「The diaphysis (/da??æf?s?s/[1][2]) is the main or midsection (shaft) of a long bone. It is made up of cortical bone and usually contains bone marrow and adipose tissue (fat).
It is a middle tubular part composed of compact bone which surrounds a central marrow cavity which contains red or yellow marrow. In diaphysis, primary ossification occurs. Ewing's sarcoma tends to occur at the diaphysis.[」
