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

Major Organs of the Skeletal System Skull Clavicle Ribs Humerus Radius Ulna Patella Femur Tibia Fibula Pelvic Vertebral girdle column

When you were born, your skeleton had around 350 bones. By the time you become an adult, you will only have around 206 bones. This is because, as you grow, some of the bones join together to form one bone.

Function of Bones 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

What's in a Bone? 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

What's the Point of a Joint? 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 Ball-and-Socket Joint Hinge 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                                                    

Bone to Bone 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.