1. Bones and Muscles

2. How the Skeletal System Works There are 206 bones in the body The smallest bones in the body are in the inner ear The largest bone in the body is the femur Ligaments attach bone to bone; tendons attach bone to muscle

3. Functions of the Skeletal System Provides support to the body Protects internal tissues and organs from damage Acts as a framework for attached muscle Allows movement of limbs and digits Produces new red and white blood cells Stores fat and minerals, such as calcium and phosphorus

4. Bones Bones are living tissues The outer layer is hard, densely packed and compact The inner layer is spongy bone, a less dense bone with network of cavities filled with red bone marrow, where blood cells are produced Some bones contain yellow bone marrow, a type of connective tissue that stores fat

5. Categories Bones are categorized by shape: Long: humerus Short: carpals and tarsals Flat: ribs Irregular: vertebrae

6. Connective Tissue Three types of connective tissue: Cartilage: strong, flexible connective tissue that can act as a cushion between two bones to reduce friction; also acts as the flexible structure for soft parts of the body such as the tip of the nose or outer ear Ligaments: a band of fibrous, slightly elastic connective tissue that attaches one bone to another Tendons: a fibrous cord that attaches muscle to the bone Ossification: the process by which bone is formed, renewed, and repaired

7. Joints Points at which bones meet Some joints, such as the ones between bones of the skull, do not move Flexible joints include ball-and-socket joints, hinge joints, pivot joints, and ellipsoidal joints

8. Caring for the Skeletal System Eat a healthy diet Get regular physical activity Have regular checkups Eat foods high in calcium, vitamin D and phosphorus to prevent skeletal disorders Weight bearing exercise such as walking or weight training helps bones stay strong

9. Understanding Skeletal Problems Fractures: any type of break in a bone Compound: a fracture that sticks out through the skin Simple: the broken bone does not break the skin Hairline: if parts of the bone do not separate Transverse: when the fracture is completely across the bone Comminuted: when the bone shatters into more than two pieces

10. Injuries to Joints Dislocation: when a bone slips out of place, tearing ligaments that attach the bone at the joint Torn cartilage: can result from a sharp blow to a joint or severe twisting of a joint. Bursitis: results fro the painful inflammation of bursa, a fluid-filled sac that helps reduce friction in joints Bunions: painful swellings of the bursae in the first joints of the big toes Arthritis: the inflammation of a joint, resulting from injury, natural wear and tear, or autoimmune disease

11. Repetitive Motion Injury Prolonged, repeated movements such as sewing or computer work (carpal tunnel syndrome) can damage tissues Sports injuries: Tennis elbow The wearing of connective tissue that a baseball pitcher suffers due to the repetitive nature of pitching motions Shin splints Tiger Woods’ knee problems due to the repetitively violent nature of his golf swing

12. Osteoporosis A condition in which there is a progressive loss of bone tissue Bones weaken and become brittle Affects millions of older Americans Regular weight bearing physical activity stimulates bone cells to increase bone mass