The skeletal System

1. The skeletal System

2. Functions of your skeletal system • The bones in your body are very much alive • Bones: main organs of the skeletal system; made of a form of connective tissue made up of bone cells surrounded by calcium and other minerals • There are five major functions of the skeletal system: • Gives shape and support • Protects internal organs • Major muscles are attached to bones and help them move • Blood cells are formed in the center of many bones • Major amounts of calcium and phosphorous compounds are stored in the skeleton for later use • Calcium and phosphorous make bones hard

3. Bone Structure • The surface of a living bone is covered with a tough, tight-fitting membrane • Under the membrane is a hard, strong layer called compact bone • Gives bone strength • Spongy bone is found in the ends of long bones • Has many small, open spaces that makes bones lightweight • The centers of long bones are filled with marrow • Some marrow is yellow and made up of fat cells • Red marrow makes two to three million red blood cells per second

4. Cartilage • The ends of bones are covered with a smooth, slippery, thick layer of tissue called cartilage • Does not contain blood vessels or minerals • Protects joints by acting as a shock absorber • Make movement easier because it lessens friction

5. Bone formation • Before you were born, your skeleton was made of cartilage • Over time, the cartilage was replaced by bone • At birth, your skeleton was made up of more than 300 bones • As you developed, some bones grew together so that you now have only 206 bones

6. Joints • Joint: any place where two or more of your bones come together • Bones are held in place at these joints by a tough band of tissue called a ligament • Immovable joint: allows little or no movement • Ex: the joints in the bones of your skull • Movable joint: required by all movement

7. Movable Joints • Pivot joints: one bone rotates in a ring of another bone that does not move • Ex: turning your head • Ball-and-socket joint: consists of a bone with a rounded end that fits into a cuplike cavity on another bone • Ex: your legs and arms • Hinge joint: has a back-and-forth movement like hinges on a door • Ex: elbow, knees, fingers • Gliding joints: one part of a bone slides over another bone • Ex: wrists, ankles, vertebrae

8. Potential problems • Osteoporosis: a condition in which bones become brittle and fragile from loss of calcium • Arthritis: the most common joint problem • All forms begin with the same symptoms: pain, stiffness, and swelling of the joints