The Skeletal System

1. The Skeletal System • All parts are connective tissue: • Bones (skeleton) • Cartilages • Ligaments • two divisions: • Axial skeleton • Appendicular skeleton

2. Functions of Skeleton and Bones • Support of the body • Protection of soft organs • Movement due to attached skeletal muscles • Storage of minerals and fats • Blood cell formation

3. Bones of the Human Body • 206 bones • Two basic types • Compact bone • Dense • Calcium crystals • Spongy bone • Trabeculae - “little beams” • Many open spaces Figure 5.2b

4. Gross Anatomy of a Long Bone Epiphysis • Ends of the bone - spongy bone • Red bone marrow Diaphysis • Shaft - compact bone • Medullary cavity Periosteum Figure 5.2a

5. Structure of Bone Osteon - cylinder of bone, has central canal with blood vessels Osteocytes within spaces (lacunae), connected by small canals (canaliculi) Figure 5.1

6. Cartilage and Ligaments • Ligaments - dense fibrous connective tissue • Collagen fibers, fibroblasts • Cartilage - collagen and elastin fibers in base of water. Smooth and flexible substance • used to reduce friction, provide support under pressure at joints

7. Changes in the Human Skeleton • Embryos - hyaline cartilage • Cartilage replaced by bone = ossification • done by osteoblasts - bone building cells • Secrete osteoid (proteins, fibers, enzymes) • Osteoid replaced by calcium phosphate salts • Cartilage remains in nose, ribs, joints, and epiphyseal plates, ends of bones

8. Bone Development (cont.) Figure 5.2

9. Types of Bone Cells • Chondrocytes • Cartilage-forming cells • Osteocytes • Mature bone cells • Osteoblasts • Bone-forming cells • Osteoclasts • Bone-destroying cells • Break down bone matrix for remodeling and release of calcium

10. Mature Bone Remodeling and Repair • Changes in shape, size, strength • Dependent on diet, exercise, age • Bone cells regulated by hormones • Parathyroid hormone (PTH): removes calcium from bone • Calcitonin: adds calcium to bone

11. Stages in the Healing of a Bone Fracture Fibrocartilage callus is replaced by a bony callus • Bony callus is remodeled to form a permanent patch • Hematoma (blood-filled swelling) is formed • Break is splinted by fibrocartilage to form a callus Figure 5.5

12. The Axial Skeleton • Forms the longitudinal part of the body • Divided into 3 parts • Skull • Vertebral column • Bony thorax

13. The Skull • Two sets of bones • Cranium • Facial bones • Bones are joined by sutures • Only the mandible is attached by a freely movable joint

14. The Hyoid Bone • only bone that does not articulate with another bone • Serves as moveable base for the tongue Figure 5.12

15. Paranasal Sinuses • Functions of paranasal sinuses • Lighten the skull • Give resonance and amplification to voice Figure 5.10

16. The Fetal Skull • Fontanelles – fibrous membranes connecting the cranial bones • Allow the brain to grow • Convert to bone within 24 months after birth Figure 5.13

17. The Vertebral Column • 5 regions, 33 bones • Spine has a normal curvature • Vertebrae separated by intervertebral discs Figure 5.7

18. The Bony Thorax • Made-up of two parts • Sternum • Ribs (12 pr) • Forms a cage to protect major organs Figure 5.19a

19. The Appendicular Skeleton • Limbs (appendages) • Pectoral girdle • Pelvic girdle

20. Bones of the Pectoral Girdle • Clavicle – collarbone • Scapula – shoulder blade Figure 5.20a–b

21. Bones of the Upper Limb • The arm - Humerus • The forearm - Ulna and Radius Hand - Carpals Metacarpals Phalanges Figure 5.21a–b

22. The Pelvis Figure 5.23a

23. Gender Differences of the Pelvis Figure 5.23c

24. Bones of the Lower Limbs Femur – thigh bone Tibia - bears weight Fibula - helps rotation with ankle Tarsals - ankle Metatarsals - foot Phalanges - toes Figure 5.24a–b

25. Joints (Articulations) • Classified by degree of movement • Fibrous joint: immovable; e.g., fontanels • Cartilagenous joint: slightly movable, cartilage connection; e.g., backbone • Synovial joint: freely movable

26. Synovial Joints - movable; all limbs • Joint capsule: synovial membrane + hyaline cartilage • Synovial membrane secretes synovial fluid as lubricant • Hyaline cartilage cushions

27. Disorders, Inflammatory Conditions Associated with Joints • Sprains: stretched or torn ligaments • Bursitis and tendinitis: inflammations

28. Clinical Forms of Arthritis • Osteoarthritis • Cartilage wears out, pain, inflammation • normal aging processes • Rheumatoid arthritis • autoimmune disease –attacks the joints • inflammation of synovial membranes • Cartilage lost, bones fused, leads to deformities