Flat Bones

Flat bones are a type of bone that protects internal organs. The skull, ribs, and sternum are all made from flat bones. These bones are constructed in a sandwich-like manner, with hard compact bone on the outside and spongy bone on the inside. Red bone marrow is contained within the spongy bone.

The hard outer layer provides protection from direct forces, while the spongy bone center allows these bones to absorb forces coming from different directions as well. The combination of compact and spongy bone is important because flat bones have numerous muscle attachment points that pull in different directions, so they need to be able to withstand forces in different directions.

For example, the skull is made of flat bones and irregular bones. Muscles attach to the skull at different locations. Some muscles allow us to open our mouths and bite down with force. Other muscles are used for smiling, yawning, and lots of facial expressions.

Figure 1: The skull is made from flat bones.