Bones

The skeleton

The human skeleton is made up of 206 bones, including bones of the:

• Skull – including the jaw bone
• Spine – cervical, thoracic and lumbar vertebrae, sacrum and tailbone (coccyx)
• Chest – ribs and breastbone (sternum)
• Arms – shoulder blade (scapula), collar bone (clavicle), humerus, radius and ulna
• Hands – wrist bones (carpals), metacarpals and phalanges
• Pelvis – hip bones
• Legs – thigh bone (femur), kneecap (patella), shin bone (tibia) and fibula
• Feet – tarsals, metatarsals and phalanges.

Bone types

There are four different types of bone in the human body:

• Long bone – has a long, thin shape. Examples include the bones of the arms and legs (excluding the wrists, ankles and kneecaps). With the help of muscles, long bones work as levers to permit movement.
• Short bone – has a squat, cubed shape. Examples include the bones that make up the wrists and the ankles.
• Flat bone – has a flattened, broad surface. Examples include ribs, shoulder blades, breast bone and skull bones.
• Irregular bone – has a shape that does not conform to the above three types. Examples include the bones of the spine (vertebrae).Bone tissue

The different layers of bone tissue include:

• Periosteum – the dense, tough outer shell that contains blood vessels and nerves
• Compact or dense tissue – the hard, smooth layer that protects the tissue within
• Spongy or cancellous tissue – the porous, honeycombed material found inside most bones, which allows the bone to be strong yet lightweight
• Bone marrow – the jelly-like substance found inside the cavities of some bones (including the pelvis) that produces blood cells.