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

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

4. 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.

5. Function of Bones
Protection
Storage
Movement
Blood Cell Formation

6. 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

7. 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

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

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

10. 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.

11. 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

13. 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.

14. 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.

15. Sliding Joint
                                                       

16. Ball-and-Socket Joint
                                                       

17. Hinge Joint
                                                   

18. 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.