2

  35. Stages of Intramembranous Ossification Figure 6.7.3

  36. Stages of Intramembranous Ossification Figure 6.7.4

  37. Bone Formation • Endocondral Ossification

  38. Endochondral Ossification • Begins in the second month of development • Uses hyaline cartilage “bones” as models for bone construction • Requires breakdown of hyaline cartilage prior to ossification

  39. Stages of Endochondral Ossification • Formation of bone collar • Cavitation of the hyaline cartilage • Invasion of internal cavities by the periosteal bud, and spongy bone formation • Formation of the medullary cavity; appearance of secondary ossification centers in the epiphyses • Ossification of the epiphyses, with hyaline cartilage remaining only in the epiphyseal plates

  40. Secondary ossificaton center Articular cartilage Spongy bone Epiphyseal blood vessel Deteriorating cartilage matrix Hyaline cartilage Epiphyseal plate cartilage Spongy bone formation Primary ossification center Medullary cavity Bone collar Blood vessel of periosteal bud 1 Formation of bone collar around hyaline cartilage model. 2 Cavitation of the hyaline carti- lage within the cartilage model. 3 Invasion of internal cavities by the periosteal bud and spongy bone formation. 4 Formation of the medullary cavity as ossification continues; appearance of sec- ondary ossification centers in the epiphy- ses in preparation for stage 5. 5 Ossification of the epiphyses; when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages. Stages of Endochondral Ossification Figure 6.8

  41. Hyaline cartilage Primary ossification center Bone collar 1 Formation of bone collar around hyaline cartilage model. Stages of Endochondral Ossification Figure 6.8

  42. Deteriorating cartilage matrix 1 Formation of bone collar around hyaline cartilage model. 2 Cavitation of the hyaline carti- lage within the cartilage model. Stages of Endochondral Ossification Figure 6.8

  43. Spongy bone formation Blood vessel of periosteal bud 1 Formation of bone collar around hyaline cartilage model. 2 Cavitation of the hyaline carti- lage within the cartilage model. 3 Invasion of internal cavities by the periosteal bud and spongy bone formation. Stages of Endochondral Ossification Figure 6.8

  44. Secondary ossificaton center Epiphyseal blood vessel Medullary cavity 1 Formation of bone collar around hyaline cartilage model. 2 Cavitation of the hyaline carti- lage within the cartilage model. 3 Invasion of internal cavities by the periosteal bud and spongy bone formation. 4 Formation of the medullary cavity as ossification continues; appearance of sec- ondary ossification centers in the epiphy- ses in preparation for stage 5. Stages of Endochondral Ossification Figure 6.8

  45. Articular cartilage Spongy bone Epiphyseal plate cartilage 1 Formation of bone collar around hyaline cartilage model. 2 Cavitation of the hyaline carti- lage within the cartilage model. 3 Invasion of internal cavities by the periosteal bud and spongy bone formation. 4 Formation of the medullary cavity as ossification continues; appearance of sec- ondary ossification centers in the epiphy- ses in preparation for stage 5. 5 Ossification of the epiphyses; when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages. Stages of Endochondral Ossification Figure 6.8

  46. Secondary ossificaton center Articular cartilage Spongy bone Epiphyseal blood vessel Deteriorating cartilage matrix Hyaline cartilage Epiphyseal plate cartilage Spongy bone formation Primary ossification center Medullary cavity Bone collar Blood vessel of periosteal bud 1 Formation of bone collar around hyaline cartilage model. 2 Cavitation of the hyaline carti- lage within the cartilage model. 3 Invasion of internal cavities by the periosteal bud and spongy bone formation. 4 Formation of the medullary cavity as ossification continues; appearance of sec- ondary ossification centers in the epiphy- ses in preparation for stage 5. 5 Ossification of the epiphyses; when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages. Stages of Endochondral Ossification Figure 6.8

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