Bones, cartilage, and the special structures that connect them make up your skeletal system

Major Organs of the Skeletal System SkullClavicle RibsHumerus RadiusUlna PatellaFemur TibiaFibula Pelvic Vertebral girdle column

Protection Storage Movement Blood Cell Formation

Protection Your heart and lungs are shielded by your ribs Your spinal cord is protected by your vertebrae Your brain is protected by your skull

Storage Bones store minerals that help the nerves and muscles function properly Your arm and leg bones also store fat that can be used for energy

Movement Skeletal muscles pull on the bones to produce movement Without bones, you would not be able to sit, stand, walk, or run

Blood Cell Formation Some of your bones are filled with a special material that makes blood cells

A bone may seem lifeless, but it is a living organ made of several different tissues. Bone is composed of connective tissue and minerals that are deposited by living cells called osteoblasts.

Different Kinds of Bone Tissue Compact Bone Bone tissue that does not have any visible open spaces Spongy Bone Bone tissue that has many open spaces Spongy bone provides most of the strength and support for a bone. It acts like the trusses of a bridge. Bone Marrow Red marrow, found in spongy bone, produces red blood cells Yellow marrow, found in the central cavity of long bones, stores fat

Growing Bones Most bones start out as a soft, flexible tissue called cartilage When you were born, you had little true bone As you grow, the cartilage is replaced by bone During childhood, growth plated of cartilage remain in most bones, providing a place for those bones to continue to grow.

The place where two or more bones connect is called a joint Some joints allow a lot of movement, while other joints are fixed. Joints that have a wide range of movement tend to be more susceptible to injury that those that are less flexible.

Three Types of Joints Sliding Joint –Sliding joints allow bones in the hand to glide over one another, giving some flexibility to the area. Ball-and-Socket Joint –Like a joystick on a computer game, the shoulder enables your arm to move freely in all directions. Hinge Joint –Like a hinge on a door, the knee enables you to flex and extend your lower leg.

Sliding Joint

Ball-and-Socket Joint

Hinge Joint

Joints are kept together with strong elastic bands of connective tissue called ligaments. A strained ligament will usually heal with time, but a torn ligament will not. A torn ligament must be repaired surgically Cartilage helps cushion the area where two bones meet If cartilage wears away, the joint becomes arthritic.