1. PowerPoint ® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham HUMAN ANATOMY fifth edition MARIEB | MALLATT | WILHELM 6 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Bones and Skeletal Tissues PART 2

2. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Composition of Bone  35% organic components  Composed of cells, fibers, and organic substances  Collagen – abundant  65% inorganic mineral salts  Primarily calcium phosphate  Resists compression

3. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Bone Development  Ossification (osteogenesis) – bone-tissue formation  Membrane bones – formed directly from mesenchyme  Intramembranous ossification  Other bones – develop initially from hyaline cartilage  Endochondral ossification

4. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Intramembranous Ossification Figure 6.9, steps 1–2

5. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Intramembranous Ossification Figure 6.9, steps 3–4

6. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Endochondral Ossification  All bones except some bones of the skull and clavicles  Bones are modeled in hyaline cartilage  Begins forming late in the second month of embryonic development  Continues forming until early adulthood

7. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Stages in Endochondral Ossification Figure 6.10

8. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of Epiphyseal Growth Areas  In epiphyseal plates of growing bones  Cartilage is organized for quick, efficient growth  Cartilage cells form tall stacks  Chondroblasts at the top of stacks divide quickly  Pushes the epiphysis away from the diaphysis  Lengthens entire long bone

9. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of Epiphyseal Growth Areas  Older chondrocytes signal surrounding matrix to calcify  Older chondrocytes then die and disintegrate  Leaves long trabeculae (spicules) of calcified cartilage on diaphysis side  Trabeculae are partly eroded by osteoclasts  Osteoblasts then cover trabeculae with bone tissue  Trabeculae finally eaten away from their tips by osteoclasts

10. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Organization of Cartilage within Epiphyseal Plate of Growing Long Bone Figure 6.11

11. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Postnatal Growth of Endochondral Bones  During childhood and adolescence  Bones lengthen entirely by growth of the epiphyseal plates  Cartilage is replaced with bone CT as quickly as it grows  Epiphyseal plate maintains constant thickness  Whole bone lengthens

12. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Regulation of Bone Growth  Growth hormone – produced by the pituitary gland  Stimulates epiphyseal plates  Thyroid hormone – ensures that the skeleton retains proper proportions  Sex hormones (estrogen and testosterone)  Promote bone growth  Later induces closure of epiphyseal plates

13. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Postnatal Growth of Endochondral Bones  As adolescence draws to an end  Chondroblasts divide less often  Epiphyseal plates become thinner  Cartilage stops growing  Replaced by bone tissue  Long bones stop lengthening when diaphysis and epiphysis fuse

14. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Bone Remodeling  Bone is dynamic living tissue  500 mg of calcium may enter or leave the adult skeleton each day  Cancellous bone of the skeleton is replaced every 3 – 4 years  Compact bone is replaced every 10 years

15. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Postnatal Growth of Endochondral Bones  Growing bones widen as they lengthen  Osteoblasts – add bone tissue to the external surface of the diaphysis  Osteoclasts – remove bone from the internal surface of the diaphysis  Appositional growth – growth of a bone by addition of bone tissue to its surface

16. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Bone Remodeling  Bone deposit and removal  Occurs at periosteal and endosteal surfaces  Bone remodeling  Bone deposition – accomplished by osteoblasts  Bone reabsorption – accomplished by osteoclasts

17. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Remodeling, Spongy Bone Figure 6.12

18. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Osteoclast – A Bone-Degrading Cell  A giant cell with many nuclei  Crawls along bone surfaces  Breaks down bone tissue  Secretes concentrated HCl  Lysosomal enzymes are released Figure 6.13a

19. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Repair of Bone Fractures  Simple and compound fractures  Treatment by reduction  Closed reduction  Open reduction

20. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Stages of Healing a Fracture Figure 6.14

21. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Common Types of Fractures Table 6.2 (1 of 3)

22. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Common Types of Fractures Table 6.2 (2 of 3)

23. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Common Types of Fractures Table 6.2 (3 of 3)

24. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of Bones  Osteoporosis  Characterized by low bone mass  Bone reabsorption outpaces bone deposition  Occurs most often in women after menopause

25. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Osteoporosis Figure 6.15

26. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of Bones  Osteomalacia  Occurs in adults – bones are inadequately mineralized  Rickets  Occurs in children – analogous to osteomalacia

27. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of Bones  Paget’s disease  Characterized by excessive rate of bone deposition  Osteosarcoma  A form of bone cancer

28. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Skeleton Throughout Life  Cartilage grows quickly in youth  Skeleton shows fewer chondrocytes in the elderly  Bones are a timetable  Mesoderm  Gives rise to embryonic mesenchyme cells  Mesenchyme  Produces membranes and cartilage  Membranes and cartilage ossify

29. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Skeleton Throughout Life  Skeleton grows until the age of 18–21 years  In children and adolescents  Bone formation exceeds rate of bone reabsorption  In young adults  Bone formation and bone reabsorption are in balance  In old age reabsorption predominates  Bone mass declines with age