The Skeletal System

Five Major Functions1. Gives shape and support to body2. Protects your internal organs

1. Ex: ribs protect heart, skull protects brain

3. Major muscles are attached to bone and help them move

4. Blood cells formed in center of bones in soft tissue called red marrow

5. 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