Long bones - like thigh bones - have a shaft composed of compact bone. At the centre of this shaft lies the medullary canal, which contains yellow bone marrow.

The ends of long bones have a two-part structure. A mass of spongy bone - which provides cushioning if the bone is knocked - is surrounded by a thin layer of compact bone.

The official name for the shaft of a long bone is the diaphysis. The two ends of a long bone are called the epiphyses (singular: epiphysis).

Short bones and irregular bones have a similar structure to the epiphyses of long bones. They consist of a mass of spongy bone, surrounded by a shell of compact bone. s

In flat bones, a layer of spongy bone is sandwiched between two layers of compact bone - rather like an ice cream wafer!