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

Major Organs of the Major Organs of the Skeletal SystemSkeletal System

Skull Clavicle Ribs

Humerus RadiusUlna

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.

•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 Different Kinds of Bone Tissueof Bone Tissue

Compact BoneBone tissue that does not have any visible

open spacesSpongy Bone

Bone tissue that has many open spacesSpongy bone provides most of the strength

and support for a bone. It acts like the trusses of a bridge.

Bone MarrowRed marrow, found in spongy bone, produces

red blood cellsYellow marrow, found in the central cavity of

long bones, stores fat

•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 Three Types of JointsJoints

• 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.

                                                       

SlidinSliding g

JointJoint

                                                       

Ball-and-Ball-and-Socket JointSocket Joint

                                                   

Hinge JointHinge 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.