The Skeletal System

Five Major Functions Gives shape and support to body Protects your internal organs Ex: ribs protect heart, skull protects brain Major muscles are attached to bone and help them move Blood cells formed in center of bones in soft tissue called red marrow Major quantities of calcium and phosphorus compounds are stored

Bone structure Bones can have different sizes, shapes, Bone surface covered with periosteum Small blood vessels in periosteum carry nutrients to bone Two different bone tissues Compact bone Spongy bone

Compact Bone Directly under periosteum Hard, strong layer that gives bones strength Framework containing calcium phosphate Living tissue of bone cells and blood vessels that keeps bones from being too rigid, brittle, or easily broken

Spongy Bone Located towards end of long bones Has many small, open spaces that make bones lightweight Inside cavities and spaces in spongy bones, substance called marrow Some marrow yellow and composed of fat cells Red marrow produces red blood cells

Cartilage Smooth, slippery, thick layer of tissue that covers the end of bones No blood vessels or minerals Flexible and important in joints because it acts as shock absorber Makes movement easier by reducing friction

Bone Formation Before being born, baby skeleton made of cartilage Bone cells called osteoblasts deposit calcium and phosphorus in bones, making the tissue hard At birth, we have >300 bones, but as we develop, bones fuse and only have 206 Bone tissue always being formed Osteoblasts build bone Osteoclast breaks down bone

Joints Any place where two or more bones come together Bones kept far enough apart by cartilage Classified as immovable or movable Ligaments tough band of tissue that holds bones in place at joints

Immovable joints Allows little or no movement Joints of skull and pelvis are immovable

Movable Joints All movement requires movable joints Several types Pivot Ball and socket Hinge gliding

Pivot Joint One bone rotates in a ring of another bone that does not move Ex: turning your head

Ball and Socket Bone with rounded end that fits into a cuplike cavity on another bone Provides wider range of motion Why your arms and legs can swing in almost any direction

Hinge Back and forth movement like hinges on door Ex: elbows, knees, fingers

Gliding Joint One part of a bone slides over another bone Move in back and forth motion and are used most in body Ex: wrist, ankle

Joint Problems Arthritis pain, stiffness, and swelling of joints Osteoarthritis results when cartilage breaks down because of years of use Rheumatoid arthritis ongoing condition in which the body’s immune system tries to destroy its own tissues