The Skeleton and bone types

On this page you will find simple to follow explanations of the human skeleton, types of bone and bone formation.

 The Functions of the Skeleton

The skeleton consists of all of the bones within the human body. The skeleton has five main functions:

• Support: The skeleton supports the soft tissues of the body as it forms a rigid framework to which our muscles, tendons, ligaments etc attach.
• Shape: The overall shape of our bodies is mostly due to our skeletons. e.g. your skeleton determines if you are short or tall by how long your bones are
• Protection: Our bones are very strong and can provide protection to the vital organs. e.g. the skull protects the brain, and the ribs and sternum protect the heart and lungs
• Movement: Our bones are levers which are pulled by the muscles to cause movement
• Making blood cells: Inside long bones is a substance called bone marrow, which makes new blood cells.

Here is a diagram of the skeleton, with all of the main bones labeled:

 Types of Bones

Bones are classified into four groups:

Long Bones	Have a body longer than it is wide Have a hard outer casing with spongy bone in the centre Bones such as the Femur, Humerus and Metatarsals
Short Bones	Are roughly as wide as they are long Contain large amounts of bone marrow to make blood vessels Bones such as the Carpals and Tarsals in the wrist and foot
Flat Bones	Strong, flat pieces of bone Their main functions are protection and muscle attachment Bones such as the cranium (skull) and scapula (shoulder blade)
Irregular Bones	Do not fit into any of the other categories and often have an unusual shape Bones such as the Vertebrae, Sacrum and Mandible

Bone Formation

Ossification is the process by which cartilage is turned to bone.

• When we are born our bones are actually cartilage!
• The process of ossification turns the cartilage to bone. This can take up to a few years for some bones!
• Bones are made up of several layers. The outermost layer is called the periosteum
• There is then an outer layer of strong compact (hard) bone
• The centre of bones contains spongy (cancellous) bone
• Some spongy bone contains red bone marrow, which makes red blood cells
• The marrow cavity contains yellow marrow which makes white blood cells