Functions of Bones

1. Functions of Bones • 1. Gives the body its shape • 2. Support of the body’s weight • 3. Protection of soft organs • 4. Movement due to attached skeletal muscles. Joints act as levers. • 5. Storage of minerals and fats. Mainly Calcium and Phosphate. • 6. Blood cell formation. Red and White blood cells and Platelets are formed in the Red Marrow of Spongy Bone.

2. Gross Anatomy of a Long Bone • A bone is and organ. It is composed of bone, cartilage, fibrous connective, blood and nervous tissue. • Diaphysis • Shaft • Composed of compact bone • Epiphysis • Ends of the bone. Covered with Hyaline Cartilage where it articulates with another bone. • Composed mostly of spongy bone

4. Structures of a Long Bone • Periosteum • Outside covering of the diaphysis • Fibrous connective tissue membrane • Sharpey’s fibers • Secure periosteum to underlying bone • Arteries • Supply bone cells with nutrients

5. Medullary cavity Cavity of the shaft • Lined with epithelial cells called the Endosteum • Contains yellow marrow (mostly fat) in adults • Contains red marrow (for blood cell formation) in infants • Articular cartilage • Covers the external surface of the epiphyses • Made of hyaline cartilage • Decreases friction at joint surfaces

7. Types of Bone Cells • Osteocytes • Mature bone cells • Osteoblasts • Bone-forming cells. • Stores Calcium in bones when level in blood is high • Osteoclasts • Bone-destroying cells • Break down bone matrix for remodeling and release of calcium when level in blood is low. • Bone remodeling is a process by both osteoblasts and osteoclasts

8. Human Bone Development • In embryos, the skeleton is primarily Hyaline Cartilage (endochondral bones) and Fibrous Connective tissues (Intramembranous bones) • During development, much of this cartilage and fibrous connective tissue is replaced by bone • Cartilage remains in isolated areas • Bridge of the nose • Parts of ribs • Joints

9. Bone Growth • Epiphyseal plates allow for growth of long bone during childhood • New cartilage is continuously formed • Older cartilage becomes ossified • Cartilage is broken down • Bone replaces cartilage

10. Long Bone Formation and Growth

12. Functional Classification of Joints • Synarthroses – Immovable joints • Amphiarthroses – Slightly movable joints • Diarthroses – Freely movable joints

13. Immovable Joints • Bones united by fibrous connective tissue • Examples • Sutures of the Skull

14. Slightly Movable Joints • Bones connected by cartilage. Movement limited • Examples • Pubic symphysis • Intervertebral disks • Sacroiliac joint Figure 5.27d–e

15. Freely Movable Joints • Articular cartilage (hyaline cartilage) covers the ends of bones • Joint surfaces are enclosed by a fibrous articular capsule • Have a joint cavity filled with synovial fluid • Ligaments reinforce the joint

16. The Synovial (freely movable) Joint

17. Types of Synovial Joints Based on Shape

18. Types of Synovial Joints Based on Shape

19. Freely Movable Joints 1. Ball and Socket. • Movement in all planes and rotation. • Examples: Hip, Shoulder • Condyloid. Movement in all planes except rotation Examples: Metacarpal – Phalange, Occipital - Atlas • Plane Sliding or twisting movements Examples: Carpal-carpal, tarsal-tarsal

20. 4. Hinge • Movement up and down in one plane • Examples: Elbow, Knee, Phalange-Phalange • Pivot Movement of rotation only Examples: Proximal ends of the Ulna- Radius, Atlas Axis • Saddle Opposition movement Example: Trapezium-Metacarpal of the thumb

21. Types of Ordinary Body Movements • Flexion – Decreases the angle between bones • Extension – Increases the angle between bones • Hyperextension – Extension beyond 180o • Rotation – Movement of a bone around an axis • Abduction – Moving a limb away from the midline • Adduction – Movement of a limb toward the midline • Circumduction – Movement of a limb in a cone shaped pattern

22. Body Movements Figure 6.13a–c

24. Special Movements • Dorsiflexion – Pointing the toes upward • Plantar flexion – Pointing the toes downward • Inversion – Turning the sole medially • Eversion – Turning the sole laterally • Supination – Rotation of the palm upward • Pronation – Rotation of the palm downward • Opposition – Touching the fingertips with the thumb