Skeletal System

1. Skeletal System Bones and Skeletal Tissue

2. Bones and Cartilages of the Human Body Figure 6.1

3. How are bones classified? • Axial skeleton – bones of the skull, vertebral column, and rib cage • Appendicular skeleton – bones of the upper and lower limbs, shoulder, and hip

5. Long bones • Long bones – longer than they are wide (e.g., humerus and femur) Figure 6.2a

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

7. Flat bones • Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones) Figure 6.2c

8. Irregular bones • Irregular bones – bones with complicated shapes (e.g., vertebrae and hip bones) Figure 6.2d

9. What are the functions 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 • Mineral storage – reservoir for minerals, especially calcium and phosphorus • Blood cell formation – hematopoiesis occurs within the marrow cavities of bones

10. What is the Gross Anatomy of Bones? • Compact bone – dense outer layer • Spongy bone – honeycomb of trabeculae (little beams) filled with red bone marrow

12. What is the structure of a 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

13. Structure of Long Bone • Epiphyses • Expanded ends of long bones • 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

14. Structure of Long Bone Figure 6.3a,b

15. What are the bone membranes? • Periosteum – double-layered protective membrane • Outer fibrous layer is dense regular CT • 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 • Sharpey’s fibers: secures the underlying bone to the periosteum. They are tufts of collagen fibers. • Endosteum – delicate membrane covering internal surfaces of bone

16. Structure of Long Bone Figure 6.3a, c

17. What is the structure of short, irregular, and flat bones? • Thin plates of periosteum-covered compact bone on the outside with endosteum-covered spongy bone on the inside • Have no diaphysis or epiphyses • Contain bone marrow between the trabeculae Figure 6.4

18. Where is the location of hematopoietic tissue (Red Marrow)? • In infants • Found in the medullary cavity and all areas of spongy bone • In adults • Found in the middle of flat bones, and the head of the femur and humerus

19. 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

20. Microscopic Structure of Bone: Compact Bone Figure 6.5a, b

21. What is the chemical composition of bone? (Organic) • Osteoblasts – bone-forming cells • Osteocytes – mature bone cells • Osteoclasts – large cells that reabsorb or break down bone matrix

22. 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

23. What are the types of markings found on bones? • Bulges, depressions, and holes that serve as: • Sites of attachment for muscles, ligaments, and tendons • Joint surfaces • Conduits for blood vessels and nerves

24. 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

25. 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

26. Bone Markings: 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

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

28. How do bones develop? • 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

29. 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

30. Functional Zones in Long Bone Growth • Growth zone – cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis • Transformation zone – older cells enlarge, the matrix becomes calcified, cartilage cells die, and the matrix begins to deteriorate • Osteogenic zone – new bone formation occurs

34. Long Bone Growth and Remodeling • Growth in length – cartilage continually grows and is replaced by bone as shown • Remodeling – bone is reabsorbed and added by appositional growth as shown Figure 6.10

35. Fracture Repair